Employment 4. Topographical Anatomy and Operative Surgery of Thoracic Wall and Mammary Gland. Topographical Anatomy and Operative Surgery of Lungs and Organs of Anterior and Posterior Mediastium. Topographical Anatomy and Operative Surgery of Heart and Pericardial Sac.
THORAX
Bony Thorax The thorax is shaped like a truncated cone, which is flattened from before backward and contains important organs of respiration, circulation and digestion. Its anterior wall is the shortest and is formed by the sternum and the anterior portions of the first 10 pairs of ribs, with their corresponding costal cartilages. The lateral walls are formed by the ribs, which slope obliquely downward and forward; the posterior wall is made up of the 12 thoracic vertebrae and the ribs as far as their angles.
FIG. The bony thorax. (A) Anterior view, with the conventional longitudinal lines shown. (B) Sibson’s fascia, which forms the diaphragm for the superior aperture.
At birth and about 2 years thereafter the thorax is circular and does not resemble the oval-shaped adult thorax. Because of this difference, the adult thorax may be increased in thoracic breathing, but this is impossible in the child, since the circumference remains constant in the latter. For this reason, breathing in the first 2 years of life is almost entirely abdominal (diaphragmatic), but as the individual grows older, breathing becomes intercostal (thoracic). Because children’s breathing is not thoracic, they are supposed to be more susceptible to postoperative pneumonia. The child restricts his abdominal movements because of pain, thereby interfering with excursions of the diaphragm; this results in poorly aerated lungs, which become filled with accumulated secretions. The child’s thorax may be referred to as the “normal” barrel chest of early life. The thorax has a small kidney-shaped superior aperture and a large irregular inferior one.
Superior Aperture. This is the inlet and measures approximately 2 by
Inferior Aperture. This is the outlet of the thorax. It is large and irregular and bounded by the 12th thoracic vertebra, the lowest ribs, the 7th to the 12th costal cartilages and the xiphisternal joint. It is much wider than the inlet and is occupied by the diaphragm. Certain conventional longitudinal lines are used for the purpose of description and orientation. They run parallel with the long axis of the body and are:
1. Midsternal line—bisects the sternum and corresponds to the midline of the back.
FIG. Posterior view of the bony thorax.
2. Mammary line—this is dropped from the inner aspect of the clavicle and usually passes through the nipple.
3. Parasternal line—lies midway between the midsternal and the mammary lines.
4. Anterior axillary line—this runs through the anterior axillary fold.
5. Posterior axillary line—passes through the posterior axillary fold.
6. Midaxillary line—this is dropped from the middle of the axillary space.
7. Scapular line—this runs through the apex of the inferior angle of the scapula.
8. Paravertebral line—opposite the tips of the transverse processes of the vertebrae (used in radiology).
RIBS (COSTAE) The 12 pairs of ribs form a series of obliquely placed bony arches which constitute the greater part of the wall of the thoracic cage. They overhang the upper part of the abdomen, articulate with vertebrae posteriorly and end in costal cartilages anteriorly. They increase in length from the 1st to the 7th and then become progressively shorter.
True Ribs. The first 7 pairs are called true ribs because their cartilages articulate with the sternum.
False Ribs. The cartilages of the last 5 pairs are known as false ribs.
Floating Ribs. The 8th, the 9th and the 10th pairs end by turning upward to join the costal cartilage above, but the 11 th and the 12th are free at their extremities and are known as floating ribs. All the ribs can be felt through the overlying soft structures, with the exception of the 1st, which is hidden by the clavicle, and occasionally the 12th. The 1st rib may be absent or very short. The 2nd rib always can be identified where its cartilage reaches the sternum at the sternal angle. Therefore, when it is necessary to locate a given rib, the 2nd should be found, and the succeeding ribs should be counted from above downward, following a line about
The so-called typical rib articulates with 2 vertebrae, namely, the vertebra to which it corresponds numerically, and the vertebra above this. It has a head, a neck, a tubercle and a shaft; the last-named structure has an angle posteriorly and a costal groove interiorly. The head presents a kidneyshaped articular surface which is divided into two facets by a transverse crest. These facets articulate with the contiguous facets on the lateral aspect of the bodies of the 2 adjacent vertebrae. From the intervening crest or ridge, an interarticular ligament passes to the intervertebral disk. The neck is constricted and is about
FIG. The bony thorax as viewed from above. The small insets show the transverse section of a child’s thorax as compared with that of an adult.
with the corresponding transverse process, and above and behind this is a rough areafor the lateral costotransverse ligament. The shaft is compressed laterally, giving it internal and external surfaces, which are separated by superior and inferior borders. It not only has a curved but also a twisted appearance. The curvature is greatest posteriorly, and its maximum point is known as the angle, which is marked by a ridge on its external surface, the latter being smooth and covered with muscles. The internal surface is also smooth but is covered with pleura; the superior border is rounded, and the inferior border is grooved. The costal groove contains the intercostal vessels and nerves, which are protected by its sharp overhanging outer margin. The anterior {sternal) extremity of the shaft is oval in shape and concave for the reception of the costal cartilage.
Special Ribs. This group includes the 1st, the 2nd, the 10th, the 11th and the 12th; they are so-called because they possess special features by which they may be identified. The 1st rib has been called the “superlative” rib because it is the highest, broadest, strongest, flattest, most curved and, with the occasional exception of the 12th, the shortest of all the ribs. Its angle coincides with its tubercle. It is placed almost horizontally so that its surfaces face upward and downward, and it articulates with only one vertebra. The head is small and has only one facet, which articulates with the body of the 1st thoracic vertebra; the neck is relatively long. The tubercle is fairly large and articulates with the 1st thoracic transverse process. The lower surface of this rib is smooth and devoid of any important landmarks, but the upper surface presents several important features. A roughened area is present for the insertion of the scalenus medius and the origin of the first digitation of the serratus anterior. The front of this rib is crossed by a wide shallow groove, which lodges the subclavian artery. Along the inner border and anteriorly, this arterial groove is limited by the scalene tubercle (Lisfranc) where the scalenus anterior muscle inserts. The size of the tubercle varies, in some cases forming a prominent point while in others it is barely recognizable. Anterior to this, a shallow groove is noted, which lodges the subclavian vein. The rib does not contain a costal groove; its lower smooth surface is covered with pleura, and its sternal end is enlarged to receive the lateral extremity of the first costal cartilage. The 2nd rib is intermediate in size and shape; it lies between the 1st and the lower ribs; although sharply curved, it is not twisted. Its angle is just lateral to its tubercle, and its surfaces are oblique. This rib has a poorly marked costal groove and a rough elevatioear the middle of its outer surface where the lower part of the first digitations and the whole of the second digitations of the serratus anterior attach. The scalenus posterior is attached behind this point. The 10th rib resembles a typical rib but is shorter, and its head usually presents only one facet for the body of the 10th thoracic
FIG. A typical rib: (A) the individual parts of the rib are identified; (B) the nutrient artery enters just beyond the tubercle.
vertebra. It is the “uncertain” rib, since it may articulate with the 9th cartilage, which may be connected to it by a ligament or may remain free as a floating rib. The 11th rib is short and has only a single facet on its head for the 11th thoracic vertebra; it does not have a neck or tubercle, and its costal groove is difficult to see. The 12 th rib is very short and has only one facet on its head; it lacks a tubercle, an angle and a costal groove. It should be noted that the inner surfaces of both the 11th and the 4th ribs look upward as well as inward.
The blood supply reaches each rib through its owutrient vessel which enters just beyond the tubercle and runs forward as far as the inner extremity of the bone . An additional supply is obtained from the periosteal vessels. The periosteum of the ribs strips easily from the bone, but that of the sternum does not. H. A. Harris has pointed out that no anastomosis occursbetween the vessels of the diaphysis and the epiphysis of the ribs and that the vessels of the former are virtually “end arteries.” Ossification resembles the long bones of the limbs and the bodies of the vertebrae, since it begins to take place in the 2nd fetal month. The process begins near the angle and continues in both directions but fails to reach the sternal end, resulting in costal cartilages.The ribs, the vertebrae, the sternum and the diploe of the skull are filled with the red blood-forming marrow. It is in these bones and not in the limbs that the blood elements are formed after puberty.
The costal cartilages continue the costal arches in front of the anterior extremities of the ribs. The first 7 cartilages are continued forward and articulate with the sternum. The 8th, the 9th and the 10th anterior extremities end by joining with the costal cartilage above.These form a continuous cartilaginous ridge, known as the subcostal margin, which forms a part of the inferior aperture of the thorax. The cartilages increase in length from the 1st to the 7th, and below this point they diminish. When traced downward, the intervals between the cartilages diminish.
FIG. The 1st and the 2nd ribs as seen from above; the muscular attachments have been identified.
STERNUM (BREAST BONE) The sternum is an elongated flat bone which is situated in the midventral line of the thorax and forms the anterior boundary of the thoracic cavity. It is shapedmuch like an old Roman sword, having a short handle called the manubrium, a longer blade called the body and a small piece of cartilage at its lower end known as the xiphoid (ensiform) process. In early fetal life the sternum is represented by right and left cartilaginous plates with which the rib cartilages articulate. Later, these two plates fuse, but this may be incomplete, resulting in a foramen.
MUSCLES WHICH ATTACH TO THE STERNUM
1. Vector alls major—to the marginal area of the anterior surface of the anubrium and the body.
2. Sternocleidomastoid—to the anterior surface of the manubrium.
3. Sternohyoid—to the posterior surface of the manubrium.
4. Sternothyroid—to the posterior surface of the manubrium on a slightly lower level than the forementioned muscle.
5. Transversus thoracis—to the posterior surface of the last segment of the body of the xiphoid.
6. Diaphragm—to the posterior surface of the xiphoid.
7. Aponeuroses of the external oblique, the internal oblique and the transversus muscles —to the lateral border of the xiphoid.
8. Rectus abdominis—to the anterior surface of the xiphoid. Fractures of the sternum are rare, but when present they occur most frequently at the junction of the manubrium with the body; at this point the bone is thinnest. The ligamentous attachments usually protect underlying structures, but at times the upper fragment may pass behind the lower and compress the trachea or injure the aorta.
FIG. The sternum. Muscular origins have been colored red, and insertions blue. (A) Front view; the 4 sternebrae and the articulating facets are shown. (B) Side view. The formation of the sternal angle is seen best from this view. (C) Posterior view. This surface is smooth and is related to the pericardium and the pleurae. (D) The 2 embryonic cartilaginous plates from which the sternum is formed. (E) Side view to show the thoracic levels of the jugular notch, the manubriosternal joint and the xiphoid process.
FIG. The sternoclavicular joint. A coronal section is shown on the left half of the illustration. A sternocostal joint is also shown.
INTERCOSTAL SPACES MUSCLES The muscles which are associated with the intercostal spaces are the external intercostal, the internal intercostal and the transverses thoracis. Corresponding intercostal nerves and vessels supply them.
The external intercostal muscle fibers are the thoracic representative of the external abdominal oblique. They pass downward and forward between adjacent borders of 2 ribs and become membranous in the intercartilaginous portion of the space where they assume the name of the anterior intercostals membrane. The fleshy interosseous parts extend as far as the tubercles of the rib posteriorly.
The internal intercostal muscle is the thoracic representative of the internal abdominal oblique. These fibers run in the opposite direction to those of the external. The fleshy fibers extend from the sternal ends of the spaces as far as the angles of the ribs posteriorly; here they become membranous and continue as the posterior intercostal membrane, which merges with the anterior costotransverse ligaments.
The transversus thoracis muscle is the thoracic representative of the transversus abdominis and should be considered as having 3 parts: the sternocostalis, the innermost intercostal and the subcostal. The sternocostalis part has also been referred to as the transversus thoracis and the triangularis sterni; it is the most constant part of the muscle and is located on the back of the anterior wall of the thorax. It arises from the back of the xiphoid and the body of the sternum as high as the 3rd costal cartilage and inserts into the costochondral junction from the 2nd to the 6th rib. Its lowest fibers are horizontal and continuous with the uppermost part of the transversus abdominis muscle. The muscle has three important features: it fails to cross the first two intercostals spaces; the internal mammary vessels descend in front of it; the pleura is immediately behind it. These relations are important during ligation of the internal mammary artery. The innermost intercostal part is incomplete and variable and passes from rib to rib deep to the internal intercostal. Its fibers pass in the same direction as those of the internal intercostal and can be distinguished from it only when separated by the intercostals nerves and vessels. Occasionally, some of the bundles skip over a rib and insert on the rib below. By its fascia it is connected to the sternocostal part anteriorly and the subcostal part posteriorly. The subcostal (part) muscle is made up of slips that vary greatly in size and number. They lie on the internal surface of the lower ribs near their angles and may be looked upon as parts of the innermost intercostals which cover two intercostal spaces. There are 11 intercostal spaces: the upper 9 are closed, but the lower 2 remain open anteriorly. They are all wider in front than behind; the widest is the 3rd, followed by the 2nd and then the 1st. The 7th, the 8th,
FIG. An intercostal space; a diagrammatic presentation of two views, showing the relations of muscles, vessels and nerves. In the posterior part of the space, the nerve is situated almost between the ribs, but from the angles of the ribs forward, it lies in the subcostal groove.
FIG. The transversus thoracis muscle. This has 3 parts, namely, the sternocostalis,
the innermost intercostal and the subcostal. The sternocostalis is the most constant in position, and the innermost intercostal the least constant. (A) Anterior wall viewed from within; (B) posterior wall viewed frorp within.
the 9th, and the 10th are very narrow. The spaces are wider in inspiration than in expiration, and their width can be increased by bending the body to the opposite side.
The subcostal groove in a typical rib is situated on the deep surface of its sharp lower border. It contains from above downward the respective intercostal vein, artery and nerve (V.A.N.). In the posterior part of the space the nerve is situated midway between the ribs, but from the angles of the ribs forward it lies in the subcostal groove.
BLOOD VESSELS
Intercostal Arteries. Since there are 11 intercostal spaces, there must be 11 intercostal arteries. These originate posteriorly and are designated as the posterior .intercostals arteries. The anterior intercostal arteries arise from the internal mammary. Not all 11 posterior arteries arise from the aorta, since only the lower 9 have this origin; the upper 2 are branches of the highest intercostal, a branch of the costocervical trunk of the subclavian. The right aortic intercostals are longer than the left because of the position of the aorta to the left of the vertebral column. Each vessel divides into anterior and posterior branches. The posterior supplies the spinal canal, the back musculature and the overlying skin. It is the anterior branch of the posterior intercostals artery which passes forward in the subcostal groove. The intercostal vessels and their corresponding nerves pass anteriorly in the plane between the innermost intercostals and the internal intercostal muscles. The lower intercostal vessels and nerves occupy a corresponding plane in the abdominal wall. Anteriorly, the vessel divides into superior and inferior (collateral) branches which unite with those from the internal mammary artery. Since the lowest two intercostal spaces remain open, the lowest two intercostal arteries continue on into the abdominal wall.
The subcostal artery is the same as any intercostal artery, but since there is no 12th space, it assumes a separate name.
The internal mammary artery arises from the undersurface of the first portion of the subclavian artery opposite the thyrocervical trunk. It descends behind the innominate vein and the sternoclavicular articulation and then passes vertically downward on the deep surface of the thoracic wall about YA inch from the outer border of the sternum. It is covered by skin, fascia, pectoralis major muscle, anterior intercostal membrane, internal intercostal muscle and costal cartilage. In the region of the 6th intercostals space, it ends by dividing into superior epigastric and musculophrenic branches. Opposite each of the upper 6 intercostal spaces the internal mammary gives off perforating branches which pass forward through the intercostal spaces. In females the 2nd and the 3rd perforating branches are much larger, since they supply not only the overlying muscles and skin but the mammary gland as well. Corresponding to each perforating artery, the internal mammary also gives rise to 2 anterior intercostal arteries. These small vessels pass laterally, one lying near the lower border of the rib above, and the other lying near the upper margin of the rib below; they anastomose with the posterior intercostals. Therefore, each intercostal space has 3 intercostal arteries (1 posterior and 2 anterior); however, this is not true for the lowest 2 spaces, since they remain open and have no anterior branches. Of surgical importance is the fact that the internal mammary artery lies directly on the pleura in the first 2 intercostal spaces. Below this level the transversus thoracis separates the vessel from the pleural membrane. Therefore, in order to avoid injury to the pleura, it is advisable to ligate the vessel below the first 2 interspaces. The vessel also supplies a slender branch, the pericardiophrenic, which accompanies the phrenic nerve. Because of its close relation to the nerve, the artery may be injured in the operation of phrenic avulsion and produce a hemorrhage large enough to necessitate ligation of the internal mammary artery.
The superior epigastric artery continues in the original direction of the internal mammary; it descends through the diaphragm and enters the rectus sheath to anastomose with the inferior epigastric (external iliac). The musculophrenic passes downward and laterally along the costal margin of the diaphragm which it perforates. It ends, much reduced in size, opposite the last intercostals space and supplies intercostal branches to spaces 7, 8 and 9. Ligature of the internal mammary artery is performed through a transverse incision in the anterior end of the 3rd interspace. The pectoralis major is divided in the line of its fibers, and the anterior intercostal membrane is exposed. This is incised, exposing the internal intercostal muscle. The vessel and its veins are found lying between the internal intercostal and the transversus thoracis (sternocostal part) muscles.
The internal mammary veins (venae comitantes of the internal mammary artery) unite opposite the 3rd costal cartilage, or a little lower, to form a single venous trunk which ascends along the medial side of the artery and enters the innominate vein at the thoracic inlet. These veins possess numerous valves and receive branches from the anterior intercostal veins of the upper 6 spaces, perforating branches, muscular branches, mediastinal, pericardial and thymic veins as well as the superior epigastric and musculophrenic venae comitantes. The internal mammary vessels are covered in their lower portions posteriorly by the transversus thoracis muscle, but in the upper part are in direct contact with the parietal pleura. The internal mammary vessels are crossed anteriorly by the intercostal nerves and are associated with lymph glands.
ARRANGEMENT OF THE 12TH SPINAL NERVES
The spinal nerves (Fig. 183) are arranged segmentally and are attached to the spinal cord by 2 roots: an anterior which is motor (efferent) and a posterior which is sensory (afferent). The posterior root has a ganglion on it. These roots leave the vertebral canal via the intervertebral foramina and immediately join to form a spinal nerve. Since this nerve has both sensory and motor fibers, it is spoken of as a mixed nerve; it divides into anterior and posterior rami. The anterior rami are larger and have a tendency to form plexuses (cervical, brachial, lumbar, sacral and pudendal), but the smaller posterior rami supply the muscles of the back and, in
addition, the overlying skin.
An intercostal nerve is the anterior nerve ramus. There are 12 pairs of such thoracic or intercostal nerves, 11 of which are truly intercostal and 1 subcostal. The 12th is the subcostal since it has to run its course in the abdominal wall and not in an intercostals space. The 1st intercostal nerve also differs somewhat because the greater part of it goes into the formation of the brachial plexus. Each nerve sends a white ramus communicans to a corresponding sympathetic ganglion and receives a gray ramus communicansfrom it. A typical intercostal nerve continues forward and supplies muscular and two cutaneous branches. The cutaneous branches are: (a) the lateral cutaneous nerve, which emerges in the midaxillary line, divides into anterior and posterior branches and supplies the side of the chest; (b) the anterior cutaneous nerve, which is the termination of the intercostal, appears at the inner end of an intercostal space, where it supplies the skin over the sternum and the front of the chest. Since the 1st thoracic nerve is mainly given to the formation of the brachial plexus, it is very small and supplies neither lateral nor anterior cutaneous branches. The 2nd intercostals nerve has lateral and anterior cutaneous branches, but its lateral branch does not divide in two, since it crosses the axilla as the intercostobrachial nerve, which supplies the skin of the posteromedial aspect of the arm as far as the elbow. The 7th supplies the region of the epigastrium; the 10th, the umbilical region; and the 12th innervates that region which is situated midway between the umbilicus and the pubis. Nerves 2, 3, 4, 5and 6 run typically intercostal or thoracic courses, but 7, 8, 9, 10 and 11 travel partly in the thoracic and partly in the abdominal wall, thus taking a thoracico-abdominal course. The typical thoracic nerves 2 to 6 are separated from the pleura by the innermost intercostals muscle and the transversus thoracis. After supplying the intercostal muscles, they cross in front of the internal mammary artery and in company with the perforating artery, pierce the internal intercostal muscle, the anterior intercostal membrane and the pectoralis major, terminating as an anterior cutaneous nerve of the thorax.In the abdominal course, the thoracicoabdominal nerves (7th to 11th) leave their interspaces between the diaphragm and the transversus abdominis and pass between the internal oblique and the transverses abdominis to the back of the rectus sheath. After piercing the sheath they travel in front of the superior or inferior epigastric artery, supply and pierce the rectus abdominis muscle and continue to the anterior abdominal wall; finally, in company with a cutaneous branch of the epigastric artery they end as anterior cutaneous nerves of the abdominal wall. The intercostal and subcostal nerves supply the following muscles: external and internal intercostals, subcostals, transverses thoracis, levator costarum, external and internal oblique, transversus abdominis, rectus abdominis, and pyramidalis. Dorsally, these nerves supply the serratus posterior superior and the serratus posterior inferior. The upper 6 intercostal nerves do not reach the midline of the body but end at the inner side of the intercostal space. This is of some diagnostic importance, since a swelling
FIG. 184. The internal mammary vessels.
over the center of the sternum could not be a cold abscess which has tracked around from the spine along the course of the intercostals nerve, because such a collection could not extend beyond the lateral edge of the sternum. These intercostal nerves run an oblique course, but the area supplied by any one of them is horizontal. Head has shown that before anesthesia is evident in the region of their nerve distribution, at least 3 contiguous nerves must be divided since the overlapping from the nerve above and the nerve below would compensate for any injury to asingle nerve.
Breast (Mammary Gland)
EMBRYOLOGY AND EMBRYOLOGIC MALFORMATIONS
Although the mammary glands do not come into use until adult life, nevertheless, they are the first of all the glands which arise from the epidermis to appear during the development of the embryo. In a 6-weeks-old human embryo an ectodermal ridge, known as the milk line or primary ridge, is noted. This thickening extends along the body wall on either side from the axilla to the groin. In the human it atrophies, but a small portion remains in each pectoral region, which becomes the mammary gland. Since these ridges consist of tissue which is potentially mammary, failure of their normal disappearance will result in the persistence of accessory breast tissue. Such tissue remains along the line and can appear anywhere from the axilla to the inner aspect of Scarpa’s triangle. The rare presence of accessory breast tissue in locations such as the gluteal region and the shoulder can be explained only by an ectopic placement of the milk ridge. Normally, that portion of the ridge
FIG. The milk lines. These ridges consist of potential mammary tissue, and their failure to disappear would result in accessory breasts.
The congenital abnormalities which may occur are:
1. Polymastia. This condition presents more than one breast on one or both sides and is due to the persistence of part of the milk ridge. The accessory breast may be well developed or tiny, and instances have beeoted where these breasts have been used for suckling. As many as 10 have been recorded in one individual.
2. Polythelia. This condition is one in which supernumerary nipples are found over a given breast and not necessarily on the milk ridge.
3. Gynecomastia. This is the presence of a female breast or breasts in the male. Congenital absence, amastia, either unilateral or bilateral, has also been recorded. Unilateral amastia is believed to be due to pressure of an arm in utero against the pectoral region. When this exists the pectoral muscles on the affected side are also atrophic or absent.
MAMMARY GLAND PROPER (STRUCTURE AND FORM)
The mammary gland extends verticallyfrom the 2nd to the 6th rib inclusive and horizontally from the side of the sternum (parasternal) to the midaxillary line. The greater part of the breast, about two thirds, rests on the pectoralis major muscle; and the rest, about one third, on the serratus anterior. The breast is hemispherical in shape, but tonguelike processes may extend upward, downward or medially from it; the most common of such processes is the socalled axillary tail of Spence.
This is a prolongation of breast tissue from the upper outer part of the breast, which passes through an opening in the axillary fascia, called the foramen of hanger. Therefore, although the breast proper is superficial to the axillary fascia, the axillary tail is deep to this fascia. Such a process is in direct contact with the axillary glands; therefore, if it is enlarged it may be mistaken for an axillary tumor or for axillary lymph adenopathy.
FIG. Mammary gland.Blood supply.
FIG. Lymphatyc nodes and vessels of the mammary gland
Since the breast is a modified sebaceous gland, it lies in the superficial fascia and not upon or deep to it. The deep surface rests on the fasciae which cover the pectoralis major and the serratus anterior muscles. The gland is made up of lobes (usually 12) which are subdivided into lobules, and these in turn are composed of acini. The lobes are arranged like the spokes of a wheel which converge on the nipple, and each lobe is drained by a lactiferous duct; from 12 to 20 such ducts open onto the nipple. The organ is fixed to the overlying skin and the underlying pectoral fascia by fibrous bands known as Cooper’s ligaments. These are clinically important because cancer cells invade them and subsequently cause their contraction, which results in dimpling of the skin or fixation of the growth. By the same process, a malignant tumor may be fixed to the underlying pectoral fascia and then cannot be moved in the long axis of the muscle. The ducts open independently of each other on the surface of the nipple, and each has a dilated ampulla just before it ends. The nipple is conical in shape and usually is found in the 4th intercostal space. Its base is surrounded by a circular pigmented area called the areola, which has many small rounded elevations (cutaneous glands) known as the areolar glands of
VESSELS, NERVES AND LYMPHATICS
Arteries. The arterial supply is derived chiefly from two sources: namely, the anterior perforating branches of the internal mammary artery and mammary rami of the axillary or one of its main branches. Anson, Wright and Wolfer are of the opinion that no mammary branches are derived from the anterior intercostal arteries. The anterior perforating arteries are branches of the internal mammary. The first 4 or 5 of these supply the breast, but only 2, usually the 1st and the 4th (or the 2nd and the 3rd) are well developed; however, almost all of these vessels have a tendency to travel transversely and cephalad to the nipple. The lateral thoracic artery, a branch of the second part of the axillary, descends along the lateral margin of the breast and sends small branches into the gland, but its larger branches are distributed to the thoracic wall. Mammary branches of this latter vessel also have a tendency to travel transversely across the breast and in this way anastomose with the mammary rami of the perforating arteries. The thoraco-acromial artery, also a branch of part two of the axillary, is usually described as being one of the vessels which supply the breast tissue. This apparently is incorrect, since the pectoral branches of this vessel remain on the deep aspect of the pectoralis major, supply it and do not enter the gland. Therefore, blood is supplied to the breast from two arterial sources: (1) the anterior perforating branches of the internal mammary and (2) the lateral thoracic arteries. Since these vessels pass cephalad to the nipple and in a transverse direction, the blood supply of the gland is located mainly at its superomedial and superolateral aspects. Therefore, an incision into the breast should be placed below the nipple to preserve the
FIG. Cross section of an adult female breast: (A) the breast has been dissected layer by layer, (B) attachments of Cooper’s ligaments.
blood supply and to make the scar less visible. Since no major vessels reach the gland from its inferior aspect, plastic procedures, plastic procedures on the pendulous breast as well as diagnostic incisions into the breast should be placed in the inferior quadrants,
Veins. Although the main veins follow the arterial pattern just described, many of
FIG. The arterial supply of the breast: (A) The arterial supply of the breast is derived from two sources: anterior perforating branches of the intern al mammary artery and the lateral thoracic artery. (B) The thoraco-acromial artery supplies the pectoralis major muscle and not the breast.
the smaller veins resemble the lymphatics and form a plexus beneath the areola. These are especially visible in the lactating breast. Large veins pass from the plexus toward the periphery and end in the axillary and the internal mammary veins.
Lymphatics. The lymph drainage consists of 3 parts: cutaneous, areolar and glandular. The cutaneous lymphatics carry the lymph from the integument of the breast, with the exception of the areola and the nipple, and converge in collecting trunks, which flow into the axillary glands of the same side. At the inner quadrants, and especially those near the sternum, lymphatics may cross and terminate in the breast or axillary glands of the opposite side.
The areolar lymphatics drain the nipple and the areola and pass into the subareolar plexus of Sappey. The plexus is drained by two main lymph channels: one for the inner part and one for the outer. They usually unite into one main trunk, which passes to the anterior group of axillary glands. The anterior axillary (pectoral or superficial) set is really the main group and is placed under the anterior axillary fold, following the course of the lateral thoracic vein. These glands are found in the region of the 3rd rib. From this set the glands drain to the central axillary set, which is situated in the fat of the upper part of the axilla, under the axillary tuft of hair and along the inner border of the axillary vein. The intercostohumeral nerve passes outward between these glands, and enlargement of the latter may produce pressure on the nerve, resulting in pain along the axilla or inner border of the arm. From here the lymph vessels pass to the deep axillary glands, part of which form a lateral group which passes along the course of the axillary vein; the other part forms the apical group which has also been referred to as the infraclavicular glands. These glands lie behind the costocoracoid membrane. Therefore, it is impossible to free them adequately unless the whole region of the costocoracoid membrane is removed. The deep axillary glands become continuous with the deep cervical glands in the supraclavicular fossa. Although the above path is the usual one taken, there are other lymphatic zones of cancer spread. Some of the lymphatics from the upper and the outer quadrants of the breast form a trunk that pierces the pectoralis major muscle and directly enters the gland along the axillary vein, thereby short-circuiting the axilla. Lymphatics also leave the inner quadrant of the breast and reach the glands inside of the chest cavity, lying on each side of the internal mammary artery. Occasionally, a few vessels pass to the cephalic gland which lies in the deltopectoral groove. In some instances breast cancer may spread downward in the lymphatics to the epigastric region and there invade the abdominal wall. Development of metastases in the liver and in the pelvic cavity can be explained by such permeation. It is possible for cancer from one breast to spread across the midline to the other subpectoral plexus, then to the opposite axilla and finally to the opposite breast. The pectoral lymph plexuses should not be regarded as separate systems but rather as communicating networks.
Nerves. The nerve supply of the skin of breast is derived from the anterior and lateral branches of the 4th to the 6th intercostals nerves, which reach it by way of the 2nd to the 6th intercostals.
SURGICAL CONSIDERATIONS
BREAST ABSCESS Breast abscesses may be subcutaneous, intramammary or submammary. The incision for a subcutaneous or inframammary abscess should be so placed that it radiates from the nipple but never transversely across the breast. If the abscess is deeper, submammary or retromammary, this incision is not utilized, but instead a thoracomammary approach in the inframammary fold is used. This is the same incision that is utilized for benign tumors of the breast, since practically any portion of the gland can be examined through it. With the breast retracted upward and medially, the incision is placed in the pigmented line. Then it is carried down to the underlying muscle, and the breast is displaced upward. The necessary procedure is done, be it draining an abscess or removing a tumor. The breast is permitted to fall back into its normal position where it is sutured.
RADICAL MASTECTOMY Radical mastectomy can be outlined in 6 anatomic steps, each having 3 substeps. This is only a plan and may be altered to fit any standard technic. The plan is outlined as follows:
1. Incision: a. Coraco-umbilical line b. Mobilization of skin medially to the midline of the sternum c. Mobilization of skin laterally to the latissimus dorsi (posterior axillary fold)
2. Axillary Fascia Step: a. Incision of axillary fascia along the lower border of pectoralis major b. Division of the pectoralis major near its insertion, leaving the clavicular part intact c. Division and ligation of the thoracoacromial vessels and nerves
3. Clavipectoral Fascia Step: a. Incision into the clavipectoral fascia along the lower border of the pectoralis minor b. Division of the pectoralis minor muscle c. Insertion of the pectoralis minor utilized as an axillary vein splint
4. Axillary Vein Dissection: a. Clamp, cut and ligate all venous tributaries b. Axillary glands and fat dissected downward c. Subscapular vessels used as a guide to the thoracodorsal nerve
5. Posterolateral Dissection: a. Exposure of the subscapular muscle b. Exposure of the latissimus dorsi c. Exposure of rectus abdominis
6. Medial Dissection: a. Dissection of pectoralis major and minor muscles b. Clamp and ligate perforating vessels (especially Number 2) c. Remove mass en bloc and close
Incision. Many incisions have been advised; however, the one described extends from the coracoid process above, which is always palpable, to the umbilicus below, which is always visible. Forceps are placed in the breast, which is elevated,
and then traction is made laterally; the incision is placed along the coraco-umbilical line. Next, traction is made to the opposite side, and the incision is completed along the coraco-umbilical line. The lateral and medial skin flaps are formed; they extend medially past the midline of the sternum and laterally to the latissimus dorsi.
Axillary Fascia. The second step is the axillary fascia phase. This fascia provides a covering for the pectoralis major muscle. An
FIG. Transverse section through the thorax, showing paths of lymph drainage from the breast.
FIG.(Facing page). Radical mastectomy: (A) The incision extends around the breast from the coracoid process to the umbilicus. The musculature in this region is shown. (B) A finger is placed through an incision in the axillary fascia, it emerges at the claviculosternal groove of the pectoralis major and not at the deltopectoral groove. This permits the clavicular portion of the muscle to remain intact and in this way protects the cephalic vein. (C) A finger is placed through an incision in the clavipectoral fascia. The finger passes under the pectoralis minor muscle, which is severed close to the coracoid process. The thoracoacromial vessels have been divided and tied.
FIGURE (Caption on facing page.)
FIG. (Facing page). Radical mastectomy (Continued). (D) The axillary vein is exposed by dividing the axillary sheath. The vessels below this vein are ndividually identified, severed and tied, and the axillary fat and lymph glands are dissected distally. (E) The entire mass is dissected downward. The attachments of the pectoral muscles are divided, and the perforating vessels are cut and ligated. If possible, the long thoracic and thoracodorsal nerves are saved. The rectus sheath is exposed and at times removed. (F) Closure.
FIGURE. (Caption on facing page.)
incision is placed into the fascia along the lower border of the pectoralis major. he index finger of the left hand is placed through the defect and is guided, not to the deltopectoral groove, which seems natural, but rather to the claviculosternal groove, which is not as well marked. If the clavicular portion of the pectoralis major muscle remains intact, it protects the cephalic vein, which runs in the deltopectoral groove. In the course of the operation it might become necessary to ligate or remove the axillary vein; if the cephalic vein is intact, the venous return of the superior extremity will not be impaired. The pectoralis major is cut near its insertion, and its sterno-abdominal part is reflected medially. As the pectoralis major is reflected medially, the thoraco-acromial vessels and the anterior thoracic nerves appear as a neurovascular bundle along the medial border of the pectoralis minor. These are clamped, severed and ligated.
Clavipectoral Fascia. The third step is the clavipectoral fascia phase. This fascia provides the covering for the pectoralis minor muscle. It is incised along the lower border of the pectoralis minor, so that the index finger of the left hand may be slipped under it and around the muscle. The pectoralis minor is divided, but a small part is left attached to the coracoid process; this acts as a splint for the axillary vein. With both pectoral muscles divided and retracted medial and downward, the axilla is exposed and then is ready for dissection of its contents.
Axillary Vein Dissection. In the axillary vein phase, the axillary sheath which covers the vein is opened carefully, and the vascular branches below the vein are individually identified, cut and tied. These usually include the short thoracic vein, the lateral thoracic artery, the long thoracic vein, the subscapular vein, the lateral thoracic vein and the subscapular artery. The axillary lymph glands and fat are dissected downward. The subscapular vessels act as a guide to the thoracordorsal nerve, and the lateral thoracic artery is the guide to the long thoracic nerve. If possible, these nerves should be saved, but if they are involved they must be sacrificed.
Posterolateral Dissection. This is carried out next. After the axillary cleansing has been accomplished, the subscapular muscle, the teres major and the latissimus dorsi come to view; the rectus sheath is also exposed.
Medial Dissection. This is the final stage. The origins of the pectoralis major and minor are severed, the mass is retracted laterally and downward, and the erforating vessels are sought in the intercostal spaces; they are found close to the lateral margin of the sternum. These must be clamped, cut and ligated, with special mphasis being placed on perforating branch Number 2, which has been discussed thoroughly. The entire mass is removed en bloc, and the wound is closed. At times skin grafts may be necessary. Currently, supraradical mastectomy is advocated by some surgeons for carcinoma of the breast. These procedures vary according to one’s definition of “radical.” Some surgeons advocate internal mammary artery (lymph node) dissection, removal of the clavicle, the ribs, and/or the superior extremity. This has become an individual problem and decision.
Diaphragm
The word diaphragm is derived from the Greek “dia” (in-between) and “phragma” (fence). It is a dome-shaped, musculo-aponeurotic partition which is located between the thorax and the abdomen.
FIG. The diaphragm viewed from below. The central tendon consists of 3 lobes and is the site of insertion of the diaphragm. The 4 points of origin have been identified.
FIG. The diaphragm viewed from the left. The 3 main apertures are shown, and their thoracic levels are labeled.
DIAPHRAGM PROPER
Adult Diaphragm. This musculotendinous partition is located between the pleurae and the pericardium above and the peritoneal cavity below. When relaxed and viewed from below, it forms a dome-shaped roof for the abdomen. Its circumferential part is fleshy, and these muscle fibers curve upward and inward from every side to join the edges of an aponeurotic sheath called the central tendon. It is this tendon which acts as the site of insertion for the diaphragm. The central tendon is strong, its tendinous bundles passing in different directions and interlacing with one another, giving it a pleated appearance. At times it has a trilobite appearance. Its median part is wide and is called the median lobe; the extremities or horns of the tendon are referred to as the right and the left lobes. The latter is the narrower. The tendon is inseparably blended above with the fibrous layer of the pericardium.
Origin. The origin of the diaphragm is quite extensive and takes place at the circumference of the thoracic outlet. It is best to consider it as originating at 4 points: sternal, costal, the crura, and the medial and lateral arcuate ligaments. The sternal origin consists of short right and left slips from the posterior aspect of the xiphoid process which are separated from each other by a little areolar tissue. These fibers pass upward and backward to the anterior margin of the central tendon where they insert. The costal origin is extensive and rises at a very steep angle. It usually consists of 6 fleshy muscle bundles which arise from the deep surface of the lower 6 costal cartilages, interdigitating with the costal origin of the transversus abdominis muscle. These fibers insert into the lateral and anterior borders of the central tendon. The crura are long tapering bundles which are fleshy above and tendinous below. The right crus arises from the sides of the bodies of the upper 3 lumbar vertebrae and the intervertebral disks; the left arises from the upper 2 lumbar vertebrae. The medial fibers of the 2 crura decussate in front of the commencement of the abdominal aorta; the fibers of the right crus encircle the esophagus. Both crura ascend forward and reach the posterior border of the central tendon.
Ligaments. The lateral and medial arcuate ligaments (lumbocostal arches) are lateral to the crura. The medial arcuate ligament is the upper thickened border of the psoas fascia which stretches between the side of the body of the 2nd and the tip of the transverse process of the 1st lumbar vertebrae. The lateral arcuate ligament is the thickening of the anterior lamella of the lumbar fascia which extends from the tip of the first lumbar transverse process to the lower border of the last rib. From this origin, the muscle fibers arch upward to reach the posterior border of the lateral part of the central tendon.
Nerves. The nerve supply of the diaphragm is derived from the right and the left phrenic nerves (C3, C4, C5).
Arteries. The arteries that supply it are the pericardiophrenic, the inferior phrenic, the musculophrenic and the intercostals.
Actions. The diaphragm is the chief muscle of respiration and it is in the abdominal type of breathing that it plays its greatest role. When its fibers contract, they straighten out, so that the domelike appearance is lost. In deep inspiration, the central tendon descends for a short distance.
FORAMINA (OPENINGS)The continuity of the diaphragm is broken by 3 large apertures and several smaller ones. The large openings accommodate the aorta, the esophagus and the inferior vena cava. The thoracic levels at which these structures pass are: the inferior vena cava at the 8th thoracic, the esophagus at the 10th and the aorta at the 12th.
Aortic Opening. This is located in the median plane in front of the lower border of the 12th thoracic vertebra and between the crura. It is bounded anteriorly by a tendinous arch which connects the medial borders of the crura to each other. Through this orifice pass the aorta, the thoracic duct and the azygos vein. The thoracic duct and the azygos vein are covered by the right crus.
Esophageal Opening. This oval aperture lies opposite the 10th thoracic vertebra in front, to the left of the aortic opening and behind the central tendon. The descussating fibers seem to act as a sphincter for the cardiac end of the stomach and prevent itscontents from returning to the esophagus. In addition to the esophagus, it transmits the right and the left vagus nerves and the esophageal branches of the left gastric artery with its companion veins. In cirrhosis of the liver, when an obstruction to the portal system is present, these veins at the lower end of the esophagus become dilated and varicosed, and frequently rupture. The vagi do not run to either side of the esophagus but are situated so that the left vagus passes anteriorly and the right posteriorly. The left, being anterior, supplies the anterosuperior surface of the stomach, and the right innervates the posteroinferior. The position of this opening is somewhat variable, since it may be found in the median plane or even to the right of it and may be very close to the aortic opening.
Inferior Vena Cava Opening. This opening is wide, and about 1 inch to the right of the median line on a level with the 8th thoracic vertebra. It is in the central tendon between the right and the median lobes; as this tendon stretches when the diaphragm contracts, the flow of venous blood into the thorax is facilitated. The opening transmits the inferior vena cava, some branches of the right phrenic nerve and a few lymph vessels from the liver. The phrenic nerve first pierces the muscle and then supplies it on its abdominal surface. The numerous smaller orifices transmitting vessels and nerves found in the diaphragm are: (1) the superior epigastric vessels between the sternal and the costal origins; (2) the musculophrenic vessels, which pass between the slips from the 7th and the 8th costal cartilages; (3) the lower 5 intercostal nerves accompanied by small vascular twigs, which pass between the slips from the 7th costal cartilage down; (4) the last thoracic (subcostal) nerve and the subcostal vessels, which pass behind the lateral arcuate ligament; (5) the sympathetic trunk, which passes behind the medial arcuate ligament; (6) each crus is pierced by the great, the lesser and the least splanchnic nerves; and (7) the inferior hemiazygos vein pierces the right crus.
Costophrenic Recess. The costophrenic recess is that portion of the pleural cavity which is unoccupied by lung except after full inspiration. Here the diaphragmatic
pleura is in contact with the costal pleura. When in full inspiration, the inferior border of the lung insinuates itself into this recess, and retraction of the overlying intercostals spaces is seen externally as the diaphragm decends and opens the costophrenic recess.
SURGICAL CONSIDERATIONS
DIAPHRAGMATIC HERNIAS Abnormal openings through the diaphragm which permit herniation of abdominal viscera into the thoracic cavity constitute the most common lesions of this structure which require surgery. Diaphragmatic hernias are classified as congenital, acquired and traumatic. All the traumatic, and many of the congenital hernias have no sacs. Therefore, they are not true hernias, but it is convenient to adhere to common usage and utilize the term. Most of the congenital hernias pass through the pleuroperitoneal canal (Bochdalek) and have no sacs. The majority of acquired (nontraumatic) hernias are located at the esophageal hiatus and have sacs. Since the liver affords protection to the right half of the diaphragm, hernias are rarely found here.
Diaphragmatic hernioplasty may be accomplished through abdominal, thoracic or combined abdominal and thoracic incisions.
Interruption of the phrenic nerve on the involved side can be either temporary or permanent and is of value as a procedure performed preliminary to radical operative repair. It prevents spasm and movement of the muscle and causes relaxation of the hernial ring; hence, it is of value in the closure of the opening.
The transthoracic route rarely requires rib resection. The incision is usually placed in the 6th or the 7th intercostal space and extends from the costochondral junction backward to the posterior axillary line. The ribs are separated. At times reduction of the hernia may be impossible via this route, and then an abdominal incision becomes necessary for bimanual manipulation and replacement of the viscera. The opening in the diaphragm is closed by imbricating its margin. Usually, a double row of sutures is used, and then the individual incisions are closed in layers.
The abdominal route utilizes a long, left
FIG. The diaphragm seen from above. The 3 major orifices and the structures passing through them are shown.
rectus incision. The left lateral ligament of the liver should be cut so that the left lobe of the liver can be retracted. This affords excellent exposure. The herniated viscera are freed of adhesions and reduced; at times it becomes necessary to enlarge the hernial ring for this reduction. The opening in the diaphragm is closed, usually by an imbrication method using interrupted sutures.
FIG. Two approaches to a diaphragmatic hernia. Below the diaphragm: (A) long left rectus incision, (B) repair of hernial orifice. Above the diaphragm: (A) incision in 6th intercostal space, (B) repair of hernial orifice.
Pleural Cavities and Pleurae
VISCERAL AND PARIETAL PLEURAE The thoracic cavity is divided into right and left pleural cavities and a region situated between these called the mediastinum. The lung invaginates the pleural cavity so completely that only a potential space remains, and by this process the pleura becomes divided into visceral (lung) and parietal (wall) layers.
The visceral pleura invests the lung, dips into its fissures and adheres so firmly that it is impossible to strip it from lung tissue.
The parietal pleura is subdivided, according to location, into 4 parts: costal, cervical, diaphragmatic and mediastinal. The costal pleura lines the ribs and their cartilages, the sides of the vertebral bodies and the back of the sternum. This is the thickest of all the parietal pleurae and is separated from the thoracic wall by the thin endothoracic fascia. It is directly continuous above with the cervical pleura (cupola) which covers the apex of the lung. This portion of the pleura extends upward into the root of the neck behind the interval between the two heads of the sternocleidomastoid muscle. Posteriorly, it reaches the level of the head of the 1st rib, but anteriorly it rises about 1 1/2 inches above the sternal extremity of that rib. Hence, it is protected by the rib posteriorly but not so anteriorly. This is explained by the fact that ribs do not run horizontally but obliquely; there is a drop of about 1 1/2 inches between the vertebral and the sternal attachments of the 1st rib. The upper aspect of the cervical pleura is covered by a layer of connective tissue called Sibson’s fascia. This fascia forms the internal lining of the scalene muscles and spreads out, fanlike from the transverse process of the 7th cervical vertebra to the inner border of the 1st rib. It separates the pleura from the first part of the subclavian artery, the phrenic nerve and the internal mammary artery. The diaphragmatic pleura is thin and very adherent to the diaphragm; it covers that part of the diaphragm not covered by the diaphragmatic pericardium. It is continuous with the costal pleura laterally, but medially it becomes continuous with the mediastinal pleura. The diaphragmatic pleura meets the costal pleura in 2 places: behind the sternum (sternal reflection) and in front of the bodies of the thoracic vertebrae (vertebral reflection). At the point at which the visceral pleura meets the mediastinal layer of parietal pleura there forms a pleural passageway. The upper part of this passageway contains those structures constituting the root of(the lung (pulmonary vessels and bronchus). The lower part is empty; hence, its walls approximate each other and form the pulmonary ligament. Only after deep inspiration are the lungs and the parietal pleurae completely in contact with each other. In ordinary breathing the lungs are not completely expanded; therefore, the edges of the pleurae fall together, preventing the formation of a cavity. This touching of the pleurae takes place mainly along the anterior and lower borders. During quiet respiration the costal and the diaphragmatic pleurae remain in apposition below the lower border of the lung. The space thus formed is known as the costodiaphragmatic recess. It is about 2 inches deep behind, 3 inches deep in the midaxillary line and a little over 1 inch deep in front.
SURFACE MARKINGS The surface markings of the lungs and the pleurae are of diagnostic value and can be constructed in the following way: The junction of the costal and the mediastinal pleurae (costomediastinal line of pleural reflection) is not the same on both sides of the body. On the right, it starts about 1 1/2 inches above the sternoclavicular joint and passes to the middle of the manubrium opposite the 2nd costal cartilage. From this point it drops vertically near the midline of the sternum to the xiphosternal joint, where it becomes continuous with the costodiaphragmatic line of reflection. On the left side, the line of pleural reflection is the same until the 4th interspace. Here it curves outward to the left border of the sternum along which it descends to the xiphosternal junction. It becomes continuous with the costodiaphragmatic line of reflection just as it does on the opposite side. The junction of the costal and the diaphragmatic pleurae (costodiaphragmatic line of pleural reflection) may be marked by a line which starts at the xiphosternal joint and passes posteriorly to the 12th thoracic vertebra, the line being convex downward.
FIG. The pleural cavities and the pleurae. (A) Diagrammatic presentation showing an early stage of development and the end result. The lung invades the pleural cavity so completely that only a potential pleural space remains. The process divides the pleura into visceral and parietal portions. (B) Side view seen from the left. The lung has been removed, and a window cut in the costal pleura. The 4 parts of the parietal pleura are identified, as are the pulmonary root and ligament. (C) The sternal and vertebral reflections.
It crosses the 10th rib in the midaxillary line, lies about 2 inches above the costal margin and marks the lowest level of the pleural sac (not lung). It ascends slightly after passing this point and terminates opposite the 12th thoracic vertebra.
Lungs. The lungs may also be marked on the surface of the body. The apices lie about Vi inch above the inner third of the clavicles, then descend behind the sternoclavicular joints toward the midline of the sternum (level of the 2nd rib). At this point the lungs almost touch each other. The anterior border of the right lung follows the line of its pleura
FIG. The surface markings of the lungs and the pleurae: (A) anterior view, (B) left lateral view, (C) right lateral view, (D) posterior view.
directly downward to the 6th costal cartilage. The anterior border of the left lung descends as far as the 4th costal cartilage where it curves to the left, exposing an area of pericardium called the area of cardiac dullness. This curving line ends opposite the 6th costal cartilage about 1 Vi inches from the midline; the summit of this space is in the 4th interspace about 2 inches from the midline. The lower borders of the lungs are practically at the same level on both sides; they lie at a higher level (about 3 inches) than their corresponding pleural sacs (the costodiaphragmatic line). The lower border of each lung can be marked by a line which passes laterally behind the 7th rib in the midclavicular line, and the 8th rib in the midaxillary line; the latter is its lowest level. From here it terminates posteriorly opposite the 10th thoracic spine.
SURGICAL CONSIDERATIONS
FRACTURED RIBS The ribs which are usually fractured are the 3rd to the 8th; ribs 1 and 2 and those below the 8th are infrequently involved. The fracture of the bone proper is of no great importance with the exception of the local discomfort which it produces. However, complications such as puncture of the pleura, the lung, the liver or the spleen, as well as diaphragmatic hernia, secondary pleural effusion and surgical emphysema may result in serious sequelae. Little displacement or shortening occurs in rib fractures because of the attachment of the intercostal muscles and fixation of both rib extremities.
ASPIRATION OF THE CHEST The chest is aspirated as either a diagnostic or a therapeutic procedure. It is performed best with the patient seated and with the arm of the involved side placed on the opposite shoulder. If this is impossible, the aspiration may be done with the patient lying on the uninvolved side. The site of election is usually a little posterior to the posterior axillary line in the 6th, the 7th or 8th intercostal space. Some prefer the midaxillary line. The needle should be passed a
FIG. Fractured ribs and their complications. The sharp end of a broken rib may injure the pleura, the lung, the liver, the spleen or the diaphragm.
little toward the superior surface of the lower rib so that the intercostal artery and nerve are not injured.
THORACOSTOMY Thoracostomy is an opening made through, the chest wall for the purpose of drainage.It may be a closed (interspace) or an open (rib resection) drainage. The indication for such drainage is usually empyema.
Closed Method. This is usually made in the 7th or 8th interspace in the midaxillary line or in line with the angle of the scapula. Procaine is injected at the selected site, and
FIG. Aspiration of the chest. (A) Diagrammatic presentation of the relation between the aspirating needle and the fluid level. (B) Aspiration in the midaxillary line.
a small stab incision is made. A trocar is inserted just over the rib, thus avoiding the intercostal artery, vein and nerve which lie on the undersurface of the rib. This is advanced into the pleural space where the fluid is located. The obturator is withdrawn, and a catheter is inserted. Then the trocar is drawn over the catheter, which fits snugly and may be fixed by pins or a suture.
Open Method (Rib Resection) and Thoracoplasty. This method necessitates the resection of a piece of rib. The angle of the scapula is palpated, and then the patient’s arm is elevated and placed to the opposite side. The rib immediately below this point is usually selected as the one suitable for resection. If the rib above is chosen, the scapula may act as a shutter; if a rib much lower is selected, an inadvertent transthoracic laparotomy may be performed. An incision is made directly over the rib selected, the soft tissues are divided to the periosteum, which is completely freed, and about 2 to 4 cm. of rib is removed. The pleural cavity is aspirated to make sure that pus is present. The aspirating needle may be left in place, and an incision is made adjacent to it. The cavity is explored, and then drainage is instituted. In chronic, nontuberculous empyema the lung is compressed by intrapleural fluid. At times a draining sinus results. Radical surgical intervention is necessary. Even after evacuation of the pus, expansion of the lung is not possible, and a pleural dead space results which is difficult to obliterate. Two rocedures have been advised which aim at approximating the lung surface and the chest wall, thus eliminating the dead space. The
FIG. Closed (interspace) thoracostomy.
first is pulmonary decortication, in which one attempts to mobilize the lung. If this is sufficiently accomplished, the lung gradually expands and fills the pleural cavity. The other procedure is thoracoplasty, which consists of subperiosteal removal of usually 6 ribs to permit the chest wall to fall in and meet the collapsed lung. This may be accomplished by either a posterior or an anterolateral approach. Another method which has been utilized to obliterate such a cavity is the use of a muscle flap.
FIG. Thoracoplasty. (A) and (B) show the posterior approach; (1) and (2) demonstrate the anterolateral approach. The cross section shows the effect of this procedure, which permits the chest wall to fall in and meet the collapsed lung.
Lungs (Pulmones)
EMBRYOLOGY Embryologically, the pulmonary system arises as an outgrowth of the digestive tract. It begins as a small bud which grows from the ventral part of the pharynx. The bud increases in length to form the trachea, which in turn divides into right and the left primary bronchi. The ends of these bronchi continue to grow and divide until eventually a complex bronchial tree with the terminal alveoli is formed. At first, the pleural cavity is in direct communicationwith the abdominal cavity, the two together forming the celom. Later, these are separated by a transverse partition, the diaphragm.
THE LUNGS PROPER The lungs are a pair of comparatively light organs which are conical in shape, each of which possesses an apex, a base, 2 surfaces, 3 borders (anterior, inferior and posterior) and a root. Although they lie within the pleural cavities, they do not fill all the available space during normal respiration. The weights of the ordinary, healthy adult lungs, containing the average amount of blood, are about 620 grams for the right lung and about 570 grams for the left. If the lungs are in a healthy state, they lie free in the pleural cavity and are attached at only 2 points: at their roots and at the pulmonary ligaments. However, healthy lungs are rarely found in dissecting rooms, since adhesions due to
pleurisy are usually present between the visceral and the parietal layers of pleura. The 2 lungs are not exactly symmetrical in shape because of the higher level of the diaphragm on the right, the projection of the heart to the left of the midline, and the impressions made by surrounding structures. At birth, the lungs are pinkish white, in adult life dark gray, and as age advances the mottling assumes a black color, due to carbonaceous deposits. As a rule the posterior border is darker than the anterior. Apex. The apex of the lung is examined in the lower part of the neck because of the obliquity of the thoracic inlet. It is rounded and rises into the root of the neck for about 1 1/2 inches above the level of the anterior part of the 1st rib. It is situated behind and above the medial third of the clavicle and is crossed by the subclavian artery, which makes a groove on its anterior border slightly below its summit. The lung is separated from the artery by the pleura and a thin membrane known as Sibson’s fascia. The summit of the apex is in front of the neck of the 1st rib. The lung apex lies behind the clavicle, the anterior scalene muscle, the subclavian vessels and Sibson’s fascia, which is attached along the inner border of the 1st rib and strengthens the pleura over the apex. The pleura in this region may be opened inadvertently during surgery near the subclavian vessels and also can be torn while removing deep-seated tumors from the depth of the neck. The pleura and the lungs may be injured in stab wounds of the neck or by fragments of bone in comminuted fractures of the clavicle.
Base. The base (diaphragmatic surface) is concave. The diaphragm separates it on the right side from the liver and on the left from the stomach, the liver and the spleen. Because the right dome of the diaphragm is higher and more convex than the left, the right lung is shorter, and its base is more concave. Laterally and behind, the base is
FIG. The apex of the lung. This is associated with the root of the neck. The inset shows the subclavian artery crossing the apex.
bounded by a thin sharp margin which projects into the phrenocostal sinus of the pleura between the lower ribs and the costal attachments of the diaphragm.
SURFACES The two surfaces of the lungs are the costal surface and the medial (mediastinal). The costal surface is smooth, convex and includes the bulky posterior part of the lung. It is related to the inner surfaces of the ribs, the costal cartilages, the intercostal spaces and, to a slight degree, the back of the sternum.
FIG. The medial surface of the right lung. (A) Grooves and impressions made by structures in immediate contact with this surface, viewed from the left. (B) The lungs and the heart, seen from in front.
The medial surface of each lung is divided into anterior (mediastinal) and posterior (vertebral) parts. Both parts present different relationships on the 2 sides of the body and must be considered separately. On the right side, the hilum is occupied by the eparterial and the hyparterial bronchi, the right pulmonary artery and the upper and the lower right pulmonary veins. In the hilum, numerous lymph glands and nerves are also found. Below and in front of it, the mediastinal part presents a cardiac impression which is formed by the right atrium and a groove for the phrenic nerve. The superior vena cava is in contact with the right lung in front of the hilum, and the impression made by this vessel is continuous with the groove made by the right innominate vein above and the cardiac impression below. Above the hilum a groove is sometimes visible which runs into the groove for the superior vena cava; it is produced by the vena azygos. The groove produced by the esophagus is found immediately behind this. The vertebral part of the medial surface of the right lung is in relation to the heads of the ribs, the sympathetic trunk, the vertebral bodies, the splanchnic nerve and the aortic intercostal arteries and veins. On the left side, the hilum reveals a single left bronchus, the left pulmonary artery, upper and lower left pulmonary veins, numerous lymph glands and nerves. The ventricles of the heart produce a deep cardiac impression below and in front of the hilum. The arch of the aorta passes backward above the root of the lung and is continuous behind the hilum, along with the groove produced by the descending thoracicaorta. Above the groove for the aortic arch, the subclavian artery passes upward in contact with the lung and then turns laterally in front of the apex. The vertebral part of the medial surface of the left lung is grooved by the descending thoracic aorta which separates the lung from the bodies between the 4th to the 9th thoracic vertebrae. Other relationships in this area are the same as those described for the right lung. BORDERS The 3 borders of the lungs are the anterior, the inferior and the posterior. The anterior borders of the lungs are thin and sharp because they are squeezed between the body of the sternum and the pericardium. On the right side the border is straight and coincides with the costomediastinal line of pleural reflection. On the left side, however, the anterior border presents a deep notch opposite the 4th and the 5th intercostals spaces known as the cardiac notch. Here the border of the lung falls short of the sternum by about an inch, leaving part of the pericardium separated from the chest wall by pleura alone. This area which is unoccupied by lung has been referred to as the “area of superficial cardiac dullness.” The inferior border separates the base of the lung from the costal and the medial surfaces. Laterally and behind, it is sharp and projects down to the upper part of the costodiaphragmatic recess. The inferior borders of both lungs are practically at the same level, and during quiet respiration they lie at a higher level than the costodiaphragmatic line of pleural reflection. The posterior border is indistinct and rounded, due to the confluence of the medial and the costal surfaces which occupy the deep hollow of the thoracic cavity. It projects into the phrenocostal sinus.
FISSURES, LOBES, AND BRONCHOPULMONARY SEGMENTS
Oblique Fissure. Each lung presents a complete oblique fissure which passes through the costal, the diaphragmatic and the mediastinal surfaces as far as the root. This fissure crosses the posterior border about 2 1/2 inches below the apex and the inferior border about 2 inches from the median plane. Transverse Fissure. The right lung reveals a second fissure known as the transverse fissure. It runs horizontally at the level of the 4th costal cartilage and meets the oblique fissure in the midaxillary line. The left lung, therefore, is divided into two lobes, a superior and inferior, by the interlobar fissure (oblique); the right is divided into three lobes, superior, middle and inferior, by the two (oblique and transverse) interlobar fissures. The superior (upper) lobe lies above and in front of the oblique fissure and includes the apex, anterior border, a large part of the costal surface and the greater part of the mediastinal surface of the lung.The inferior (lower) lobe is the larger of the two, and is situated below and behind the fissure. It includes almost all of the base, a large part of the costal surface, and the greater part of the posterior border. Middle Lobe. In the right lung the middle lobe is the smallest. It is wedge-shaped and includes the lower part of the anterior border and the anterior part of the base of the lung. It lies in the front part of the thorax and is entirely anterior to the midaxillary line.
FIG. Lobes and fissures of the lungs. (A) Front view; the usual arrangement of 3 lobes on the right and 2 lobes on the left is shown. (B) The right lung seen from the right side. (C) The left lung seen from the left side. (D) The 2 accessory lobes which may be found associated with the right lung. The infracardiac lobe is constant in quadrupeds, but in man the pericardium fuses with the diaphragm and suppresses its development. The lobe of the azygos vein (Wrisberg) is also shown.
The cardiac notch is formed by a deficiency of the upper lobe of the left lung. Bronchopulmonary Segments. The lobes are subdivided into smaller units called bronchopulmonary segments which may be defined as the area of distribution of a bronchus. The various descriptions of the anatomy of the tracheobronchial tree have
FIG. Nomenclature for the lungs and the bronchi (After Jackson and Huber). The numbers in parentheses relate to the numbers on the illustration. The lobes are divided into smaller units called bronchopulmonary segments, each of which is determined by the area of distribution of a bronchus. The right lung presents 3 lobes; upper, middle and lower. The upper has been colored blue, the middle yellow and the lower red. The upper lobe has 3 segments: (1) apical, (2) posterior and (3) anterior. The middle lobe has 2 segments: lateral (4) and medial (5). The lower lobe consists of 5 segments: superior (6), medial basal (7), anterior basal (8), lateral basal (9) and posterior basal (10). The left lung is divided into 2 lobes: an upper, colored blue, and a lower, colored red. The upper lobe is divided into 2 divisions: upper and lower (lingular). The upper division has 2 bronchopulmonary segments: they are known as the apical, which is also called the apical posterior (1 and 2) and an anterior (3). The lingular division also has 2 segments: superior (4) and inferior (5). The left lower lobe segments are similar to those on the right except that the medial basal is a branch of the anterior basal rather than a separate branch of the lower lobe bronchus. The term “anterior-medial basal” (7 and 8) is used to call attention to this fact. The other numerical representations are the same as those of the right side. The colors and the numbers which have been used on the bronchi correspond to the colors and the numbers of the individual bronchopulmonary segments.
resulted in much confusion; hence, we have chosen the nomenclature used by Jackson and Huber which seems to be acceptable to the surgeon, the bronchoscopist, the radiologist and the anatomist. It may be listed as shown at the bottom of the page: At times, 2 branches which generally constitute separate major segmental bronchi may have a common trunk. This would explain the variation in descriptions of the right upper lobe which is described as having 4 segments by some and by others as having only 3. Since fissures may be quite inconstant, it is far better to subdivide the lungs according to bronchial distribution. The right lung usually presents 3 lobes: upper, middle and lower. The upper lobe consists of 3 segments: apical, posterior and anterior. The middle lobe has 2 segments: lateral and medial. The lower lobe has 5 segments which are known as the superior, the medial basal, the anterior basal, the lateral basal and the posterior basal. The left lung usually consists of 2 lobes: upper and lower. Moreover, the upper lobe has 2 subdivisions which are known as the upper and the lower divisions. The lower division of the upper lobe is also called the lingular division. Two segments make up the upper division; these are known as the apical (apical-posterior) and the anterior. The lingular division is made up of 2 segments: superior and inferior. In the left lower lobe the segments are similar to those on the right, except that the medial basal is a branch of the anterior basal rather than a separate branch of the lower lobe bronchus. It has been suggested that the term anterior-medial basal be used to call attention to this fact.
VARIATIONS Variations are found in the number of lobes of the lungs which may be either decreased or increased. The right upper and middle lobes may be fused, and the left lung may have 1 or even 3 lobes. The right lung sometimes has 5, since 2 accessory lobes may be associated with the 3 usual ones.
Infracardiac Lobe. One such accessory lobe is the infracardiac lobe, which is constant in quadrupeds; in these animals it separates the pericardium from the diaphragm. In man, since the pericardium fuses with the diaphragm, the infracardiac lobe is completely suppressed.
Lobe of the Azygos Vein. The most important accessory lobe is the so-called lobe of the azygos vein (Wrisberg). The azygos vein travels upward in front of the vertebral column, arches forward above the root of the lung and ends in the superior vena cava before the latter pierces the pericardium. Therefore, the arch of the azygos vein crosses laterally in respect to the esophagus, the trachea and the right vagus nerve. During development, the right lung bud has to pass outward under the arch formed by the anterior end of the future azygos vein (right posterior cardinal vein). If the lung bud does not clear it, part of the lung remains lateral and part medial to it. Therefore, the vein becomes embedded in the developing lung tissue, and
RIGHT LUNG
LOBES & SEGMENTS
Upper [Apical. Posterior. Anterior.] Middle [Lateral. Medial.] Lower [
LEFT LUNG
LOBES & SEGMENTS
Upper (Upper Division ) [Apical-posterior & Anterior ]
(Lower Lingular Division ) [Superior & Inferior ]
Lower [
the part medial to it becomes the lobe of the azygos vein. This condition was first described by Wrisberg in 1717. When the apex of the right lung is split by the arch of the azygos vein, a bifid apex results. The vein is suspended by a pleural “mesentery” which is referred to as a double pleural septum or “meso-azygos.” If this is seen on the roentgenogram, the meso-azygos appears as a fine line running from the apex of the lung downward with the convexity outward as it approaches the mediastinum at about the level of the 2nd costal cartilage. This line ends in a small, dense, pea-sized shadow, which represents the azygos vein. Such an accessory lobe is important to identify, since it might cause confusion in the interpretation of a roentgenogram, in pulmonary surgery, or during post-mortem examinations. It may form the entire apex of the lung, part of it, or may be entirely disassociated from it, depending on the location of the vein.
ROOT OF THE LUNG (RADIX PULMONIS)
The root of the lung is a short but broad pedicle consisting of 3 essential structures, the pulmonary artery, pulmonary veins and bronchi. Associated with these are the bronchial vessels, nerves and lymph glands.
Pulmonary Ligament. This ligament is also considered with the root. Although there are some differences in the right and the left roots, it is well to remember that the bronchi lie posterior to the vessels, and the pulmonary veins usually lie below the corresponding right or left pulmonary arteries. Many anomalies in this region have been recorded. The right root has the following boundaries: anteriorly, the superior vena cava and the phrenic nerve; superiorly, the arch of the azygos vein; posteriorly, the azygos vein proper. The left root is bounded in the following way: anteriorly, by the phrenic nerve; superiorly, by the aortic arch; posteriorly, by the descending thoracic aorta. It might help to recall that on the right side, an inverted “U” is formed by the phrenic nerve and the azygos vein, while on the left side, a similar inverted “U” is formed by the phrenic nerve and aorta. The structures of each root are bound together by connective tissue and pleura which surround them like a cuff.
BLOOD VESSELS Much has been written about the variations of the bronchovascular patterns (Boyden et al.) and the variations of the origin, the course and the distribution of the bron-
FIG. Pneumonectomy (right side). (A) Anterior approach through a transverse incision over the 3rd intercostal space. (B) Exposure of hilar structures by incising the mediastinal pleura anteriorly and superiorly. (C) Ligation and division of the azygos vein (D) Ligation and division of hilar structures followed by removal of the lung (E) Pleuralization.
chial arteries (Cauldwell et al.). Such works may be consulted for detailed study; however, the following description presents the most commonly accepted basic concepts.
The pulmonary veins, usually 2 on each side consisting of an upper and a lower, return oxygenated blood to the heart. Two main venous trunks from each lung open into the left atrium on its lateral border.
The pulmonary artery, after leaving the right ventricle, passes superiorly for about4 cm. and a little to the left of the ascending aorta. The right branch goes to the right lung behind the aorta, and the left branch to the left lung in the concavity of the aortic arch. In the lung pedicle, the right divides into 2 branches, and the left remains single. These vessels end in a capillary network over the alveolar tissues carrying the impure venous blood from the right ventricle to the lung. A thrombus of the right side of the heart of systemic venous origin can release an embolism which blocks a branch of the pulmonary artery, causing a suppression of part of the lung. A pulmonary infarct may result which might degenerate and become a pulmonary abscess.
The bronchi are easily identified by the film, elastic, fibrocartilaginous plates. On the right side there is an additional bronchus
which receives the name of the eparterial bronchus, because it is at a higher level than the artery. This is in contradistinction to the hyparterial bronchi which are found on both sides below the pulmonary artery. The cuff or sleeve of pleura which surrounds these structures is quite narrow in its inferior or lower portion because it is traversed only by a few lymph vessels and, therefore, remains collapsed; its anterior and posterior walls are applied to each other and form the pulmonary ligament.
The bronchial arteries which supply the lung stroma are found on the posterior surfaces of the bronchi; they arise from the aorta or from an intercostal artery and pass behind the bronchi. Bronchial veins accompany them.
SURGICAL CONSIDERATIONS
PNEUMONECTOMY Nissen, Overholt, Rienhoff, Graham and Alton Ochsner have pioneered in pneumonectomy and have shown the advisability of performing this operation for primary pulmonary malignancies. Several types of incisions may be employed, the choice depending upon the presence or the absence of adhesions, and the location of the pathology. Some surgeons think that anatomic planes exist in the pulmonary hilus, and they state that a venous plane is found more superficially than an arterial plane or a bronchial plane. However, there are so many variations in the hilar structures that the method is not practical, especially since the inferior pulmonary vein may often be the most posterior structure. The anterior approach usually consists of a transverse incision over the 3rd intercostals space extending from the lateral border of the sternum to the anterior axillary line . The pectoral muscles are divided and the pleural cavity entered through the third intercostal space. Greater exposure can be gained by separating the 3rd and 4th ribs after disarticulating their costochondral junctions, and by ligating the internal mammary vessels both above and below. The pleural cavity is opened, and adhesions are divided by sharp dissection. The hilar structures are exposed in the mediastinum by incising the mediastinal pleura, anteriorly and superiorly. The phrenic nerve may be crushed by an artery forceps. This facilitates surgery and also aids the early postoperative course. It is important to isolate and ligate the hilar structures individually and not by mass ligations. On the right side, the isolation, the ligation and the division of the azygos vein is the first structure to be dealt with; it extends over the right main bronchus. Then the pulmonary artery is isolated, doubly ligated and divided. The bronchus is usually ligated next, but it may be necessary to isolate, transfix, ligate and divide the superior pulmonary vein first. Then the bronchus is freed, ligated and divided; usually it is closed by interrupted sutures. The short inferior pulmonary vein is next found, transfixed, ligated and severed. The posterior mediastinal pleura is then incised, and the lung is removed. The edges of the divided mediastinal pleura are approximated, covering the stumps of the ligated hilar structures. When a large amount of mediastinal pleura has been extirpated, it might be necessary to utilize the adjacent pericardium to cover the ligated stump. The thoracic wall is closed in layers by passing heavy nonabsorbable sutures around the adjacent ribs. Following this, the pleura and the intercostal muscles are approximated, either with or without drainage. A posterolateral approach is preferred by some surgeons
LOBECTOMY AND PULMONARY SEGMENTAL RESECTION
Both of these procedures have been used for such conditions as bronchiectasis, pulmonary tuberculosis, chronic lung abscesses and metastatic lesions. Clagett and Deterling have described a technic of lingulectomy in bronchiectasis. Churchill and Belsey, and Overholt and Langer have stressed the importance of pulmonary segmental resection. They state that bronchiectasis is a segmental disease and rarely involves an entire lobe. Nelson stressed the point that each bronchopulmonary segment possesses an independent bronchovascular structure and is separated from adjacent pulmonary tissue by an avascular cleavage plane. Therefore, segmental resectioot only eradicates all of the diseased tissue, butalso spares the uninvolved segment.
LUNG ABSCESS A nontuberculous lung abscess is a circumscribed pyogenic infection of the lung. It is usually associated with a history of tonsillectomy or aspiration of a foreign body such as teeth, peanuts, etc. Fusiform bacilli, Vincent’s spirochetes and streptococci may be aspirated with the foreign body or blood. The right lower lobe is most commonly involved. Treatment may be instituted in one of 3 ways: intercostal drainage, costectomy with drainage, or a 2-stage operation. Intercostal drainage is accomplished by means of an incision made parallel with the overlying muscle fibers which are separated and retracted. The incision is extended through the intercostal muscles and to the parietal pleura. Evidence of motion of the lung is noted. If the pleura is thickened, and if normal gliding movements of the lung cannot be seen, one concludes that the visceral and parietal pleurae have become adherent by adhesions, and opening of the abscess is safe. If adhesions have not been formed between the pleural surfaces, the operation is interrupted, and the wound is packed with gauze to promote the formation of adhesions. After a week or 10 days, pleural adhesions are usually present in sufficient amount to protect the pleural cavity from contamination, and then the abscess opened. An aspirating needle usually locates the abscess first, and when pus is found, the needle is followed with a scalpel or a cautery into the abscess cavity. Then drainage is instituted.
Costectomy with drainage is usually the operation of choice, since it provides adequate drainage. The abscess is located by several roentgenograms, and the skin incision is placed as close to the pathology as possible. A section of rib is resected, usually from 5 to 8 cm. long, which overlies the abscess. The pleura is exposed, and if the pleurae are adherent, the abscess is entered; if not, a 2-stage operation is performed. The 2-stage operation with rib resection is considered by many to be a safer procedure. The periosteum is stripped from 2 or 3 ribs for a distance of 8 or 10 cm. The middleone of these 3 ribs is resected. The periosteum is raised from the 2 adjacent ribs which will be resected later. Gauze is packed beneath the denuded rib to form adhesions between the visceral and the parietal pleurae. At the end of 7 to 10 days, the wound is reopened; the abscess is located with a needle and entered. Then drainage is instituted.
Trachea and Extrapulmonary Bronchi
THE TRACHEA PROPER The trachea begins where the larynx ends, that is, at the lower border of the cricoid cartilage which is on a level with the 7th cervical vertebra. It is from 4 to 5 inches long, half of which is in the neck (cervical portion), and the other half in the thorax (thoracic portion). The trachea enters the thoracic inlet opposite the upper border of the manubrium sterni and ends at its lower border; the latter point is situated on a level between the 3rd and the 4th thoracic spines, where it divides into right and left primary bronchi. Its thoracic portion is opposite the manubrium and wholly within the superior mediastinum. It occupies the median plane except at its lower end where the aortic arch pushes it slightly to the right. About 15 or 20 horseshoeshaped rings of hyaline cartilage keep its lumen open and support the lateral and anterior aspects, but they are deficient posteriorly where the wall is flattened. The posterior portion is closed by the trachealis muscle, which is made up of transverse plain fibers supplied by the recurrent laryngeal nerve. Anteriorly, the trachea is crossed by the isthmus of the thyroid (2nd to 4th ring), and below that structure it is related to the inferior thyroid veins which pass downward upon it, frequently communicating with each other and opening into the innominate veins. In young children, the left innominate vein may appear above the levelof the manubrium sterni, forming an anterior relation of the trachea.
RELATIONS Posteriorly, the trachea is in contact with the esophagus. Anteriorly, in the neck, the isthmus of the thyroid gland covers the 2nd, the 3rd and the 4th tracheal rings. In its lower part, it is crossed by the arch of the aorta, with the deep cardiac plexus intervening. Also in front of the trachea are the roots of the innominate and the left common carotid arteries which separate it from the left innominate vein. As these 2 arteries travel upward they diverge, and in the interval which is made by this divergence, the remains of the thymus gland are found. More anteriorly, the manubrium sterni is situated with the lower part of the sternohyoid and the sternothyroid muscles which arise from the back of it. On the right side, the trachea is in relation to the right pleura and lung, the right vagus nerve and the arch of the azygos vein. In the neck, it is related to the right lobe of the thyroid gland from the commencement of the trachea to the 6th ring. The right recurrent laryngeal nerve passes along its lateral posterior aspect. On the left side, it is related to the left common carotid and the subclavian arteries, the phrenic and the vagus nerves, and the lower part of the arch of the aorta where it is separated from the left pleura and lung. The left recurrent laryngeal nerve has the same relationship as the right. Many tracheobronchial lymph glands are associated with the trachea at its bifurcation: the paratracheal glands lie on each side of it in the superior mediastinum.
RIGHT AND LEFT EXTRAPULMONARY BRONCHI The bronchi diverge from each other on
FIG. The trachea and the extrapulmonary bronchi: (A) relations as seen from in front; (B) viewed from the left side; (C) the trachealis muscle seen in cross section.
their way to the roots of the lungs, and differ in size, length and the direction in which they run. The right bronchus is shorter, wider and more vertical. Because of this, foreign bodies from the trachea usually pass to the right side. It is about 1 inch long and, since it supplies the larger lung, is larger in size. Anterior to it are the right pulmonary artery, the pericardium, the lower part of the superior vena cava and the ascending aorta. The arch of the azygos vein is placed above, and the bronchial vessels and the posterior pulmonary plexus are posterior. The upper pulmonary vein is anterior; the lower pulmonary vein is below. The right bronchus gives off a branch which is called the eparterial branch, so named because it arises above the
FIG. The relations of the trachea and primary bronchi. The eparterial and the hyparterial branches of the right bronchus have been identified. A broncho-esophageal muscle was present in this specimen.
right pulmonary artery; it passes to the upper lobe of the right lung. The bronchus continues as the hyparterial branch which passes below the artery and divides into two, one branch for the middle lobe and one for the lower. The left bronchus has farther to travel than the right, since the left lung hilum is farther from the median plane. Therefore, it is nearly twice as long as the right and less vertical. The arch of the aorta passes backward and over it, and the descending thoracic aorta runs downward and behind it. Anteriorly, are the left pulmonary artery and the pericardium, which separate the bronchus from the left atrium. The posterior pulmonary plexus, the esophagus and the bronchial vessels are situated behind this bronchus. Occasionally, a muscle band exists between the esophagus and the left bronchus; this is called the broncho-esophageal muscle. The carina is a sagittal spur located at the margin of the primary bronchus. It is easily seen through the bronchoscope as it passes upward into the lumen. It is employed as a landmark by the bronchoscopist.
Mediastinum (Interpleural Space)
BOUNDARIES OF THE MEDIASTINA The mediastinum is the middle compartment of the chest which is situated between the 2 pleural cavities. Its boundaries are: anterior, the sternum; posterior,
FIG. 222. Diagrammatic sagittal section of the mediastinum. An imaginary line which extends from the sternal angle to the disk between the 4th and the 5th thoracic vertebrae divides the mediastinum into superior and inferior mediastina. The inferior mediastinum is divided by the heart into anterior, middle and posterior mediastina.
the bodies of the 12 thoracic vertebrae; superior, the thoracic inlet; inferior, the diaphragm. The sides are formed by the mediastinal pleurae. It is divided into superior and inferior mediastina by an imaginary line which extends from the sternal angle (manubriosternal joint) to the disk between the 4th and the 5th thoracic vertebrae. The inferior mediastinum is subdivided into 3 mediastina by the heart, which acts as the key structure in this subdivision. That part of the inferior mediastinum which contains the heart is called the middle mediastinum; that part in front of it makes up the anterior, and the part situated behind the heart constitutes the posterior mediastinum. Each of the 4 mediastina have their own boundaries.
CHIEF CONTENTS OF EACH MEDIASTINAL SPACE The superior mediastinum contains: the arch of the aorta and its 3 branches (innominate, left common carotid and left subclavian arteries); the innominate veins; the upper half of the superior vena cava; the vagus, the phrenic and the left recurrent nerves; the esophagus, the trachea and the thoracic duct; the thymus or its remains in the adult with some lymph glands. The anterior mediastinum contains a few lymph glands (anterior mediastinal glands) and a little areolar tissue. The middle mediastinum contains: the
FIG. Contents of the superior and the middle mediastina viewed from in front.
heart enclosed in the pericardium; the ascending aorta; the lower half of the superior vena cava (with the azygos vein entering it); the bifurcation of the trachea; the pulmonary artery dividing into right and left branches; the right and the left pulmonary veins; the phrenic nerves; the bronchial lymph glands. The posterior mediastinum contains: the esophagus; the descending thoracic aorta; the vagi; the thoracic duct; the azygos; the hemiazygos and the accessory hemiazygos veins.
FIG. Contents of the superior and the middle mediastina viewed from behind.
DRAINAGE OF MEDIASTINAL ABSCESS Most mediastinal abscesses (mediastinitis) are drained through a right supraclavicular incision which is made in a transverse direction. This is deepened between the thyroid gland and the trachea medially, and the carotid sheath and the sternocleidomastoid muscle laterally. A finger is in-
troduced along the right side of the esophagus and follows this downward until the abscess is reached and opened. Rarely is it necessary to perform an anterior or posterior mediastinotomy.
CARCINOMA OF THE ESOPHAGUS Carcinoma of the midthoracic esophagus has been treated quite successfully by Churchill, Garlock, Sweet and others. The lesion has been eradicated successfully by radical resection with high intrathoracic esophagogastrostomy. The essential steps in the operation are as follows: The usual incision is placed at the left costal margin anteriorly; it extends posteriorly over the 8th or the 9th rib and then curves upward for a short distance between the spine and the left scapula. The 8th or the 9th rib is resected. If greater exposure is necessary, the 5th, the 6th, or the 7th ribs are divided posteriorly. The left thoracic cavity is entered, the mediastinal pleura is incised, and dissection is begun anterior to the esophagus. Resectability depends on whether or not the growth has invaded the left main bronchus, the aortic arch or the inferior pulmonary vein. If these structures can be mobilized safely, dissection posterior to the esophagus is begun. The posterior dissection is left until last, to avoid interfering with the blood supply, resulting from the division of the esophageal arteries arising from the aorta. When the posterior dissection is completed, the tumor is freed from the right mediastinal pleura. The esophagus is mobilized from the aortic
FIG. Drainage of a mediastinal abscess: (A) right supraclavicular transverse incision; (B) the abscess is sought in a space between the trachea medially and the carotid sheath laterally.
FIGURE. (Facing page). Resection for carcinoma of the midthoracic portion of the esophagus. (A) The incision is placed at the left costal margin anteriorly, extends posteriorly over the 8th or the 9th rib and curves upward between the spine and the left scapula. (B) Anterior dissection of the esophagus. (C) The esophagus and the stomach have been mobilized and prepared for resection. (D) The anastomosis between the esophagus and the stomach is made high in the thoracic cavity. (E) To relieve tension on the anastomotic suture line, interrupted sutures fix the stomach to the parietal pleura and the diaphragm.
arch downward, and the abdomen is entered through an incision in the diaphragm which extends from the esophageal hiatus to the insertion at the costal margin. Phrenic nerve crushing immobilizes the diaphragm. The greater curvature of the stomach is mobilized by dividing the gastrolienal ligament and ligating the left gastroepiploic vessels and vasa brevia. The gastrocolic omentum is divided as far as the pylorus, but the right gastric and gastroepiploic vessels are protected. In the region of the lower esophagus and cardia, it may be necessary to ligate branches of the superior suprarenal, inferior phrenic and pericardiophrenic vessels. Next, the gastrohepatic ligament is severed and occasionally a hepatic branch of the right inferior phrenic artery is found in this structure. The left gastric vessels are ligated. The stomach is divided distal to the cardia, and the distal portion is inverted with sutures. An incision is made in the mediastinal pleura above the aortic arch, and the attachments of the esophagus behind the arch are freed. These are usually small vessels which arise from the aorta and the bronchial arteries. When the esophagus has been fully mobilized,it may be pulled up from behind the aortic arch and prepared for the anastomosis. The esophagus and the tumor are resected, and the anastomosis is completed. To relieve tension on the anastomotic suture line, interrupted sutures fix the stomach to the parietal pleura and the diaphragm, which is closed. The stomach now receives its blood supply from the right gastric and the right gastroepiploic arteries. If the anastomosis is placed below the aortic arch, an adequate blood supply to the esophagus is maintained by the small arteries from the aorta and the bronchial vessels. However, if it is necessary to dissect the esophagus above the aortic arch, the blood supply is entirely dependent on the descending branches from the inferior thyroid artery. The thoracic duct may be encountered or injured in these high dissections; it is important to ligate this structure to prevent a leakage of chyle. Ivor Lewis states that carcinoma in the middle third of the esophagus should be approached through a right transpleural route. His reasons for this are the following: This offers easier accessibility; only the vena azygos major requires ligating; and the aortic arch, instead of being an obstacle, becomes a safety barrier between the surgeon and the opposite pleural cavity. Therefore, he concludes that to operate on this part of the esophagus through the left side is unanatomic. His operation is usually performed in 2 stages. The first stage is done through an upper left paramedian incision, the abdomen being carefully explored. If there are no metastases on the greater curvature of the stomach, this structure is mobilized as has been described above. A jejunostomy is done to improve the patient’s nutrition. From to 15 days later, the second stage is accomplished by removing the right 6th rib and entering the chest. The vena azygos major is divided, and the procedure progresses much in the same way as has been described. Lewis claims that the cardia of the stomach can be delivered readily into the right thoracic cavity.
TRANSTHORACIC SUPRADIAPHRAGMATIC SECTION OF THE VAGUS NERVES (VAGECTOMY, VAGOTOMY) Dragstedt and others have advocated this procedure as a therapeutic measure for duodenal ulcers in the absence of pyloric stenosis, gastrojejunal ulcers and gastric ulcers where the diagnosis is certain. The incision is placed over the 8th rib on the left side, and the rib is resected widely.
FIG. Transthoracic vagus nerve section (vagotomy). (A) Incision over the left 8th rib. (B) Removal of a section of the left 8th rib. (C) Mobilization of the esophagus and exposure of the vagus nerves. A communicating nerve branch which is quite constant is noted in this subject. (D) The esophageal triangle. The esophagus can be found readily in a triangle bounded in front by the heart, behind by the descending aorta and below by the diaphragm.
Greater exposure may require the additional removal or fracture of adjacent ribs. The left pleural cavity is entered through the rib bed, and the collapsed lung is retracted upward. The inferior pulmonary ligament is identified and severed. The lower end of the esophagus will be found in an anatomic triangle which is bounded in front by the heart, behind by the descending aorta and below by the diaphragm. Cutting the inferior pulmonary ligament exposes this triangle and the esophagus. The vagus nerves are identified by palpation, since they have no elastic fibers and feel like taut cords. In most cases, they appear as 2 main trunks, but recent work on vagal anatomy reveals that considerable variation in the arrangement of the nerves takes place. The left vagus appears anterior to the esophagus and extends to the lesser curvature of the stomach. The right vagus is situated posteriorly. A large communicating branch between the vagi is a rather constant finding. Additional small fibers may be found on the esophagus. All the nerves and fibers are severed, and the large ones are ligated. The esophagus is returned to its bed, and the pleura is closed.
Pericardium
PERICARDIAL SAC The pericardium is a fibroserous sac which is located in the middle mediastinum and encloses the heart and the roots of the great vessels. It has the appearance of a truncated cone with its base resting on and fused with the central portion of the diaphragm. Its blunt apex reaches the level of the second costal cartilage. The outlineof the pericardium corresponds to that of the heart except that it reaches the 2nd costal cartilage on both sides, whereas the heart extends only to the 3rd cartilage on the right.
PERICARDIAL LAYERS The pericardium has 3 layers so arranged that the fibrous pericardium is entirely parietal, but the serous has both visceral and parietal layers.
FIBROUS PERICARDIUM The fibrous pericardium is applied to and is firmly fused with the outer surface of the parietal layer of serous pericardium. It is a sheet of considerable strength which fuses with the central tendon of the diaphragm interiorly and can be separated from it only by sharp dissection. Superiorly and posteriorly, it blends with the outer coats of the great vessels as they enter or leave the pericardial sac. It is by means of the outer fibrous coat of the arch of the aorta that the fibrous pericardium blends with the pretracheal layer of deep cervical fascia. Relations. The fibrous pericardium lies behind the body of the sternum and the costal cartilages from the 2nd to the 6th inclusive. Its anterior surface is separated from these structures-by the lungs and the pleura except at 2 places. One point of contact is in the median plane, where the fibrous sac is attached to the upper and the lower parts of the body of the sternum. This is brought about by two condensations of mediastinal areolar tissue which are called the upper and the lower sternopericardial ligaments; these are of clinical importance in adhesive pericarditis. The other point of contact is in the region of the bare area of the pericardium, which has no covering of lung. This is located at the sternal end of the left 5th costal cartilage. Here the cardiac notch leaves a deficient area of left pleura, and the pericardium comes in direct relation to the left sternocostalis muscle and the sternum. This area is of importance to the surgeon, since he may tap the pericardial sac at this point without injury to the pleura. Both side walls of the pericardium are in relation to the mediastinal pleura.
VISCERAL AND PARIETAL LAYERS The visceral layer of serous pericardium is usually called the epicardium. It is exceedingly thin and is so closely adherent to the outer surface of the heart that any attempt to detach it results in injury to the superficial layers of cardiac musculature. However, over the right side and the anterior surface of the ventricular portion of the heart, a certain amount of fat, even in thin individuals, occurs between the muscular tissues and the epicardium. The visceral layer covers the anterior and inferior surfaces of the heart and ascends on the back of the left atrium, where it is reflected downward as the parietal layer of serous pericardium. This reflection forms the upper limit of a cul-de-sac, known as the oblique sinus of the pericardium. The parietal layer follows and adheres to the fibrous pericardium. The pericardial sac can be marked on the surface of the thorax as extending from the 2nd costal cartilage above to the 6th below. On the right, it extends for Vi inch beyond the right margin of the sternum, and to the left it forms a line which passes upward and medial from the cardiac apex to the 2nd left costal cartilage about 1 1/2 inches from the midline. The latter is convex upward and to the left. When the anterior wall of the pericardium is opened, it is noticed that its outer wall appears to be fibrous (fibrous pericardium), but its inner wall is lined with a thin, glisten-
FIG. The pericardium. This fibroserous sac encloses the heart and the roots of
the great vessels. The pericardium has been cut open to reveal these structures.
ing serous membrane (parietal layer of serous pericardium). The parietal and the visceral layers of pericardium are continuous with each other anteriorly where the great arteries leave the heart, and posteriorly where the great veins enter it. That space which exists between the 2 layers of serous pericardium is a potential cavity called the pericardial cavity. It contains sufficient serous fluid to minimize friction between its 2 surfaces during heart action.
SURGICAL CONSIDERATIONS PERICARDIOCENTESIS
Aspiration of the pericardial cavity is done for diagnostic purposes or to release pressure in the pericardial cavity. Even with large effusions, the heart remains anterior and may be injured during this procedure. The aspirating needle should be placed to the left of the xiphoid, thus avoiding the internal mammary artery. Then it should be directed upward, backward and to the left, so that the heart is avoided and the left lateral pouch of dilated pericardium entered. If the needle is passed straight back, the left coronary artery may be injured.
PERICARDIOSTOMY (PERTCARDIOTOMY) C. S. Beck and others have emphasized the importance of the subatmospheric pressure which exists in the mediastinum. When the pericardium is opened, this is raised to atmospheric pressure, and the resultant compression on the heart causes a rise in venous pressure and a slight transient fall in arterial pressure. A normal heart may tolerate these changes, but should the heart be damaged, the patient might succumb. Many incisions and approaches for the purposes of draining the pericardial cavity have been described. One of the more common extends from the junction of the left 5th costal cartilage and sternum downward over the cartilages of the 5th, the 6th and the 7th ribs. About an inch of cartilage of the 5th, the 6th and the 7th ribs is removed, and the internal mammary vessels are ligated. The pericardium lies beneath, and the pleural space is to the left. An incision is made into the pericardium, and the fluid is aspirated from each lateral pericardial recess and from the oblique sinus. The pericardium is left open to drain. Soft rubber tubes are introduced into the opening; however, this is to be avoided in tuberculous pericarditis.
FIG. The pericardium seen from within and behind.
FIG. Pericardiocentesis
Heart
THE HEART PROPER With the pericardium opened, the heart presents a fixed posterosuperior portion—the atria (auricles); and a free antero-inferior portion—the ventricles. A groove containing fat, the auriculoventricular groove (coronary sulcus), marks the line of separation between atria and ventricles; it contains the right coronary artery. Passing downward and to the left, a similar groove is found which divides the ventricular portion of the heart, as seen in front, into a larger right and a smaller left ventricle. This groove corresponds to the attachments of the anterior margin of the septum between the right and the left ventricles and is known as the anterior interventricular groove (anterior longitudinal sulcus); it contains the anterior descending branch of the left coronary artery. All 4 chambers of the heart are visible from the “front” view; however, only a very small portion of the left atrium is visible: the auricle of the left atrium. The right border of the heart, which is convex, is formed by the right atrium; the left border is formed, almost entirely, by the left ventricle. The auricle of the left atrium aids in the formation of the left border at its uppermost part. Between the 2 auricles, the lower part of the pulmonary trunk covers the ascending aorta. That part of the right ventricle which is immediately below the pulmonary trunk is called the infundibulum. If the left index finger is passed in front of the superior vena cava, it can be directed from right to left behind the aorta and the pulmonary artery. The finger now lies in the transverse sinus of the pericardium. If the thumb is brought into contact with this index finger, the arterial end (aorta and pulmonary artery) of the heart lies between the 2 digits. All large vessels below the transverse pericardial sinus constitute veins (superior and inferior venae cavae and pulmonary veins). The sinus is bounded in front by the aorta and the pulmonary artery, and behind by the superior vena cava and the left atrium. It is possible to pass a finger through the sinus because the aorta and the pulmonary artery are enclosed in a complete sheath of visceral pericardium; the superior and the inferior venae cavae and the pulmonary veins are only partially covered (front and sides) by this layer. The transverse sinus connects the right and the left upper portions of the pericardial cavity. It is through this sinus that a rubber catheter is placed in the Trendelenburg operation for pulmonary embolus. If the fingers of the right hand are placed behind the apex of the heart and passed upward and to the right, they are stopped in a cul-de-sac of pericardium which lies behind the heart, between the left atrium and the pericardium. This is known as the oblique sinus of the pericardium. It is really an inverted “U” bounded below and on the right by the inferior vena cava and the right pulmonary veins, and above and on the left by the pulmonary veins. The sinus lies in front of the esophagus and the descending thoracic aorta. Fingers placed in the transverse and the oblique sinuses cannot touch each other because they are separated by 2 layers of serous pericardium surrounding the veins as they enter the left atrium.
SUPERIOR AND INFERIOR VENAE CAVAE The superior vena cava measures about 7 cm. in length and is formed by the junction of the 2 innominate veins, draining the blood from the upper half of the body. It begins immediately below the cartilage of the 2nd right rib, close to the sternum; it descends vertically behind the 1st and the 2nd intercostal spaces and
FIG. Heart and great vessels: (A) seen from in front
ends in the upper part of the right atrium opposite the upper border of the 3rd right costal cartilage. The lower half of the vessel lies within the pericardium and is devoid of valves at its orifice. The intrapericardial portion lies entirely within the fibrous pericardium and is covered in front and on either side by the serous pericardium which binds it to the fibrous layer. On its right side, it is separated from the right phrenic nerve and its companion vessels by the pericardium; on its left, and overlapping it slightly anteriorly, is the ascending aorta. Because of its close relationship to the ascending aorta, it may be compressed by aortic aneurysms. The transverse sinus intervenes between the superior vena cava and the ascending part of the aorta. In front of the vein, at its termination, is the right auricular appendix, and higher it is separated from the right lung and the pleura by the pericardial wall. Behind the vein is the fibrous pericardium which separates it from the root of the right lung. The vena azygos enters the back of the superior vena cava immediately before it pierces the fibrous pericardium.
The inferior vena cava is formed by the junction of the 2 common iliac veins on the right side of the 5th lumbar vertebra and returns the blood from
FIG. Transverse and oblique sinuses. (A) A catheter is placed in the transverse sinus. (B) The transverse sinus (in green) seen from above. The structures in front of the green line constitute the arterial flow of the heart (aorta and pulmonary artery); those behind the green line are veins (venae cavae and pulmonary veins).
the parts below the diaphragm to the heart. This vessel ascends along the front of the vertebral column to the right side of the aorta, passes in a groove on the posterior surface of the liver and then perforates the diaphragm between the median and the right portions of its central tendon. It pierces the fibrous pericardium, passes behind the serous pericardium and opens into the lower posterior part of the right atrium. Therefore, only a small part of this vessel, about % inch, is intrathoracic. Near its atrial orifice is a semilunar valve which has been called the valve of the inferior vena cava. This is usually rudimentary in the adult but may be large in the fetus, where it performs an important function. In the fetus this valve serves to direct the blood from the inferior vena cava through the foramen ovale into the left atrium. In its intrathoracic portion the following relationships are noticed: the diaphragm is in front of it; the vena azygos and the greater splanchnic nerve are behind it; the phrenic nerve, the right pleura and the lungs are lateral. The latter 2 structures also lie behind it.
COMPARTMENTS OF THE HEART
The compartments of the heart may be studied in the order in which they are traversed by the blood.
Right Atrium. If the heart is pulled to the left, a good view is obtained of the right side of the auricular portion and of the superior and the inferior venae cavae. The right atrium begins at the orifice of the inferior vena cava behind the 6th right cartilage. Immediately in front of the opening of the superior and the inferior venae cavae, an indistinct line might be seen which is called the sulcus terminalis. This line is of interest because it indicates the junction between the sinus venosus and the right auricle and marks a ridge which is on the inside of the right auricle called the crista terminalis. The sinus venosus is represented in the adult human heart by that part of the right auricle which lies behind the sulcus and receives the superior and the inferior venae cavae. If a window is cut in the right auricle, the crista terminalis is seen extending from the front of the orifice of the superior vena cava to the front of the orifice of the inferior vena cava. The atrium behind the crista is smooth, and in front it is trabeculated. The rugose appearance of the auricle in front of the crista is brought about by muscle bands which resemble the teeth of a comb; hence, the name musculi pectinati. The posterior wall of the atrium epresents the atrial septum, which separates the right atrium in front from the left behind. Near its center is noted a shallow oval depression, which is bounded by a thickened ridge every-
FIG. Right atrium and the right ventricle. Windows have been cut into these 2 heart chambers to show their internal structure. The arrow passes through the right atrioventricular orifice.
where except below. This depression is the fossa ovalis, and the ridge surrounding it is the annulus ovalis (limbus fossae ovalis). From the anterior horn of the annulus, there will usually be seen a crescentric membrane which passes forward and to the right, reaching the anterior wall of the auricle immediately in front of and to the right of the opening of the inferior vena cava. It is called the eustachian valve (valve of the inferior vena cava), which directed blood in the fetus from the inferior vena cava to the fossa ovalis, and was known as the foramen ovale. The tricuspid orifice (right atrioventricular orifice) occupies the lower portion of the anterior wall of the right atrium. It is large enough to admit the tips of 3 fingers; it opens into the lower and posterior part of the right ventricle and is bounded by the tricuspid valve. The surface projection of this aperture lies obliquely behind the sternum close to the midline and extends from the level of the 4th left costal cartilage to the level of the 6th right cartilage. Medial to the opening of the inferior vena cava, the coronary sinus may be found. The opening of the sinus points to the left and is guarded by a small pocketlike valve called the coronary valve (Thebesius), which turns the blood of the coronary sinus forward into the atrioventricular orifice. Right Ventricle. This chamber has a thick muscle wall and is somewhat triangular in outline. The infundibulum (conus arteriosus) is the uppermost part of the right ventricle, the walls of which are smooth and have no projecting muscular bundles; it leads into the pulmonary artery. The inner surface of the right ventricle is extremely irregular because of a lacework of muscular ridges which are called the trabeculae carnea. Some of these are attached to the wall only at each extremity, but they are free elsewhere. A number of conical muscular projections are also found; these are the papillary muscles. They are attached at their bases to the wall of the ventricle, and their apices are connected to the cusps of the tricuspid valve by a number of tendinous strands called the chordae tendinae. There is usually a large inferior papillary muscle which is attached to the anterior wall. One of these trabeculae,
FIG. Left atrium and the left ventricle. Windows have been cut into these
chambers, and arrows indicate the course of the blood stream.
which is unusually strong and well marked, passes across the right ventricle from the septum to the base of the anterior papillary muscle; it is called the moderator band. The entrance to the right ventricle is by way of the right atrioventricular orifice, and the exit is the pulmonary orifice. The right atrioventricular orifice is situated at the lower and posterior part of the ventricle; it is about 1 inch in diameter and is surrounded by a fibrous ring. It usually admits the tips of 3 fingers and is guarded by a valve which possesses 3 cusps; hence, the name tricuspid valve. One of the cusps is anterior; another, medial; and the third, inferior. They are semilunar in shape. The atrial surfaces of the cusps are smooth, but their ventricular surfaces are roughened by the attachments of the chordae tendinae. The pulmonary orifice, in the upper posterior part of the ventricle at the apex of the infundibulum, is surrounded by a thin fibrous ring to which the bases of the 3 cusps of the pulmonary valve are attached. Left Atrium. Only the auricle of the left atrium can be seen in front, and to view the remainder of this chamber, one must lift the apex of the heart upward and examine the posterior surface of the organ. The left atrium is quadrilateral in shape, and its interior reveals the openings of the 4 pulmonary veins, usually 2 on either side. These veins are unguarded by valves. The interior of the chamber is quite smooth except in its auricular portion, where musculi pectinati are present. In a fresh heart the interior of the left atrium looks much paler than that of the other chambers, because of the greater thickness of the endocardium, which can be stripped off easily, though it is quite difficult to do this in any other cardiac chamber. Blood leaves the left atrium and enters the left ventricle via the left atrioventricular orifice. This is smaller than the one on the right and admits only 2 fingers. Left Ventricle. The cavity of the left ventricle is longer and narrower than that of the right, and the walls are much thicker. Its interior reveals a dense meshwork of trabeculae carneae which are finer but
FIG. Diagram of heart chambers, valves and vessels. The arrows indicate the direction of blood flow, and the colors designate oxygenated and nonoxygenated blood.
more numerous than those of the right. However, the papillary muscles of this ventricle are less numerous and much stronger; the chordae tendinae from each papillary muscle pass to both cusps of the mitral valve. The left atrioventricular orifice is surrounded by the bicuspid (mitral) valve, which consists of a larger anterior cusp and a smaller posterior one. Blood leaves the left ventricle via the aortic orifice, which is at the upper right and posterior part, and (like the pulmonary orifice) is surrounded by a fibrous ring to which the bases of the cusps of the aortic valve are attached. The aortic valve, like the pulmonary, has 3 semilunar cusps.
BLOOD VESSELS AND NERVES The trunk of the pulmonary artery arises from the infundibulum of the right ventricle, passes upward and backward and carries the blood from the right ventricle to the lung. It is about 2 inches long and nearly 1 inch in diameter. It lies within the fibrous pericardium, being enclosed with the ascending aorta in a sheath of serous pericardium. As it passes upward, it lies between the right and the left auricles which embrace it; being in front of the aorta, it conceals the roof of this vessel. It is behind the sternal extremity of the 3rd left costal cartilage, and as it travels upward and backward, it bifurcates below the arch of the aorta like the letter “T” into right and left pulmonary arteries. This bifurcation takes place opposite the sternal end of the second left costal cartilage. The ligamentum arteriosum is a fibrous band which extends from the bifurcation of the pulmonary trunk to the lower aspect of the aortic arch. It represents the remains of the ductus arteriosus of the fetus, a vessel which short-circuits the blood from the pulmonary circulation into the aorta. The left recurrent laryngeal nerve hooks around the left side of the ligament. The pulmonary artery has the following relations: anterior, the pericardium and the left pleura and lungs; posterior, the ascending aorta and the left atrium; superior, the
FIG. The heart valves seen from above. The origins of the coronary arteries are shown.
arch of the aorta and the ligamentum arteriosum; laterally, the corresponding coronary arteries and auricles; on the right side, the ascending aorta. The right pulmonary artery is longer than the left; it commences below the arch of the aorta and passes to the hilum of the right lung. In its course, it travels behind the ascending aorta and the superior vena cava, and in front of the esophagus and the stem of the right bronchus. It divides into 3 primary branches, one for each lobe. The left pulmonary artery passes directly to the left in front of the descending aorta and the left bronchus. At the root of the left lung it divides into 2 primary branches, one for each lobe. The aorta is the great arterial trunk of the body. It is situated partly in the thorax and partly in the abdomen. It commences at the left ventricle, arches over the root of the left lung, descends in front of the vertebral column through the diaphragm and enters the abdomen. It ends opposite the left side of the body of the 4th lumbar vertebra by bifurcating into 2 common iliac arteries. It is conveniently divided into 4 parts: the ascending aorta, the arch of the aorta, the descending aorta and the abdominal aorta. The descending aorta springs from the left ventricle at the aortic orifice and travels upward and to the right. It is about
FIG. Arteries and veins of the heart: coronary arteries; the venous drainage.
right posterolateral side, and these structures pass with it through the aortic orifice in the diaphragm at a level between the 12th thoracic and 1st lumbar vertebrae. The hemiazygos vein is on its left posterolateral side. Branches arise from both the front and the back of the descending aorta. The posterior branches consist of 9 pairs of posterior intercostals arteries of the lower 9 intercostal spaces, and one pair of subcostal arteries. Those branches which arise from the front of the vessel are 2 left bronchial arteries, 4 esophageal and some small mediastinal, phrenic and pericardial branches. The coronary arteries are the nutrient vessels of the heart. They arise from dilatations of the root of the aorta, which are called the sinuses of the aorta. There are 3 such sinuses—1 anterior and 2 posterior—but only 2 coronary arteries —a right and a left. The right coronary arises from the anterior sinus, and the left from the left posterior sinus. The origins of these vessels are hidden anteriorly by the right auricular appendix and the pulmonary artery. The vessels pass forward, one on
by marking 6 points on the anterior chest wall. either side of the pulmonary artery, and have the corresponding auricular appendage to their lateral sides. The right artery travels in the right atrioventricular sulcus to the back of the heart until it reaches the beginning of the posterior interventricular groove, where it gives rise to a well-developed posterior descending interventricular branch. The left coronary artery reaches the anterior interventricular sulcus, into which it sends an anterior descending interventricular branch, and the main trunk of the artery (circumflex artery) continues around the left side of the heart to reach its posterior aspect. The course of this vessel may be obscured by fat in the left auriculoventricular sulcus. The cardiac veins accompany the arteries in the sulci and usually are superficial to the arteries. The companion of the left coronary artery is the great cardiac vein. It follows the course of the interventricular branch of the left coronary artery and the circumflex branch. The companion of the interventricular branch of the right coronary artery is the middle cardiac vein. Most of the venous blood of the heart enters the coronary sinus, which lies in the atrioventricular sulcus at the lower end of the oblique pericardial sinus. It is about 1 1/2 inches long and opens into the right atrium at the left of the orifice of the inferior vena cava. The nerves which supply the heart are derived from the vagus and the cervical ganglionated chain. They spread over the aortic arch and the heart and are distributed with the branches of the coronary vessels.
THORACIC PROJECTION OF THE HEART AND THE GREAT VESSELS
The heart and the great vessels may be projected onto the anterior chest wall in the following way. Four points are marked on the thorax. Two of these are placed in the middle of each 2nd intercostals space, and 1 inch lateral to either sternal margin. If a line joins these 2 points, it identifies the clinical base of the heart (superior border) and demarcates it from the great vessels. The 3rd point is placed just below and medial to the nipple in the left 5th intercostal space, and the 4th mark is located at the junction of the upper and the middle thirds of the xiphoid. If these 4 points are joined, the heart area is outlined quite accurately. The great vessel area is outlined by drawing a horizontal line across the manubrium about V2 inch below the suprasternal notch. This line extends a little less than 1 inch lateral to either sternal margin. Two vertical lines connect these points to the cardiac area. The internal jugular and the subclavian veins unite behind the sternoclavicular articulation to form the innominate vein. The left innominate vein is longer because it must pass obliquely behind the upper half of the manubrium to join the right innominate vein, thus forming the superior vena cava. This junction takes place behind the middle of the right border of the manubrium. The superior vena cava is thus formed in the region of the angle of Louis and continues as far as the right 3rd costal cartilage. At this point the right atrium begins and continues from the 3rd costal cartilage to the 6th, making a slight convex bulge outward; this represents the right border of the heart. The inferior vena cava enters the right atrium approximately at the level of the 6th costal cartilage. Therefore, a straight line can be drawn 1 or 2 cm. laterally to the right border of the sternum which connects the right internal jugular vein with the inferior vena cava. This line would mark the right internal jugular vein, the superior vena cava, the right atrium and the inferior vena cava. The inferior margin of the heart extends from the 6th costal cartilage on the right, near the entrance of the inferior vena cava, to the apex of the heart. It is convex and lies on the diaphragm. The cardiac apex is located in the 5th left intercostal space, approximately 3 1/2. inches from the median plane. However, this is a variable point, since it lies higher in children (4th interspace), lower in older people and is changed in pathologic conditions of the heart. The line indicating the division of the right atrium from the right ventricle (atrioventricular sulcus) is drawn from the 3rd left to the 6th right sternocostal joints. The left auricle can be indicated by drawing a small circle approximately the size of a dime at the sternal margin of the 2nd left intercostal space. The left ventricle is marked as a small strip which extends between the 3rd and the 6th left costal cartilages to the apex. Therefore, all 4 chambers of the heart may be mapped out over the stemocostal surface. The veins in this area usually lie superficial to the arteries. The ascending aorta overlaps the superior vena cava as it passes upward and to the right. The arch of the aorta passes backward and to the left, behind the lower half of the manubrium; it is below the left innominate vein. The latter crosses in front of the vein, the left common carotid and left subclavian arteries. The pulmonary artery passes upward and to the left, between the auricles. It lies in front of and hides the root of the aorta, and below the aortic arch it divides into a right and left pulmonary artery. The veins of the stemocostal area consist of the right and the left innominates. The right innominate vein passes almost vertically downward for about 1 inch, but the left, which is nearly 3 times as long, runs almost horizontally behind the upper half of the manubrium. It joins the right vein behind the lower part of the 1st right costal cartilage near its junction with the manubrium. At times the left innominate vein may appear above the suprasternal notch. This happens more frequently in children. If this should be the case, the vein is in danger in operations about the root of the neck. To the left side of the vein is the innominate artery, but the vein somewhat overlaps the artery. It is separated from the sternoclavicular joint by the sternohyoid and the sternothyroid muscles. The left innominate vein begins behind the
FIG. Surface projection of the heart valves and their areas of maximum audibility.
left sternoclavicular joint and ends by joining the right innominate to form the superior vena cava. In its oblique course it passes behind the remains of the thymus and in front of the left subclavian, the left common carotid and the innominate arteries.
AREAS OF MAXIMUM AUDIBILITY OF HEART VALVE SOUNDS AND THEIR THORACIC PROJECTION The audibility of the heart valves depends on the depth of the valves from the surface of the chest, the sound-
FIG. The Duval-Barasty incision. This provides excellent exposure of the heart and protects the pleural cavities.
transmitting quality of tissue and the direction of blood flow in the heart chambers. The tricuspid valve is heard best at the lower left quarter of the body of the sternum. This is where the right ventricle is nearest the surface. The pulmonary valve is heard best at the 3rd left costal cartilage close to the sternum. This is opposite the valve proper, since the pulmonary trunk recedes from the surface as it travels upward. The mitral valve is placed deeper than the valves of the right side of the heart; it is located posterior to the left half of the sternum on a level with the 4th costal cartilage. Its auscultatory area is in the direction of the blood flow as it passes from auricle to ventricle and is over the cardiac apex. The aortic valve sound is heard best in the second right intercostal space at the sternal margin and is projected along the course of the blood stream. The ascending aorta passes forward, upward and to the right.
SURGICAL CONSIDERATIONS EXPOSURE OF THE HEART Many incisions have been described, but only the more popular ones are considered. The Duval-Barasty incision to the pericardium and the heart gives excellent exposure and protects the pleural cavities. Its only drawback is that it takes time to open and close and may be associated with shock. The incision is made in the midline from the 2nd rib to the midepigastrium. The xiphoid is removed, and the sternum is split to the 2nd interspace where it is cut transversely. The split halves of the sternum are retracted, the pleurae pushed aside, and the pericardium opened anteriorly. The diaphragm and the anterior pericardium are incised, making the incision a thoraco-abdominal one. Spangaro’s incision is really an intercostochondral thoracotomy which provides a rapid approach to the heart but not as good exposure as does the Duval-Barasty. The incision is made through the 4th intercostals space from the margin of the sternum to the anterior axillary line. The internal mammary vessels are ligated and divided. The 4th and the 5th ribs and cartilages are separated, and the left lung is retracted. The pericardium is incised in the long axis of the heart, and the pathologic areas are exposed and treated. Parasternal and semicircular incisions which utilize flaps have also been advocated.
WOUNDS OF THE HEART The immediate dangers in heart wounds are tamponade and hemorrhage. Aspiration while preparations for the operation are being made may be lifesaving. D. C. Elkin has reviewed this subject and emphasizes that, if time permits, all efforts should be made to avoid entering the pleural cavity, since a pneumothorax adds to the shock. One of the above-mentioned incisions is utilized, and the wound in the pericardium is located and enlarged. If this is not found, the pericardium is opened between stay sutures. When the intrapericardial pressure is released, the bleeding becomes profuse, and the contractions of the heart increase in force. The greatest difficulty is encountered in placing the first stitch. When the cardiac wound is located, the index finger of the left hand is placed over it, and the surrounding blood is removed by suction. The first suture is placed directly beneath the finger and may be used for traction and hemostasis. Then the wound is closed with unabsorbable suture material, the sutures passing into the muscle but not into the heart chambers. Claude Beck has emphasized the fact that wounds located in the edges of the heart, on its posterior surface, or behind the sternum are reached best by placing an apex suture. By this method the heart may be rotated so that the injury can be exposed properly. Beck’s control suture steadies the heart while the other sutures are being placed. The pericardium should be closed loosely with interrupted sutures so that space is allowed for drainage of the intrapericardial fluid which will accumulate. Muscle, fascia and skin are closed in layers.
PERICARDIECTOMY Warren Cole, Weber and Keeton have described a technic of pericardiectomy for constrictive pericarditis. They state that the excision of the scar should be started over the
FIG. Corbiloculare—the primitive
2-chambered heart. left ventricle, and an attempt should be made to find a cleavage plane between the scar and the cardiac musculature. Dissection continues in this plane. Since all landmarks are usually obliterated, the coronary vessels may be difficult to find, and injury to these vessels is dangerous. Harrington has stressed the importance of epicardiolysis as well.
CONGENITAL DEFECTS Congenital defects of the heart and the great vessels were described as early as 1777 by the eminent Dutch physician Sandifort, who gave a remarkably clear description of what is known today as the “tetralogy of Fallot.” One of the most prolific contributors to the knowledge of these anomalies was Maude E. Abbott. To her goes the credit in a large measure for being responsible for today’s diagnostic precision which resulted in a new and gratifying field of surgery. When one discusses these dramatic events, the names of Bailey, Blalock, Crafoord, Gross and Taussig must be mentioned also. In a book of this type the many cardiac anomalies are too numerous to be mentioned. Some of the more common ones will be described so
FIG. Cor triloculare biatriatum—the 3-chambered heart.
FIG. The tetralogy of Fallot.
as to give the student of surgical anatomy a mere taste of this intriguing field of study. Cor Biloculare (2-Chambered Heart). This is a most primitive type of cardiac defect Tt has a single atrium, a single ventricle and a common atrioventricular valve. It must be remembered that many anomalies may appear in a given specimen. Therefore, in the diagram herein presented it will be noted that the pulmonary artery lies behind the aorta and is atretic. Pulmonary circulation takes place via a patent ductus arteriosus. Death ensues in these patients in infancy or early childhood. Cor Triloculare Biatriatum (3-Chambered Heart) consists of 2 atria and a single ventricle. No ventricular septum exists, and in the diagram shown here there is an associated transposition of the aorta and the pulmonary artery. It resembles the 2-chambered heart in that there is a free admixture of venous and aerated blood in the single ventricle. The chances of survival are somewhat greater than in the 2-chambered heart, although death occurs commonly during infancy.
FIG. The Potts operation for tetralogy of Fallot. This illustration depicts a left-sided approach and a Potts clamp applied to the mobilized aorta. This clamp allows flow of blood through part of the aortic lumen. The pulmonary artery is temporarily obstructed proximally and distally to the site of anastomosis.
FIG. The Blalock-Taussig anastomosis of the right subclavian branch of the innominate artery to the right pulmonary artery for tetralogy of Fallot.
FIG. Diagrammatic presentation. FIG. A patent ductus arteriosus.
of the Eisenmenger complex
The tetralogy of Fallot as originally described consisted of
1. Pulmonary stenosis (atresia)
2. Dextraposition of the aorta
3. Interventricular septal defect
4. Hypertrophy of the right ventricle
This is the most common malformation associated with cyanosis which permits the patients to survive beyond 2 years of age. Potts and Blalock have attempted to correct the pulmonary stenosis by creating an artificial ductus arteriosus. Potts accomplished this by performing a side-to-side anastomosis between the pulmonary artery and the aorta. The Blalock procedure consists of an end-to-side anastomosis between a systemic branch of the aorta (subclavian) and one of the 2 pulmonary arteries. Numerous modifications of these procedures have been described. The Eisenmenger complex reveals a heart that has a ventricular septal defect with biventricular origin of the aorta. The aorta straddles a defect in the membranous portion of the ventricular septum. Because of this the right and the left ventricles share in the propelling of blood into the aorta; the pressure in the 2 ventricles is similar, being at systemic levels. In the Eisenmenger complex the small arteries in the lungs closely resemble those of the normal fetus in which there is increased resistance to pulmonary blood flow. Patent ductus arteriosus permits blood to flow from the aorta into the pulmonary artery. It should be recalled that during fetal life the ductus arteriosus is a normally functioning channel which short-circuits blood from the pulmonary artery to the aorta. This should become obliterated at or shortly after birth. If the ductus remains open, great volumes of blood reach the pulmonary artery via the aorta and are reflected in a left ventricular dilatation and hypertrophy. Two types of patent ductus arteriosus have been described: one in which it is cylindrical and one in which it is stubby, the latter being known as the window type. Evidence of progressive cardiac failure in an acyanotic infant strongly suggests the possibility of this condition. The patient frequently lives to adult life; however, life expectancy is reduced materially. Among the chief causes of death in untreated cases are bacterial infection and left ventricular failure. The closure of a patent ductus arteriosus is now a standard surgical procedure.
A patent ductus should be ligated or di-
FIG. Operation for patent ductus arteriosus.
vided to improve circulatory function and to diminish the hazards of blood stream infection. The operation is performed usually through an incision in the left mammary fold as advocated by Gross. This extends from the sternum to the anterior axillary line. The breast is reflected cephalad, and the soft tissues are divided so that the 3rd and the 4th costal cartilages are exposed. The pleural cavity is entered through the 3rd intercostal space, the 3rd and 4th cartilages are divided, and the ribs retracted. The lung is retracted, the mediastinal pleura incised, and the arch of the aorta and the pulmonary artery exposed. The phrenic and the vagus nerves are identified and mobilized, and the patent ductus is completely exposed. The latter is divided between clamps and carefully sutured. Harrington has expressed the belief that the older an individual grows the shorter the ductus becomes, so that in adults the duct has really become an arteriovenous fistula. The parietal pleura of the mediastinum is sutured, and closure of the chest wall is accomplished in layers. Coarctation of the Aorta. This narrowing or constriction can occur anywhere in this vessel from the midpoint of the arch down to its bifurcation. However, very few are found in the abdomen or the lower thorax. But 98 per cent of coarctations are located in the first part of the descending aorta just beyond the arch.
There has been a tendency to divide this condition into two distinct forms. In the first, the so-called “infantile type,” there is a long segment of constriction, and it is associated with severe intracardiac abnormalities, commonly leading to death within the first few years of life. The second, the so-called “adult type,” was supposed to have a blockage of a short segment and be prone to involve the aorta beyond the origin of the left subclavian artery. Hence, it is not accompanied by marked intracardiac malformations, and the prognosis is better for life into adult years. Modern authorities in this field believe that there is little point in classifying coarctations of the aorta into these two artificial groups because of the tremendous amount of overlapping, thus making the classification useless. Some authors are of the opinion that the relationship of coarctation to the ligamentum arteriosum (obliterated ductus arteriosus) is important. Probably more important than this relationship is the advisability of determining whether or not the ductus arteriosus is patent. Collateral arterial circulation is rarely seen in children but may be detected after the 1st decade, particularly in thin subjects. Pulsations may be seen and felt above and below the clavicles, in the axillae, in the intercostal spaces, particularly in the forward half of the chest, in the epigastrium and over the upper half of the back. When collateral circulation is marked, these pulsations may appear in the anterior abdominal wall; at times they have been traced down as far as the inguinal regions. Some of the causes of death from coarctation of the aorta are left ventricular failure, rupture of the aorta, bacterial endocarditis and rupture of an aneurysm of the Circle of Willis. Surgical correction of the condition is accomplished in one of three ways: (1) the ideal correction is removal of the narrow segment with an end-to-end anastomosis between the proximal and the distal ends of the aorta; (2) a bypass procedure has been advocated in which the left subclavian artery has been anastomosed to the distal end of the aorta; (3) resection of the constricted
FIG. Diagrammatic representation of the collateral circulation in coarctation.
FIG.A. Diagrammatic representation of an atrial septal defect. The arrows indicate the possible flow of blood.
segment with the insertion of a graft between proximal and distal ends of the aorta. Atrial septal defect is among the commoner types of congenital cardiac anomalies, particularly those seen in adult life. The usual form of this defect is a valvular incompetence of the foramen ovale. This defect allows oxygenated blood to flow from the left atrium to the right atrium, thus resulting in a recirculation of oxygenated blood through the lungs. Such defects, if appreciable, cause dilatation and hypertrophy of the right ventricle, enlargement of the right atrium, and enlargement of the pulmonary trunk and its branches. There is no cyanosis so long as the shunt is arteriovenous. Symptoms may be absent or minimal, and in the extreme instances congestive heart failure and sudden death may occur. On occasion an embolus may escape through an
FIG.B. Ventricular septal defect. The arrows indicate the possible flow of blood.
atrial septal defect, resulting in a phenomenon known as “paradoxical embolism.”Ventricular septal defects may occur in either the membranous or the muscular portions of the ventricular septum.This defect permits the shunt of blood from the left ventricle to the right ventricle, producing an increased load of work on both ventricles. Patients who survive the 1st year of life with such defects may live many years without disability and reach adulthood with few signs, if any, and no cardiac enlargement. Bacterial endocarditis is a common complication in patients who survive infancy.
SURGERY OF THE AORTA Alexander and Byron have reported a case of aortectomy. The problem of collateral circulationis interesting. Gitlow and Sommer have reported a case of complete coarctation in which the collateral circulation took place chiefly by way of the internal mammary, the superior intercostals and the subscapular arteries. Bramwell and Jones studied the collateral circulation in a case of complete aortic coarctation which occurred just distal to the left subclavian artery. They conclude that the main anastomoses were: (1) the musculophrenic branches of the internal mammary to the inferior phrenic branches of the abdominal aorta, and the superior phrenic branches of the thoracic aorta which formed a network above and below the diaphragm; (2) via the scapular and the cervical branches of the subclavian and the axillary arteries, to the lateral dorsal branches of the aortic intercostal; (3) via the superior intercostals through the upper two, to the next lower intercostals. However, Alexander and Byron have stressed that in their case much of the collateral circulation took place through the superior and the inferior epigastric arteries. Ochsner and
Azygos System of Veins and
The azygos system consists of 3 veins which form longitudinal collecting trunks into which the intercostal veins drain: azygos (vena azygos major) the hemiazygos (vena azygos minor inferior) and the accessory hemiazygos (vena azygos minor superior). The azygos is located on the right side, and the hemiazygos and the accessory hemiazygos on the left. The right and the left ascending lumbar veins constitute the most caudal portion of the system and drain into the azygos and the hemiazygos, respectively. These veins, because they link together the superior and the inferior venae cavae, constitute important anastomosing channels. The azygos vein begins in the abdomen, approximately where the renal vein enters the inferior vena cava. Its origin is variable, but most anatomists are of the opinion that it arises from the posterior aspect of the inferior vena cava; however, others have described its origin as being formed by the union of the right ascending lumbar and subcostal veins, whereas still others consider it as a branch of the right renal vein. It enters the thorax on the right side of the thoracic duct and the descending aorta, passes upward in front of the vertebral bodies and is overlapped by the right edge of the esophagus. It passes into the thorax through the aortic opening of the diaphragm. At the upper border of the root of the right lung, it emerges from under cover of the esophagus, arches forward above the right bronchus and terminates in the superior vena cava. Therefore, this vein has vertical and horizontal portions and is related to the mediastinal aspect of the right lung and the pleura. Although it has imperfect valves, its tributaries have complete ones. The tributaries are formed by numerous small veins such as the esophageal, the pericardial, the bronchial and the mediastinal; in addition to these, it receives the 2 hemiazygos veins, the lower 8 posterior intercostals (subcostal) of the right side, and the right superior intercostal vein. The last is the common trunk formed by the union of the veins from the 2nd and the 3rd intercostal spaces. The hemiazygos vein (vena azygos minor inferior) begins in the left ascending lumbar or renal vein. It enters the thorax through the left crus of the diaphragm, ascending on the left side of the vertebral column as high as the 9th thoracic vertebra, where it passes across the column and behind the aorta, the esophagus and the thoracic duct to end in the azygos vein. In its course, it crosses 3 or 4 of the lower left intercostal arteries and is covered by the pleura. It receives the lower 4 or 5 left intercostal veins, at times the lower end of the accessory hemiazygos, the small left mediastinal and the lower left esophageal veins. The accessory hemiazygos vein (vena azygos minor superior) varies much in size, position and arrangement, since it is often continuous with or drained by the left superior intercostal vein. Therefore, it varies inversely in size with the left superior intercostal. It descends on the left side of the vertebral column and receives veins from the 3 or 4 intercostal spaces between the superior left intercostal and the highest tributary of the hemiazygos; it either crosses the body of the 8th thoracic vertebra, emptying into the azygos, or ends in the hemiazygos. If it is very small or entirely absent, the left superior intercostal extends as low as the 5th or the 6th intercostal space. If the inferior vena cava is obstructed, the azygos and the hemiazygos vein s are one of the principal means by which collateral venous circulation is carried out, since they connect the venae cavae and communicate with the common iliac veins via the ascending lumbar and with many tributaries of the inferior vena cava. For additional study of the azygos system of veins and its variations and anomalies, one can refer to the works of Seib, Huseby and Boyden and of H. Neuberger. The superior vena cava is about
Thoracic Duct
EMBRYOLOGY In the fetus, the thoracic ducts are a pair of vessels which ascend through the posterior mediastinum on each side of the descending thoracic aorta. They continue through the superior mediastinum, on each side of the esophagus, to the root of the neck where each arches laterally, immediately behind the carotid sheath, and opens into the angle between the subclavian and the internal jugular veins. Because of pressure from the aorta, the left duct atrophies; the right persists, crosses to the left side and empties into the left subclavian vein. The disappearance and the persistence of the ductus is subject to great variation, so that any arrangement of anastomoses may result. Jossifow described some of these variations and the level of formation.
THE ADULT DUCT The adult duct is approximately the same length as the spinal cord,about
Sympathetic Chain
The term “autonomic” implies autonomous or self-controlling. It suggests automatic regulation without cerebral control, in this instance, of visceral functions. Therefore, the autonomic nervous system controls the motor functions of the viscera, since it controls all smooth (involuntary) muscle, cardiac muscle and glands. In general, most viscera are supplied by two opposing sets of nerves which are antagonistic to each other; when one stimulates, the other inhibits activity. Both the stimulating and the inhibiting mechanisms require a 2-neuron chain between the nucleus of origin in the central nervous system and the peripheral organ which is to be innervated.
Such a system requires a synapse between the 2 neurons which occurs in ganglia outside of the central nervous system. The ganglion may be used as a point of reference, since the fibers lying closest to the brain or the spinal cord are called preganglionic (presynaptic) fibers. The second fiber, the cell of origin of which lies in one of the ganglia and carries impulses to an organ, is known as a postganglionic (postsynaptic) fiber. Hence, the autonomic nervous system resembles the somatic in that it consists of central and peripheral parts. The central elements of the autonomic system are intrinsic parts of the central nervous system, being located in the cerebral cortex, the hypothalmus, the brain stem, the cerebellum and the spinal cord. Many authorities believe that there is no actual nerve tissue contact between autonomic nerves and the structures supplied by them, but that the resultant action comes from a liberation of chemical substances resembling epinephrine (Adrenalin) and acetylcholine, and the divergent effects produced thereby are often referred to as adrenergic and cholinergic, respectively. Such a concept presupposes the existence of definite nerve endings with junctional zones between them and the viscera innervated. It has become customary to divide the
autonomic nervous system into 2 major portions based on the origin of the preganglionic fibers from the central nervous system. The preganglionic fibers which arise from the thoracic and the lumbar spinal cord are referred to as the thoracolumbar (sympathetic) part. The preganglionic fibers which originate either in certain cranial nerve nuclei or the sacral part of the spinal cord are referred to as the craniosacral (parasympathetic) part. The sympathetic trunks enter the thorax from the neck and descend in front of the heads of the ribs and in front of the posterior intercostal vessels and nerves. The thoracic trunks usually have 10 or 11
FIG. Thoracic sympathectomy (posterior approach)
separate ganglia which vary in size; occasionally, there may be 12. The 1st thoracic ganglion is frequently fused with the inferior cervical sympathetic ganglion to form the stellate (cervicothoracic) ganglion. The 2nd thoracic ganglion may be fused with the first. The remaining thoracic ganglia frequently lie at the levels of the corresponding intervertebral disks. The portion of the sympathetic trunk between two adjacent ganglia may be double and at other times may appear very slender. The sympathetic trunks enter the abdomen via the diaphragm by passing behind the medial lumbocostal arches. The trunks and the ganglia are connected with the ventral rami of the thoracic nerve by means of rami communicantes which supply branches to adjacent viscera and blood vessels and then send splanchnic nerves into the abdomen. Each ganglion has from 1 to 4 rami communicantes which connect it with the corresponding nerves; connections may also be made with the nerve above or the nerve below. Three ganglionic sympathetic fibers in the spinal nerves reach the sympathetic trunk by way of these rami communicantes. Postganglionic fibers from the trunk and the ganglia to these nerves also course in these rami. Sensory (pain) fibers from the thoracic and the abdominal organs pass through the rami and thus reach the spinal nerves and the dorsal routes. Although one cannot be too dogmatic in teaching, it may be safe to state that the thoracolumbar outflow is a mechanism associated with emergency situations in contrast with the conservatism of the craniosacral outflow. On the basis of this concept, we may now enumerate specific reactions which result from activation of the thoracolumbar system:
1. The pupil of the eye dilates because of excitation of the dilator pupillae muscle. 2. The blood pressure becomes elevated because of vasoconstriction, both peripheral and visceral.
3. The cardiac rate is increased.
4. Visceral musculature is inhibited.
5. External sphincters are activated, thus resulting in spasms.
6. The salivary and the digestive glands are inhibited in their activities.
7. The adrenal medulla is activated and pours out epinephrine, enhancing and reinforcing all of the above-mentioned responses.
SURGICAL CONSIDERATIONS
SYMPATHECTOMY Sympathectomy may be helpful in dealing with causalgia, painful post-traumatic arthritis, painful amputation stump and the phenomenon of phantom limb. In these conditions the upper thoracic ganglia can be blocked temporarily with procaine, and the effect recorded. When pain recurs within a few hours after such injections, the sympathetic connections should be destroyed permanently. It is best to employ the preganglionic type of sympathectomy, as the effect of this operation is believed to be due to the elimination of vasomotor impulses and not to interruption of sensory fibers. The physiologic reasons for this have been well described by White and Smithwick. Sympathectomy as a form of treatment for hypertension will be discussed presently. Whether it is desired to resect the upper thoracic sympathetic ganglia or to sever their central connections, the exposure is the same. The patient is placed on the operating table face down, with several pillows under the chest. The incision is made 5 cm. lateral and parallel with the spinous processes; it is 10 cm. in length and centered over the ribs to be resected. The trapezius, the rhomboid minor and major, and the serratus posterior superior muscles are divided. The lateral border of the erector spinae and the overlying muscles are retracted. This exposes the rib and the transverse process to be resected. The rib is separated from the intercostals muscles and the underlying pleura and is cut off 4 cm. lateral to its articulation. The pleura is stripped away, and the sympathetic chain is located. It is best to divide the trunk below the 3rd thoracic ganglion first and then work upward, freeing it from the sides of the vertebrae and cutting its rami.
RECOMMENDED LITERATURE:
1. Mark W. Wolcott. Ambulatory Surgery End The Basic Of Emergency Surgical Care.-Philadelphia:J.B.Lippincott Company,2001.-752p.
2. Michael F. Mulroy.Regional Anesthesia /The
3. Richard M. Stilman,M.D.,E.A.C.S. General Surgery /Review And Assessment/
4. Kent M. Van De Graff, Stuart Ira Fox, Karen M. Lafleur. Synopsis of Human Anatomy and Physiology /WCB McGraw-Hill/, 2004.-675p.
5. John J. Jacobs. Shearer’s Manual Of Human Dissection /McGraw-Hill Information Services Company, 1998.-300p.
6.
7. Philip Thorek. Anatomy In Surgery /J.B.Lippincott Company/,1996.-935p.
