Employment 5. Surgical anatomy of neck organs (thyroid gland, larynx, pharynx, esophages). Blood supply, venous and lymphatic drainage, innervation. Tracheostomy. External approaches to esophages. Operative intervention on neck organs.
THYROID GLAND
Embryology. At the junction of the posterior third with the anterior two thirds of the tongue, the foramen caecum is noted as a small depression. From this site at an early stage of fetal life, a solid column of cells grows downward, becomes canalized and forms the thyroglossal duct, from which the thyroid gland is formed. The duct passes down exactly in the midline between the genioglossi muscles as far as the upper border of the thyroid cartilage, where it turns to one or the other side of the midline. From this point on its course is represented by the pyramidal lobe. The question whether the thyroglossal duct passes in front of, through, or behind the body of the hyoid bone seems to have been answered by Frazer who has shown that it is placed in front of the bone and then takes a recurrent course up behind the hyoid before continuing downward. For this reason many advocate removal of the midportion of the hyoid to make certain that the entire tract is eliminated. If the duct remains open after birth, thyroglossal cysts develop either above the thyroid cartilage where they are usually centrally placed, or below the cartilage where they are usually found to the left of the midline. Since the thyroglossal duct never opens onto the surface of the neck at any stage of its develop-
FIG. Obstruction of the internal carotid artery. (A) A bypass graft has been placed. (B) Removal of the offending clot and widening of the vessel by an elliptical patch.
ment, congenital thyroglossal fistula is impossible. However, fistulae do occur as a result of bursting or opening of a thyroglossal cyst onto the surface. Accessory thyroid glands may occur anywhere along the line of the duct and are sometimes found at the back of the tongue (lingual thyroids).
Thyroid Gland Proper. The adult thyroid is a ductless gland. It is a highly vascular, solid organ related to the pretracheal fascia, that binds it to the larynx and causes it to rise and fall during the act of swallowing. It possesses its own true fibrous capsule, which is continuous with the stroma of the gland. The thyroid consists of a pair of lateral lobes which are joined across the median line by the isthmus. Each lateral lobe extends from the middle of the thyroid cartilage to the 6th tracheal ring, is pyramidal in shape with its apex upward and measures
FIG. Embryology of the thyroid gland: (A) course of the thyroglossal duct, (B) lateral view of the thyroglossal duct and possible locations of accessory thyroid glands.
FIG. The thyroid gland. (A) The gland has been presented as a transparent structure to show the relations of the vessels and nerves. The path of the interior thyroid artery can be followed. (B) Cross section through the isthmus of the thyroid gland. (C) The thyroid gland viewed from the left side. The gland is in relation to 2 nerves (recurrent and external laryngeal), 2 tubes (esophagus and trachea) and 2 muscles (inferior constrictor and cricothyroid).
hyoid and the sternothyroid and is overlapped by the sternocleidomastoid muscle. The isthmus, which occasionally is absent, is a bar of thyroid tissue, varying in width and lying under cover of the skin and the fascia in the median line of the neck. It is situated on the 2nd, the 3rd and the 4th tracheal rings and is nearer the lower than the upper pole. A triangular projection, or pyramidal {middle) lobe, extends upward usually from the left side of the upper border of the isthmus and is connected to the hyoid
FIG. 142. The vessels of the thyroid gland: (A) the isthmus has been cut and the lower part of the left lobe removed to show the relationships of the superior and the inferior thyroid arteries and the recurrent laryngeal nerve; (B) the lymph drainage of the thyroid gland; (C) the veins of the thyroid.
bone by a fibromuscular slip called the levator glandulae thyroidae.
Arteries. The arteries of the thyroid gland are 2 pairs, the superior and the inferior thyroids, and sometimes a single artery, the thyroidea ima. The superior thyroid artery is the first branch of the external carotid; it supplies infrahyoid, laryngeal and sternocleidomastoid branches in the carotid triangle. It passes down under cover of the “strap” muscles and at the superior pole of the thyroid gland trifurcates into an anterior branch that supplies the front of the gland, a posterior that goes behind and an isthmic (arcuate) branch that joins its fellow of the opposite side along the upper border of the isthmus. The superior laryngeal nerve is situated only a little higher than the superior thyroid artery and, if the vessel is grasped too high, the nerve may be included in the ligature. The inferior thyroid artery is a branch of the thyrocervical trunk which arises from the first part of the subclavian. Although the superior vessel enters the superior pole, the inferior thyroid does not enter at the inferior pole of the gland. It travels upward along the medial border of the scalenus anterior muscle as far as the level of the 6th cervical vertebra and turns medially behind the vagus nerve and the common carotid artery. It passes in front of the vertebral vessels and, continuing downward, reaches the posterior border of the gland to which it is finally distributed. To do this it makes a hairpin turn, the summit of which varies considerably as to its level. It also supplies the larynx, the pharynx, the trachea, the esophagus and the surrounding muscles. As the artery reaches the thyroid it is crossed either in front or behind by the recurrent laryngeal nerve. A large branch of the vessel ascends along the posterior border of the gland to anastomose with a descending branch from the superior thyroid artery. The thyroidea ima is a branch from the innominate or the aortic arch. It varies in size from a tiny arteriole to a vessel as large as the inferior thyroid, which it may replace. It passes upward over the anterior surface of the trachea, under cover of the thymus, and reaches the inferior border of the isthmus. Its presence should be kept in mind when performing a low tracheostomy and during thyroid surgery. The accessory thyroid arteries are small vessels supplying the esophagus, the trachea and the thyroid gland. The 4 major thyroid arteries may be ligated, but the blood supply to the gland remains surprisingly good because of these accessory vessels.
Veins. The veins of the thyroid form a rich plexus situated in front of the gland. As they leave the gland, they form 3 main trunks in the form of superior, middle and nferior thyroid veins. The superior thyroid vein is the only venous trunk that accompanies the artery of the same name. It leaves the upper part of the gland, taking as its guide the outer border of the omohyoid muscle, crosses the common carotid artery and ends in the internal jugular vein. The middle thyroid vein has no accompanying artery. It leaves the gland about its midportion, follows the inner border of the omohyoid, crosses the common carotid artery and ends in the internal jugular vein. The inferior thyroid veins commence at the lower pole of the gland and at the lower border of the isthmus; they pass downward in front of the trachea and may be connected by several transverse branches and end in the left innominate vein. Nerves. Two nerves are related to the thyroid gland: the superior and the recurrent (inferior) laryngeal. Both are branches of the vagus nerve. The superior laryngeal nerve arises from the inferior ganglion (nodosum), passes downward and medially and crosses behind the internal carotid artery. It divides into the internal and the external laryngeal nerves. The internal laryngeal nerve, the larger of the two branches, is accompanied by the superior laryngeal branch of the superior thyroid artery and with it pierces the thyrohyoid membrane at the posterior border of the thyrohyoid muscle. It is purely sensory and supplies fibers to the floor of the piriform fossa and the mucous membrane of the larynx above the vocal cord. The external laryngeal nerve accompanies the superior thyroid artery but is placed on a deeper plane. It passes deeply to the upper pole of the thyroid gland and is distributed to the cricothyroid and the inferior constrictor muscles. During ligation of the superior thyroid vessels, the external laryngeal nerve (nerve to the cricothyroid) is in danger. It may be included in the ligature, and such inclusion would cause a weakness or huskiness of the voice. However, this condition is temporary and becomes normal within a few months. The recurrent {inferior) laryngeal nerve is a structure of vital importance in thyroid surgery. Considerable variations in its position may take place so that the nerve may penetrate and traverse the gland proper, may be behind the gland, or may remain in the tracheo-esophageal groove. During thyroid surgery, when the gland is dislocated forward and medially, the nerve usually hugs the side of the trachea. Then it is located not in the tracheo-esophageal groove but on the posterolateral aspect of the trachea. It always passes posterior to the joint that exists between the inferior cornu
FIG. The nerve supply of the thyroid gland: (A) the thyroid isthmus has been cut to show the course of the recurrent laryngeal nerve; (B) the nerves are shown on the left, and the arteries on the right.
FIG. 144. Possible locations of the recurrent laryngeal nerve: (A) behind the inferior thyroid artery; (B) in front of the inferior thyroid artery; (C) high origin, this accounts for the inability to find the nerve during thyroidectomy; (D) origin around the inferior thyroid artery; (E) extralaryngeal division. In some instances the nerve may pass between the branches of the artery.
of the thyroid and the cricoid. This cartilaginous prominence formed by the joint is a valuable guide to the nerve. On the right side the recurrent leaves the vagus nerve as it crosses the first part of the subclavian artery, turns upward and medially behind that artery and the common carotid and travels in the groove between the trachea and the esophagus. It ascends in this groove to the lobe of the thyroid gland and crosses or is crossed by the inferior thyroid artery. Upon reaching the lower border of the inferior constrictor muscle it passes deeply to it so as to gain access to the muscles of the larynx. It supplies the muscles that act on the vocal folds but also supplies sensory branches to the mucous membrane of the larynx below these folds. Therefore, it is both sensory and motor. On the left side, the nerve arises within the thorax after turning around the arch of the aorta and then ascends in the neck in the tracheo-esophageal groove. To aid in the exposure of the recurrent laryngeal nerve, M. M. Simon has constructed an anatomic triangle which can be identified readily. It is bounded by the recurrent laryngeal nerve anteriorly, the common carotid artery posteriorly, and the inferior thyroid artery forms its base. The triangle is dependent on the variations and the anomalies that may take place. The recurrent laryngeal nerve supplies all the intrinsic muscles of the larynx with the exception of the cricothyroid. There is a voluminous and confusing literature concerning the innervation of the larynx. Some of this confusion resulted from the difficulty of interpreting the various positions of a paralyzed vocal cord. To add to the confusion, a completely paralyzed or cadaveric cord may resume normal function, and a presumably incompletely paralyzed vocal cord would remain unchanged in a position of adduction with good tension for decades. The variety of responses and positions has been clarified and explained by the works of King and Gregg, who directed attention to the anatomic reasons for these various positions. They state that some recurrent laryngeal nerves divide into two trunks extralaryngeally, thus supplying fibers to the abductor and the adductor muscles, respectively. On the basis of these findings one can assume that if a paralyzed vocal cord is observed in the midline with good tension, the recurrent nerve is divided extralaryngeally, and the posterior division, which supplied the abductor muscle, has been injured. The abductor group of muscles, thus being unopposed, have pulled the vocal cord to the midline. In such a patient there would be no dyspnea, and the speaking voice would be normal. If a vocal cord is completely paralyzed (cadaveric) and is in an inter-
FIG. Simon’s triangle. This aids in the identification of the recurrent laryngeal nerve. It is bounded anteriorly by the recurrent nerve, posteriorly by the common carotid artery, and the inferior thyroid artery forms its base. The inferior horn of the thyroid cartilage also makes an excellent guide to the nerve.
FIG. Transverse sections through the larynx (vocal cord level): (A) normal glottic space; (B) early bilateral abductor paralysis, the patient can breathe but the voice is impaired; (C) late bilateral abductor paralysis, voice improves but dyspnea and inspiratory laryngeal stridor appear; (D) anatomic relations.
FIG. Ligations of the superior and the inferior thyroid arteries: (A) incisions, (B) ligation of the superior thyroid artery, (C) ligation of the inferior thyroid artery, (D) transverse section, showing the ligation of the inferior thyroid artery.
FIG.(Facing page). Subtotal thyroidectomy.
(A) The incision is placed in a transverse skin crease. (B) The investing layer of deep cervical fascia is opened along the anterior border of the sternocleidomastoid muscle. (C) Division of the sternohyoid and the omohyoid muscles on the right. The same is done on the left side. These muscles should be severed high so that their nerve supply (ansa hypoglossi) is not injured. (D) The sternohyoid and the omohyoid muscles have been dissected upward and downward. The sternothyroidon the right side has been severed. (E) Isolation and division of the middle thyroid vein; this permits entrance into the posterior thyroid space. (F) Ligation of the superior thyroid vessels.
FIGURE (Caption on facing page.)
FIGURE (Caption on facing page.) . Subtotal thyroidectomy (Continued). (G) Identification of the recurrent laryngeal nerve and ligation of the inferior thyroid artery. (H) Ring of forceps placed into the right lobe. Each hemostat bites into thyroid tissue proper and in this way protects the recurrent laryngeal nerve and the parathyroid glands. (1) Removal of the right lobe, the isthmus and the pyramidal lobe. (J) Protective ring of forceps in place; each hemostat is replaced by a ligature. (K) Approximation of the thyroid remnant. (L) Closure.
mediate position between abduction and adduction, then it must be assumed that theentire Jaryngeal nerve has been injured. In such a patient there would be marked hoarseness and an absence of dyspnea. The effects of such an injury could be compensated if the opposite normal cord is capable of crossing the midline. Therefore, it is important to notice on examination of the larynx whether or not a vocal cord fails to move and also to determine its position and tension. If both recurrent nerves are cut (bilateral abductor paralysis) the vocal cords become lax and cannot be tensed. This results in immediate impairment of voice but rarely causes difficulty in breathing. It is interesting to note that within 3 to 5 months the voice begins to return. This is due to a fibrosis and shrinking of the vocal cords which were previously lax. A few weeks later, the fibrotic process results in fixation of the vocal cords as they approach each other. The fibrotic contraction causes the cords to approach the midline, narrowing the glottic space to a thin slit. As a result of this, dyspnea begins to make its appearance, especially on exertion, resulting in a marked limitation of physical effort. The sympathetic nerve supply to the thyroid gland is derived from the sympathetic ganglia. The fibers from the middle and the inferior cervical ganglia reach the gland as nervous networks along the superior and the inferior thyroid arteries.
Lymph Drainage. The thyroid gland is drained by 2 sets of lymph vessels, the ascending and the descending, each consisting of medial and lateral groups. The medial group of the ascending vessels leaves the upper border of the isthmus and passes to the lymph glands situated on the cricothyroid membrane; they are known as the prelaryngeal glands. The lateral ascending vessels leave the upper part of the gland and accompany the superior thyroid artery to the deep cervical chain that is situated at the bifurcation of the common carotid. The medial descending vessels pass to the glands on the trachea, the pretracheal glands. The lateral descending vessels pass from the deep surface of the thyroid to small glands placed about the recurrent laryngeal nerve.
SURGICAL CONSIDERATIONS
LIGATIONS OF THYROID VESSELS
Ligation of the
Ligation of the Inferior Thyroid Artery. The most common approach is along the medial border of the sternocleidomastoid, but it has been approached along the lateral border. For the mesial approach, an incision is made along the anterior border of the sternocleidomastoid muscle. Transverse incisions produce less scarring. The incision is made through the superficial layer of deep cervical fascia, and the sternocleidomastoid muscle is retracted laterally. Dissection is continued in the interval between the carotid sheath and the thyroid gland. The middle thyroid vein is severed before the proper cleavage plane is found, and the recurrent laryngeal nerve must be avoided. Isolation and ligation of this vessel as it is done in routine thyroidectomies is described in detail elsewhere.
THYROIDECTOMY
Subtotal Thyroidectomy. This operation is performed frequently, and since technical errors might result in disaster, any anatomic points that make for a safer operation should be stressed. The incision should be so placed that the average string of beads will cover the scar. No fixed point can be mentioned, since necks vary in their length, but generally these incisions should be 1 or 2 fingerbreadths above the sternal notch and extending from one sternocleidomastoid to the other. This is deepened until the subplatysmal cleavage plane is reached. Having found this avascular plan, the upper flap, consisting of skin, subcutaneous fat and platysma, is grasped and dissected upward, well above the level of the notch of the thyroid cartilage. This exposes the superficial layer of deep cervical fascia and the anterior jugular veins. The anterior borders of the sternocleidomastoid muscles are now identified; the investing layer of deep cervical fascia is incised here. In this way the prethyroid muscles are separated from the sternocleidomastoid which is mobilized. The latter is retracted outward, and adequate exposure of the prethyroid muscles is obtained. A vertical incision is made in the midline between the two prethyroid muscle bundles and is extended from the thyroid notch to the level of the sternal notch. The sternohyoid and the omohyoid are clamped and divided high, thus protecting their nerve supply. It is an error to state that the prethyroid muscles have been severed, since the underlying sternothyroid usually remains intact after this step. A distinct cleavage plane exists between the sternohyoid and the sternothyroid. The sternohyoid and the omohyoid, having been incised, are dissected both upward and downward. The sternothyroid muscle is severed transversely, exposing the thyroid gland. The last maneuver opens the so-called “surgical capsule”. The gland is grasped by forceps, rotated medially, and the internal jugular vein in the carotid sheath is retracted laterally. This maneuver places the thin pretracheal fascia, on the stretch, where it attaches to the thyroid gland, and in this tissue the middle thyroid vein is sought. It is severed and ligated, and the posterior thyroid space is entered (Fig. 148 E). This permits medial dislocation of the gland. With medial traction on the thyroid, and lateral traction on the carotid sheath, dissection takes place in the proper cleavage plane. The upper pole is identified, as is the entrance of the superior thyroid vessels. These are doubly ligated, off the pole, and severed. Careful separation of the pretracheal layer of pretracheal fascia will reveal the recurrent laryngeal nerve and the inferior thyroid artery. If deemed necessary, the artery is ligated. A ring of forceps is placed around the right thyroid lobe which includes the isthmus; each forceps grasps thyroid tissue proper. The lobe, the isthmus, and the pyramidal lobe are removed above this protective ring. The clamped thyroid tissue is ligated, and the thyroid that remains is approximated to itself or sutured to the pretracheal fascia. The left lobe is removed in similar fashion. The severed muscles are resutured; and the skin, the superficial fascia and the platysma are approximated as one layer.
Total thyroidectomy is usually done for carcinoma of the thyroid. On the involved side the sternocleidomastoid muscle, the internal jugular vein, the thyroid vessels and all demonstrable lymphatics are included in the dissection and are removed en bloc. Included in this dissection are the prethyroid muscles.
Thyroglossal Duct. This duct originates at
FIG. Removal of a thyroglossal duct: (A) course of a patent thyroglossal duct and cyst; (B) incision; (C) dissection to the hyoid bone; (D) cutting the hyoid bone; (E) an assistant’s finger placed in the mouth and pressing on the tongue makes the deeper part of the duct more accessible; (F) dissection completed.
an early stage in fetal life as a depression in the midline of the posterior third of the tongue which is known as the foramen caecum. From it a solid cord of cells grows downward which becomes canalized to form the duct that passes downward in the midline of the neck between the genioglossi muscles. It extends as far as the upper border of the thyroid cartilage and then turns to either side of the midline. This part of its course is represented after birth by the pyramidal lobe of the thyroid gland and a musculofibrous band connecting that lobe to the hyoid bone. Frazer seems to have settled the question as to whether the duct runs in front of, behind or through the hyoid bone. His works demonstrate that the duct passes in front of the body of the hyoid and then curves up behind the bone before again continuing downward. Therefore, it is important to remove this section of the hyoid bone when removing a patent duct. After passing the thyroid cartilage, the thyroglossal duct expands to form the thyroid gland. If the duct remains patent, a thyroglossal cyst develops. Such a cyst is found usually above the thyroid cartilage and in the midline. Hamilton Bailey has stated that if these cysts develop below the thyroid cartilage, they naturally follow the course of the duct and appear to one or the other side of the midline, usually to the left. Normally, the
FIG. The parathyroid glands. (A) Posterior view; in position one, the inferior parathyroid is below the inferior thyroid artery, but in position two, it is above the artery. The superior parathyroid in this instance is intraglandular. (B) Cross section. In position one, the gland is anterior to the pretracheal fascia; in position two, it is posterior to this fascia; and in position three, it is intraglandular.
thyroglossal duct does not open onto the surface of the skin of the neck. Therefore, a congenital thyroglossal fistula is not possible, and if a fistula does develop it must be secondary and brought about by a bursting of or an opening into a thyroglossal cyst. Since the thyroid gland develops from the thyroglossal duct, an accessory or misplaced thyroid may develop anywhere along the line of the duct. The lingual thyroids are sometimes found at the back of the tongue in the region of the foramen caecum. The term “ectopic thyroid” means thyroid tissue found in an incorrect position, thus differing from the accessory thyroid. If a thyroglossal duct swelling appears above the hyoid bone, it is necessary only to split the mylohyoid muscle along its raphe, separate the geniohyoid muscle and remove the tumors. However, if these cysts or tumors appear subhyoid, the dissection must be more radical and include removal of a portion of the hyoid bone. Thyroglossal cysts, fistulae and sinuses must be removed radically to accomplish a cure. The cyst is exposed by a transverse incision that is carried down to the sternohyoid muscles. These are divided vertically in the midline, and the cyst is dissected free to the level of the hyoid bone. To expose the sinus completely, a small portion of hyoid bone must be removed in the midline. An assistant’s finger placed in the patient’s mouth and passed over the back of the tongue enables him to push the foramen caecum and any remaining portion of the sinus tract within reach of the operator. Since the duct is small and cannot be seen clearly, it is best to dissect some of the surrounding tissue with it. Therefore, in the removal it is necessary to include some small portion of the mylohyoid, the geniohyoid and the genioglossus muscles. Deep structures are sutured; divided edges of the hyoid bone are approximated; the wound is closed with or without drainage. PARATHYROID GLANDS
The parathyroid glands are yellowish-brown bodies, the number and the position of which are variable. A superior and an inferior parathyroid are usually present on each side, occupying any position from the back of the pharynx to the superior mediastinum. They are about the size of a small pea and usually lie between the posterior aspect of the lateral lobe of the thyroid and the pretracheal lamina of pretracheal fascia. The parathyroids lie entirely or partially within the substance of the thyroid gland, this being particularly true of the superior, which are then easily removed in thyroidectomy. The anatomy of the inferior parathyroids is more complex than that of the superior, and the inferior lie in intimate relationship to the inferior thyroid arteries and veins. Their position is variable. Walton has described three rather typical positions of the parathyroids in relation to their surrounding fascial plane: (1) the gland lies below the inferior thyroid artery and is then anterior to the pretracheal fascia; (2) the gland lies above the artery and is then frequently situated deep to the pretracheal fascia and visible only upon incising the fascia; (3) the parathyroids may be in the substance of the thyroid gland proper. If a tumor develops in a parathyroid in the first-described position, it may pass between the two capsules of the thyroid, along the inferior thyroid veins, in front of the common carotid artery and finally come to lie behind the sternum. If such a tumor is situated behind the pretracheal fascia, it cannot be seen until the fascia is incised and an inspection made even around the circumference of the esophagus. It may even pass into the thorax behind the esophagus. The superior and the inferior parathyroid glands receive their blood supply from the corresponding thyroid vessels.
THYMUS GLAND
Embryologically, the thymus appears as 2 entodermal diverticula which arise one on either side of the 3rd branchial pouch. A ventral diverticulum of the 4th pouch may take part in the formation of the gland or entirely disappear. As the 2 diverticula grow they meet and become joined by connective tissue, but there is never any real fusion of thymus tissue proper. Actually, therefore, there are 2 asymmetric thymus glands a right and a left which are easily separated by blunt dissection.
The adult thymus gland is a temporary organ that is “sandwiched” between the sternum and the great vessels in the region of the superior mediastinum. It is essentially an organ of the growing period of life which undergoes gradual atrophy after puberty. From birth to puberty it grows relatively slowly; there are tremendous individual variations at any given age. At birth it ranges in weight from 2 to
FIG. The thymus gland: (A) enlarged thymus gland extending in front of the pericardium; (B) development of the thymus.
roid gland. It is soft in consistency, and its shape varies with its size and the age of the individual. In infants with short thoraces it is broad and squat, but in adults with long thoraces it is drawn out into 2 irregular flattened bands. It is of pinkish-gray color and has a lobulated surface.Anteriorly, the thymus gland is related to the sternum and the lower end of the sternothyroid muscles. In the young child, its lateral margins may be insinuated between the pleura and the upper costal cartilages. Posteriorly, it is related from below upward to the pericardium, the ascending aorta,
FIG. The cervical part of the esophagus begins opposite the inferior margin of the cricoid cartilage at the level of the body of the 6th cervic al vertebra. (Inset) Cross section at the level of the first thoracic vertebra. The trachea does not cover the esophagus completely but leaves a part of its left anterior margin exposed; this makes surgical access easier from this side.
the left innominate vein, the trachea and the inferior thyroid veins. It is surrounded by a fibrous capsule that separates it from these structures. It is connected to the thyroid by a strand of tissue called the thyrothymic ligament. The arterial supply of the thymus is received through inconstant branches derived chiefly from the internal mammary artery or its branches. Veins. These vessels are irregular and drain mainly into the internal mammary or the left innominate. Lymphatics. The gland has a profuse lymphatic drainage, and certain of the lymphatics open directly into veins without first traversing lymph glands. Occasionally, the thymus retains its infantile size in the adult and for some unknown reason does not atrophy. In such cases there is a large quantity of lymphoid tissue throughout the body, and the condition is then known as status lymphaticus.
CERVICAL PORTION OF THE ESOPHAGUS
The entire esophagus is about
SURGICAL CONSIDERATIONS
ESOPHAGEAL DlVERTICULUM Shallow and Lahey have done extensive work in this field, and the former has reported a series of cases in which 1-stage diverticulectomy has been accomplished with excellent results. A longitudinal incision is made along the anterior border of the sternocleidomastoid muscle and is carried through the skin, the superficial fascia and the superficial layer of deep cervical fascia. The sternocleidomastoid is retracted backward until the omohyoid muscle is demonstrated; this is severed at the point where it disappears beneath the sternocleidomastoid. With the omohyoid retracted, the thyroid gland is separated from the internal jugular vein and the common carotid artery. Then the thyroid gland is pulled toward the midline, and the inferior thyroid artery is exposed. This often crosses over the diverticulum or gets in the way of its dissection; hence, it is best to ligate and sever it. Since a diverticulum is a herniation of mucous membrane through muscle fibers, it should be remembered that there are two weak points in the musculature of the posterior aspect of the pharynx and the esoph-
FIG. Esophageal diverticulectomy (one stage). (A) A longitudinal incision is made along the anterior border of the sternocleidomastoid muscle. (B) The omohyoid muscle is severed, and the thyroid gland is retracted medially: the sternocleidomastoid muscle and the carotid sheath are retracted laterally. The inferior thyroid artery is exposed, ligated and severed as it crosses the diverticulum. (C) Fibers of the inferior constrictor muscle are severed, and the sac is mobilized. (D) The sac is ligated close to the pharynx. (E) Closure is effected m layers.
agus; these two points are at the level of the lower fibers of the inferior constrictor, and where the cricopharyngeal muscle diverges from the lowest fibers of the inferior constrictor. These are the two locations where diverticula are most commonly found; however, the approach is usually through the left side of the neck because the esophagus passes to the left of the vertebral bodies. Shallow has made successful use of the esophagoscope to isolate and aid in the dissection of the diverticulum which is closely bound to the longitudinally running esophagus by the enveloping fibers of the cricopharyngeal muscles. These are separated at the lowest angle of the sac, the fundus is grasped with blunt forceps, and traction is made. The remaining fibers of the cricopharyngei enveloping the diverticulum are cut. When the neck of the sac is reached, the fibers of the inferior constrictor are seen along the lower border of the neck; these must be severed to mobilize it completely. The neck of the sac is transfixed and ligated, and the sac is removed. This ligation should take place close to the pharynx. The cricopharyngeus and the inferior constrictor should be closed over the ligated and invaginated sac to prevent a recurrence of the hernia.
PHARYNX
The pharynx is a large vestibule that is common to the respiratory and the digestive tracts. It is a vertically placed musculomembranous tube that extends from the base of the skull to the cricoid cartilage where it becomes continuous with the esophagus. The 6th cervical vertebra marks its lower border posteriorly. It is about
FIG.The pharynx, viewed from behind; with 3 constrictor muscles intact.
FIG. The pharynx viewed from behind, with the 3 constrictor muscles removed.
Nasopharynx (Epipharynx). This is somewhat cube-shaped and is placed behind the cavity of the nose, above and behind the soft palate. It is part of the respiratory and not of the digestive tract. Its walls, with the exception of the soft palate, are incapable of movement; therefore, the cavity remains patent, and its form never changes. Its anterior wall is formed by the posterior apertures of the nose (choanae) through which it opens into the nasal cavities. These apertures are a pair of oblong openings that slope from the base of the skull downward and forward to the posterior border of the hard palate and are separated by the vomer. By looking through them with a postnasal mirror a view is obtained of the posterior end of the inferior and the middle conchae and the 2 lower meatuses. Each opening is about
FIG. 159. Sagittal view of the pharynx. The 3 parts of the pharynx have been subdivided.
a view is obtained of the 4 orifices that open into the nasal part of the pharynx; the middle and the superior meatuses of the nose, and the middle and the superior conchae can be brought into view and their pathology determined. The side walls and the orifices of the pharyngotympanic tubes also can be fully inspected.
Oropharynx (Mesopharynx). This is partly respiratory and partly alimentary. It is the posterior continuation of the mouth cavity that lies behind the mouth and the tongue.
The anterior wall presents the opening into the mouth, the lower portion being the pharyngeal part of the dorsum of the tongue that faces directly backward. The epiglottis, which belongs to the laryngeal part of the pharynx and is situated immediately behind the tongue, appears as a leaflike plate of cartilage enveloped in mucous membrane with its upper part standing prominently up and behind the tongue. The posterior wall is smooth and is supported y the body of the axis, which is separated from the pharynx by the prevertebral fascia.The lateral wall is formed by the interval between the palatoglossal and the palatopharyngeal arches that is occupied by the tonsils. A retropharyngeal abscess produces a swelling of the posterior pharyngeal wall that may bulge forward and obstruct the air passages during respiration.
Laryngopharynx (Hypopharynx). This is the longest of the 3 subdivisions; it lies behind the larynx and diminishes in width
FIG. The muscular coat of the pharynx (side view). The origin of the 3 constrictor muscles is along a continuous line from above downward.
from above downward. Its upper part is common to the digestive and the respiratory tracts, but its lower part, opposite thecricoid, is entirely digestive. Its anterior and posterior walls are in contact except when food is swallowed. The anterior wall is formed by the inlet of the larynx and the posterior aspect of the arytenoid and the cricoid cartilages. The posterior wall is in contact with the anterior and is supported by the bodies of the 3rd, the 4th, the 5th and the 6th cervical vertebrae. The lateral walls are supported by the posterior part of the lamina of the thyroid cartilage and present a small fossa, the piriform recess, which is bounded on its medial side by the aryepiglottic fold. The mucous membrane of this area is supplied by the internal laryngeal nerve; hence, if a crumb or a small particle of food lodges in the fossa, uncontrollable coughing results. Pharyngeal Wall. This wall presents 4 rather distinct layers: buccopharyngeal fascia, muscular, fibrous and mucous coats.
1. The buccopharyngeal fascia is a layer of fibrous tissue covering both the buccinator and the pharyngeal muscles. It also invests the constrictor muscles of the pharynx, and between it and the prevertebral fascia a loose areolar tissue is found which forms an easily distensible space in which pus may spread. This layer contains the venous plexus, which drains the pharynx and communicates with the pterygoid plexus. It enters the jugular veiear the angle of the jaw.
2. The muscle coat of the pharyngeal wall is made up of 5 paired voluntary muscles: the 3 constrictors (superior, middle and inferior) which constitute an outer circular layer, and the stylopharyngeus and the palatopharyngeus which constitute an inner longitudinal layer. The 3 constrictor muscles are incomplete
FIG. Posterior view of the pharynx. The posterior wall has been cut open to show the internal and the recurrent laryngeal nerves and the superior laryngeal artery.
in front, but each widens posteriorly and joins its fellow in the median plane at the median raphe. Each muscle is somewhat fanshaped and is attached by its front end or handle to the side wall of the nasal, the oral or the laryngeal cavity. Each partly overlaps externally the muscle above it, so that the inferior overlaps the middle, and the middle overlaps the superior. The origin of these muscles is continuous from above down. The superior constrictor originates from the lower third of the posterior border of the medial pterygoid plate, the pterygomandibular ligament, the side of the tongue, the mucous
FIG. The larynx; 4 views and a disarticulated larynx are shown.
membrane of the mouth and the mylohyoid line. The middle constrictor originates from the stylohyoid ligament and the hyoid bone. The inferior constrictor arises from the oblique line of the thyroid cartilage and the fascia covering the cricothyroid muscle. They are inserted into a median raphe situated posteriorly, and all are supplied by the pharyngeal plexus through the accessory part of the spinal accessory nerve. The inferior constrictor receives 2 additional nerves: the external and the recurrent laryngeal branches of the vagus. The stylopharyngeus muscle enters the wall of the pharynx between the superior and the middle constrictors. Itmeets the palatopharyngeus muscle and is inserted with it into the posterior border of the thyroid cartilage. This is visible only after cutting the inferior constrictor muscle. The stylopharyngeus is supplied by the glossopharyngeal nerve, and the palatopharyngeus by the accessory nerve.
3. The fibrous coat has been called the pharyngobasilar fascia, the pharyngeal aponeurosis and also the submucous coat. It is strong in its upper part and takes the place of muscle tissue where the superior constrictor is absent. As it passes downward it gradually becomes weaker until it is finally lost as a distinct layer. It forms the principal attachment between the pharynx and the base of the skull.
4. The mucous coat consists of a columnar, ciliated epithelium in the nasopharynxand stratified squamous in the lower part. The various structures pass in a definite arrangement between the constrictor muscles. Between the base of the skull and thesuperior constrictor are the tensor palati, the pharyngotympanic tube and the levator palati. Between the superior and the middleconstrictors are the stylopharyngeus muscle and the glossopharyngeal nerve. Between the middle and the inferior constrictors are the internal laryngeal nerve and the superior laryngeal artery. Between the inferior constrictor and the esophagus are the recurrent laryngeal nerve and the inferior laryngeal artery.
LARYNX
This upper and specialized portion of the windpipe extends from the epiglottis to the cricoid; it forms the organof the voice. At birth it lies opposite the 3rd and the 4th cervical vertebrae but gradually descends until in the adult, it lies opposite the 3rd, the 4th, the 5th and the 6th cervical vertebrae. It is situated in thefront and upper part of the neck, below the tongue and the hyoid bone, and between the great vessels of the neck. Above, it opens into the pharynx and below into the trachea. In the midline, it is covered by skin and cervical fascia but laterally is overlaid by the sternohyoid, the sternothyroid, the thyrohyoid and the origin of the inferior constrictor muscles. It consists of cartilages, ligaments and muscles and is lined by mucous membrane. Laterally, it is embraced by the lateral lobes of the thyroid gland, above which it is related to the carotid sheaths. Behind, it rests upon the pharynx which separates it from the body of the 3rd to the 6th cervical vertebrae. After puberty, the larynx is smaller in the female than in the male, the vocal cords in the former being about two thirds the length of the latter.
Cartilages of the Larynx. These are
Muscles. The muscles of the larynx are extrinsic and intrinsic. The extrinsic muscles have been described elsewhere; they act upon the voice box as a whole. They are the omohyoid, the sternohyoid, the sternothyroid, the thyrohyoid and certain suprahyoid muscles (stylopharyngeus, palatopharyngeus, inferior and middle constrictors of the pharynx). The intrinsic muscles, on the other hand, confine themselves entirely to the larynx and act on its parts to modify the size of the laryngeal aperture (rima glottidis) and also control the degree of tension of the vocal ligaments. The principal intrinsic laryngeal muscles are the cricothyroid, the arytenoids (transverse and oblique), the posterior cricoarytenoids, the lateral cricoarytenoid and the thyroarytenoid. All of these, with the exception of the transverse arytenoid, are in pairs.
The cricothyroid muscle is the only intrinsic muscle that lies on the exterior of the larynx. It arises from the lateral surface of
FIG. The intrinsic muscles of the larynx; 4 views are shown
the cricoid, runs upward and backward and is inserted into the inferior horn of the thyroid cartilage. It bridges the lateral portion of the cricothyroid interval. The cricothyroid muscles are the chief tensors of the vocal ligaments; this action is accomplished by pulling the arch of the cricoid upward around its articulation with the inferior horn of the thyroid cartilage, thus forcing the arytenoids backward and stretching the vocal cords. The posterior cricoarytenoid is probably the most important of the laryngeal muscles,since its action separates (abducts) the vocal cords, thus widening the rima glottidis. All the other muscles close the larynx by a more or less sphincteric (adduction) action. The cricoarytenoid arises from the back of the cricoid, runs upward and outward to the muscular process of the arytenoid where it inserts. By pulling backward on this process the vocal cords are separated. Bilateral abductor paralysis of these muscles results in suffocation. When both recurrent laryngeal nerves are injured, bilateral abductor paralysis results, and the vocal cords become lax and cannot be abducted. At first this rarely results in dyspnea, but the loss of
FIG. The action of the intrinsic muscles of the larynx. (A) The action of the posterior cricoarytenoid muscles, separating the vocal cords. (B) By the contraction of the cricothyroid muscle, the vocal ligaments are tensed. (C) Adduction of the vocal cords is brought about by the contraction of the oblique and transverse arytenoids muscles.
voice is immediate. Within 3 to 5 months the voice begins to improve but, unfortunately, dyspnea also makes its appearance. This is the result of atrophy and fibrosis. Within a few weeks the voice becomes more improved, but as the vocal cords continue to fibrose and gradually approach each other the dyspnea becomes severe, especially on exertion. The laryngoscope will reveal the presence of a mere slit. The transverse arytenoid is the only unpaired muscle of the larynx. It is a thin, flat, muscular band passing from the back of one arytenoid cartilage to the other. When it contracts, it draws the posterior parts of the arytenoids together, helping to close the laryngeal inlet during swallowing. The oblique arytenoid muscles are a pair of weak muscular slips that lie on the back of the transverse muscle and cross each other, forming a letter X. This muscle continues on as the aryepiglotticus in the aryepiglottic fold in which it reaches the epiglottis. Its action draws the arytenoids together and shortens the aryepiglottic fold. This approximates the arytenoids and the epiglottis. The muscle acts as a sphincter for the laryngeal inlet during swallowing. The lateral cricoarytenoid muscle arises from the upper aspect of the lateral part of the cricoid, runs upward and backward and is inserted into the muscular process of the arytenoid. These muscles are adductors of the vocal cords and reduce the width of the rima glottidis. The thyroarytenoid is an upward continuation of the lateral cricoarytenoid. It arises from the deep surface of the thyroid lamina, passes backward and inserts into the anterolateral surface of the arytenoid cartilage. It pulls the arytenoid cartilage forward and slackens the vocal folds. The uppermost fibers of this muscle curve upward into the aryepiglottic fold, are called the thyroepiglottic muscles and join with the aryepiglottic muscles to insert in the edge of the epiglottis. Some of the deepest fibers of the thyroarytenoid form a muscle bundle, the vocal muscle; this cannot be separated from the rest of the muscle and actually is the inner constant part that lies in the vocal lip lateral to the vocal ligament. It draws the vocal process forward, relaxing the vocal ligaments. The action of the laryngeal muscles is threefold: (1) they open the glottis and permit breathing; (2) they close the glottis and the vestibule during swallowing; (3) they regulate the tension of the vocal cords. The first two actions are automatic and are controlled by the medulla, but the third is voluntary and is controlled by the cerebral cortex. The posterior cricoarytenoids are the only abductors. The lateral cricoarytenoids adduct the cords. The muscles that close the vestibule are the thyroarytenoid, the aryepiglottic and the thyroepiglottic. The muscles that effect the tension of the cords are the cricothyroid, the vocalis and the thyroarytenoid.
Nerves of the Larynx. The nerve supply is derived from the vagus nerve by way of its 2 branches, the superior and the inferior (recurrent) laryngeal, both of which are mixed nerves. After a short course, the superior laryngealnerve divides into a thin external and a stouter internal branch. The external laryngeal nerve is applied to the inferior constrictor muscle and passes deeply to the insertion of the sternothyroid. In its course it passes to and is accompanied by the superior thyroid artery; it sends a few twigs to the inferior constrictor, pierces it and ends by supplying the cricothyroid muscle. The internal laryngeal nerve is sensory and pierces the thyrohyoid membrane as several diverging branches. It crosses the anterior wall of the piriform recess and supplies sensory fibers to the larynx above the vocal cords. Nordland and other investigators believe that this nerve innervates the interarytenoid muscle in most cases. Division of the superior laryngeal nerves results in a loss of sensation to the laryngeal mucous membrane, making it difficult or impossible for the patient to perceive a foreign body in the larynx. There is also a weakening or paralysis of the cricothyroid, which produces a huskiness of the voice. The inferior (recurrent) laryngeal nerve arises at different levels on the 2 sides. On the right it arises in the root of the neck and winds around the subclavian artery, but on the left it arises in the superior mediastinum and winds around the arch of the aorta. It ascends anterior to the tracheo-esophageal groove and can be felt on the lateral aspect of the trachea. It continues upward and becomes intralaryngeal by passing deep to the lower border of the inferior constrictor muscle. The point at which this nerve becomes intralaryngeal is on a level with the inferior horn of the thyroid cartilage.
Vascular Supply of the Larynx. This is derived from the superior laryngeal branch of the superior thyroid artery and the inferior laryngeal branch of the inferior thyroid artery.
Lymphatics. The lymphatics from the upper part end in glands in the carotid triangle, and from the lower part in the glands in front of and besides the larynx and the trachea.
Cavity of the Larynx. This may be divided into 3 compartments: vestibule (supraglottic), middle compartment (glottic area) and an infraglottic area. Some authors have likened the superior aperture of the larynx to a triangle, the base of which is at the
FIG. The inlet of the larynx as seen through a laryngeal mirror. The inset shows the structures magnified and identified.
epiglottis, the sides formed by the arytenoepiglottic folds, and the apex located at the arytenoid commissure posteriorly.
Inlet of the Larynx. The inlet, or upper aperture, faces almost directly backward so that it is set at right angles to the long axis of the laryngeal tube. It is bounded above by the free margin of the epiglottis, on either side by the aryepiglottic folds of mucous membrane which stretch from the epiglottis to the arytenoid cartilage,
FIG. Thyrotomy, laryngotomy and tracheotomy incisions.
and below by which covers the posterior aspect of the epiglottis. Its central point is marked by a rounded elevation, the tubercle of the epiglottis, which is important because it is the most noticeable feature on laryngoscopic examination and is frequently the only structurethat is visible in the hands of a novice. The aryepiglottic folds contain the aryepiglottic muscles between its two layers of mucous membrane. Posteriorly, the vestibule is bounded by the arytenoid cartilages and the interarytenoid fold containing the transverse arytenoid muscle. The aryepiglottic and transverse arytenoid muscles are of great importancebecause they close the inlet of the larynx during the act of swallowing. The vestibular fold of mucous membrane passes backward and laterally from the thyroid angle. It contains a small fibrous band, the vestibular ligament (false vocal cord), which stretches from the thyroid angle to the arytenoids cartilage. This fold narrows the lower end of the vestibule.
Glottis. The glottis, or middle compartment, is the narrowest part of the interior of the larynx; it measures nearly
Vocal Cords. The true vocal cords diverge as they pass posteriorly and extend from the vocal process of the arytenoid to the thyroid angle. They appear as short straight folds that are characterized by the pallor of the covering mucous membrane. This pallor is produced by the absence of loose submucous tissue as well as the absence of blood vessels. The rima glottidis {glottic slit) is that fissure which separates the true vocal cords and the arytenoid cartilages; it is triangular when at rest, linear during phonation and lozenge-shaped in respiration. The glottis is closed after inspiration, thus aiding fixation of the diaphragm during efforts of expulsion (parturition, defecation, urination and vomiting) .The infraglottic, or lowest compartment of the larynx, extends from the true vocal cords to the first tracheal ring. Its walls are made up of the thyroid and the cricoid cartilages and the cricothyroid membrane. In emergency laryngotomy this membrane is incised to gain entrance into the larynx.
SURGICAL CONSIDERATIONS
Thyrotomy (Laryngofissure). The incision extends from the hyoid bone above to the cricoid cartilage below; it is placed exactly in the midline and deepened until the isthmus of the thyroid gland is exposed. If necessary, this is divided. When the thyroid cartilage is visualized, a vertical incision is made in the midline through it and the thyrohyoid membrane. Through this incision tumors of the larynx can be removed and treated when removal of the entire larynx is unnecessary. At times this operation also has been used for the removal of foreign bodies that could not be dislodged by other means. The two segments of thyroid cartilage and membranes are sutured together. Some authorities permit the divided cartilage to fall together without suturing.
Laryngotomy has been used as an emergency procedure when the presence of a foreign body or edema necessitates the rapid admission of air into the larynx. It has also been used as a preliminary step in extensive operative procedures. A cyanosed and almost asphyxiated patient can be relieved immediately by this operation, in which a transverse incision is made across the midline of the neck at the level of the upper border of the cricoid cartilage. If the incision is kept close to the upper border, the cricothyroid artery will be avoided. Then it is deepened to and through the cricothyroid membrane, and a laryngotomy tube is inserted. It should be remembered that the cricothyroid space, in children, is so small that it is usually unsuitable for this operation. In extreme emergencies where death from asphyxia appears imminent, the blade of a pocket knife has been successfully plunged directly through the cricothyroid membrane and the opening kept patent by rotating the handle of the knife.
Tracheotomy (tracheostomy) may be an elective or emergency procedure. If elective, it is usually a preliminary step to laryngectomy for malignant disease. However, if it is done as an emergency operation it is utilized where there has been sudden obstruction of the airway as a result of aspiration of a foreign body, edema of the larynx, infections and edema about the throat, or postoperative vocal cord paralysis following injury to both recurrent nerves. Distinction has been made between low and high tracheotomy, the low being below the isthmus of the thyroid and the high above it. Most authorities are of the opinion that the low operation is preferable. Here an
FIG. Tracheostomy
incision is made extending from the lower border of the thyroid cartilage downward for about
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.
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7. Philip Thorek. Anatomy In Surgery /J.B.Lippincott Company/,1996.-935p.
