Lesson 5
Muscles
of the back
Muscles of the thorax and
abdomen
MUSCLES
OF THE UPPER EXTREMITY
MUSCLES
OF THE LOWER EXTREMITY
Muscles of the back subdivide into
superficial and deep (proper) groups.
1.
Trapezius
· Origin:
1. external occipital protuberance
2. along the medial sides of the superior nuchal line
3. ligamentum nuchae (surrounding the
cervical spinous processes)
4. spinous processes of C1-T12
· Insertion:
1. posterior, lateral 1/3 of clavicle
2. acromion
3. superior spine of scapula
· Action:
1. elevates scapula
2. upward rotation of the scapula (upper
fibers)
3. downward rotation of the scapula (lower
fibers)
4. retracts scapula
· Blood: transverse cervical artery
· Nerve:
1. spinal Accessory (XI) (efferent or motor
fibers)
2. ventral ramii of C3 & C4 (afferent
or sensory fibers)
2.
Latissimus dorsi
· Origin:
1. spinous process of T7-L5
2. upper 2-3 sacral segments
3. iliac crest
4. lower 3 or 4 Ribs
· Insertion: lateral lip of the intertubercular groove
· Action:
1. adduction of humerus
2. medial rotation of the humerus
3. extension from flexed position
4. downward rotation of the scapula
· Blood: thoracodorsal artery
· Nerve: thoracodorsal nerve, C6,7,8
3.
Rhomboid major
· Origin:
1. spinous processes of T2-T5
2. supraspinous ligament
· Insertion: medial scapula from the scapular spine to the
inferior angle
· Action: retract scapula
· Blood:
1. deep branch of transverse cervical
artery, OR
2. dorsal scapular artery
· Nerve: dorsal scapular nerve, C5
4.
Rhomboid minor
· Origin:
1. spinous process of C7 & T1
2. ligamentum nuchae
3. supraspinous ligament
· Insertion: medial margin of the scapula at the medial angle
· Action: retract scapula
· Blood:
1. deep branch of transverse cervical
artery, OR
2. dorsal scapular artery
· Nerve: dorsal scapular nerve, C5, [C4]
5.
Levator scapulae
· Origin: transverse processes of C1-C3 or C4
· Insertion: superior angle of scapula toward the scapular spine
· Action:
1. elevates the scapula
2. extends and/or laterally flexes the head
· Blood: transverse cervical artery
· Nerve:
1. nerves off cervical plexus, C3,4
2. dorsal scapular nerve, C5
6.
Serratus posterior superior
· Origin: vertebrae C7-Th2
· Insertion: 2-5 ribs
· Action:
1. elevates ribs
· Blood:
1. posterior intercostal art., deep
cervical artery upper part
· Nerve: intercostal nernes, Th1-Th4
7.
Serratus posterior inferior
· Origin: vertebrae Th11-L2
· Insertion: 8 - 12 ribs
· Action:
1. depresses the ribs
· Blood: posterior intercostal arteries
· Nerve: intercostal nernes, Th9-Th12
1.
Splenius capitis
· Origin:
1. lower portion of ligamentum nuchae
2. spinous processes of C3-T3(4)
· Insertion:
1. superior nuchal line
2. mastoid process of temporal bone
· Action:
1. bilateral contraction: extend head &
neck
2. unilateral contraction: rotate and
laterally bend head & neck to the contracted (same) side
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
2.
Splenius cervicis
· Origin: spinous process of T3-T6
· Insertion: posterior tubercles of transverse processes of C2-C4
· Action:
1. bilateral contraction: extend head &
neck
2. unilateral contraction: rotate and
laterally bend head & neck to the contracted (same) side
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Iliocostalis lumborum
· Origin: common tendinous origin: (same for all lower erector
spinae)
1. sacrum
2. iliac crest
3. spinous processes of lower thoracic
& most lumbar vertebrae
· Insertion: lower border of angles of ribs (5)6-12
· Action: (same for all
erector spinae)
1. bilateral:
a. extension of vertebral column
b. maintenance of erect posture
c. stabilization of vertebral column during flexion,
acting in contrast to abdominal muscles and the action of gravity
2. unilateral:
a. lateral bend to same side
b. rotation to same side
c. opposite muscles contract eccentrically for
stabilization
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Iliocostalis thoracis
· Origin: upper border of ribs 6-12 (medial to
· Insertion: lower border of angles of ribs 1-6 (sometimes
transverse process of C7)
· Action: (same for all erector spinae)
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Iliocostalis cervicis
· Origin: angles of ribs 1-6
· Insertion: transverse processes of C4-C6
· Action: (same for all erector spinae)
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Longissimus
thoracis
· Origin: common tendinous origin: (same for all lower erector
spinae)
1. sacrum
2. iliac crest
3. spinous processes of lower thoracic & most lumbar vertebrae
· Insertion:
1. transverse processes of all thoracic vertebrae
2. all ribs between tubercles and angles
3. transverse processes of upper lumbar vertebrae
· Action: (same for all erector spinae)
1. bilateral:
a. extension of vertebral column
b. maintenance of erect posture (pneumonic = I Like Standing)
c. stabilization of vertebral column during flexion, acting in
contrast to abdominal muscles and the action of gravity
2. unilateral:
a. lateral bend to same side
b. rotation to same side
c. opposite muscles contract eccentrically for stabilization
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Longissimus
cervicis
· Origin: transverse processes of T1-T5(6)
· Insertion: transverse processes of C2-C6
· Action: (same for all erector spinae)
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Longissimus
capitis
· Origin:
1. transverse and articular processes of middle and lower cervical
vertebrae
2. transverse processes of upper thoracic vertebrae
· Insertion: posterior aspect of mastoid process of temporal bone
· Action: (same for all erector spinae)
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Spinalis
thoracis
· Origin: common tendinous origin: (same for all lower erector
spinae)
1. sacrum
2. iliac crest
3. spinous processes of lower thoracic & most lumbar vertebrae
· Insertion: spinous processes T3(4)-T8(9)
· Action: (same for all erector spinae)
1. bilateral:
a. extension of vertebral column
b. maintenance of erect posture (pneumonic = I Like Standing)
c. stabilization of vertebral column during flexion, acting in
contrast to abdominal muscles and the action of gravity
2. unilateral:
a. lateral bend to same side
b. rotation to same side
c. opposite muscles contract eccentrically for stabilization
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Spinalis
cervicis
· Origin: spinous processes of C6-T2
· Insertion: spinous processes of C2 (and possibly extend to C3
or C4)
· Action: (same for all erector spinae)
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Spinalis
capitis
· Origin: spinous processes of lower cervical & upper
thoracic vertebrae
· Insertion: between superior & inferior nuchal lines of
occipital bone
· Action: (same for all erector spinae)
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Semispinalis
thoracis
· Origin: transverse processes of T6-T12 vertebrae
· Insertion: spinous processes of upper thoracic & lower
cervical vertebrae
· Action:
1. bilaterally extends vertebral column, especially head and neck
2. controls lateral flexion to side opposite contraction (eccentric
for stability)
3. maintains head posture
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Semispinalis
cervicis
· Origin: transverse processes of T1-T6 vertebrae and can go down
to lower thoracic
· Insertion: spinous processes of C2-T5(6)
· Action:
1. bilaterally extends vertebral column, especially head and neck
2. controls lateral flexion to side opposite contraction (eccentric
for stability)
3. maintains head posture
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Semispinalis
capitus
· Origin:
1. transverse processes of T1-T6
2. articular processes of C4-C7
· Insertion: between superior & inferior nuchal lines of
occipital bone
· Action:
1. bilaterally extends vertebral column, especially head and neck
2. controls lateral flexion to side opposite contraction (eccentric
for stability)
3. maintains head posture
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Multifidus
· Origin:
·
cervical region: from articular
processes of lower cervical vertebrae
·
thoracic region: from transverse
processes of all thoracic vertebrae
·
lumbar region:
1. lower portion of dorsal sacrum
2. PSIS
3. deep surface of tendenous origin of erector spinae
4. mamillary processes of all lumbar vertebrae
· Insertion: spinous process of all vertebrae extending from L5 -
C2 (skipping 1-3 segments)
· Action:
1. bilaterally
extends vertebral column
2. controls
lateral flexion to side opposite contraction (eccentric for stability)
3. unilaterally
rotate vertebral bodies (column) to opposite side
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Long
rotators
· Origin: transverse process of one vertebra
· Insertion: skips one vertebra to insert on the base of spinous
process of vertebra above
· Action:
1. rotate to opposite side
2. bilateral extension
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
Short
rotators
· Origin: transverse process of one vertebra
· Insertion: base of spinous process of vertebra immediately
above
· Action:
1. rotate to opposite side
2. bilateral extension
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
5.
Interspinalis
· Origin: spinous processes of each vertebra
· Insertion: to the spinous process of vertebra immediately above
· Action: extension of the vertebrae segments
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
6.
Intertransversi
· Origin: (A to A and B to B)
·
cervical region:
A. from
the anterior tubercle of transverse process
B. from
the posterior tubercle of transverse process
·
thoracic region: (poorly developed)
·
lumbar region:
A. lateral
aspect of the transverse process
B. mamillary
process
· Insertion:
·
cervical region:
·
to the anterior tubercle immediately
above
·
to the posterior tubercle immediately
above
·
thoracic region: (poorly developed)
·
lumber region:
·
lateral aspect of the transverse
process immediately above
B. to the accessory process on the vertebra immediately above
· Action:
1. laterally
flexes each respective pair of vertebrae
2. (also
eccentric muscle contraction provides stability)
· Blood: muscular branches of the aorta
· Nerve: dorsal rami of spinal nerves
7. Levators costarum (short
and long)
· Origin: cervical and thoracic vertebrae
· Insertion: ribs
· Action: elevates ribs
· Blood: posterior intercostal artaries
· Nerve: intercostal nernes,
C8 - Th1-Th10
8. Suboccipital Musculature
Obliquus capitis inferior
• Origin: spinous process of axis (C2) • Insertion: transverse process
of atlas (C1) • Action: rotates the head to the contracted side • Blood:
muscular branches of vertebral artery • Nerve: suboccipital nerve, (dorsal rami
C1)
Obliquus capitis superior
• Origin: transverse process of atlas (C1) • Insertion: between superior
and inferior nuchal line of occiput
• Action: 1.bilaterally extends the head 2.laterally flexes to the
contracted side
• Blood: muscular branches of vertebral artery • Nerve: suboccipital
nerve, (dorsal rami C1)
Rectus capitis posterior major
• Origin: spinous process of axis (C2) • Insertion: inferior nuchal line
(lateral to minor) • Action:
1.bilaterally extends the head 2.rotates the head to the contracted side
• Blood: muscular branches of vertebral artery • Nerve: suboccipital
nerve, (dorsal rami C1)
Rectus capitis posterior minor • Origin: posterior tubercle of atlas
(C1) • Insertion: inferior nuchal line (adjacent to midline) • Action:
bilaterally extends the head • Blood: muscular branches of vertebral artery •
Nerve: suboccipital nerve, (dorsal rami C1)
They differ some regions in back: vertebral region, sacral region,
scapular region, subscapular region, and lumbar region.
Thoracic region. THE MUSCLES
OF THE Thorax. Diaphragm
Muscles
of the thorax subdivide into superficial and proper (deep)
groups.
Pectoral
Musculature
1.
Pectoralis major
· Origin:
1. medial
1/3 of clavicle
2. anterior
aspect of manubrium & length of body of sternum
3. cartilaginous
attachments of upper 6 ribs
4. external
oblique's aponeurosis
· Insertion:
1. lateral
lip of bicipital groove to the crest of the greater tubercle
2. clavicular
fibers insert more distally; sternal fibers more proximally
· Action:
1. adducts
humerus
2. medially
rotates humerus
3. flexion
of the arm from extension (clavicular portion)
· Blood:
1. pectoralis
branch of thoracoacromial artery (runs with lateral pec. nerve)
2. lateral
thoracic artery (lesser supply, and runs with medial pectoral nerve)
· Nerve:
1. lateral
pectoral nerve, C5,6,7 to clavicular portion
2. medial
pectoral nerve, C8,T1 to sternal portion
2.
Pectoralis minor
· Origin:
outer surface of ribs 2-5 or 3-5 or 6
· Insertion:
medial aspect of coracoid process of the scapula
· Action:
1. depresses
& downwardly rotates the scapula
2. assists
in scapular protraction from a retracted position
3. stabilizes
the scapula
· Blood:
lateral thoracic artery
· Nerve:
medial pectoral nerve, C8,T1
3.
Subclavius · Origin:
first rib about the junction of bone and cartilage
· Insertion:
lower surface of clavicle
· Action:
assists in stabilizing the clavicle
· Blood:
clavicular branch of thoracoacromial artery
· Nerve:
nerve to the subclavius, C5,6
4.
Serratus anterior
· Origin:
fleshy slips from the outer surface of upper 8 or 9 ribs
· Insertion:
costal aspect of medial margin of the scapula
· Action:
1. protract
scapula
2. stabilize
scapula
3. assists
in upward rotation
· Blood:
1. lateral
thoracic artery supplies the upper part
2. thoracodorsal
artery supplies the lower part
· Nerve: long thoracic nerve,
C5,6,7
Follow muscles belong to Proper (deep) group of the thorax:
1.
External intercostal muscles elevate
the ribs
2.
Internal intercostal muscles lower
ribs
3.
Subcostal muscles lower the ribs
4.
Transversus thoracis muscles lower
the ribs
5.
Levators costarum (short and long).
They originatefrom cervical and thoracic vertebrae, inserte to ribs. Action:
elevates ribs.
Diaphragm -
muscular and tendon organ that separates thoracic and abdominal cavities. It
has muscular portion and the tendon. Muscular part is divided into three parts:
sternal part, costal and lumbar parts. There are weak places where diaphragmatic
hernia can be happen – lubocostal and
sternocostal tringles. The diaphragm
is the dome-shaped sheet of muscle that separates the chest from the abdomen.
It is attached to the spine, ribs and sternum and plays a very important role
in the breathing process. The lungs are enclosed in a kind of cage in which the
ribs form the sides and the diaphragm, an upwardly arching sheet of muscle,
forms the floor. When we breathe, the diaphragm is drawn downward until it is
flat. At the same time, the muscles around the ribs pull them up like a hoop
skirt. The chest cavity becomes deeper and larger, making more air space. The
muscle fibers of the diaphragm converge on the central tendon, which is a thick, flat plate of dense fibers. There
are openings in the diaphragm for the esophagus (esophageal hiatus), the phrenic nerve (which controls the
movements of the diaphragm to produce breathing), and the aorta (aortic hiatus) and vena cava blood
vessels (foramen venae cavae inferioris),
which lead to and from the heart. When air is drawn into the lungs, the muscles
in the diaphragm contract, pulling the central tendon down. This enlarges the
chest, and air then passes into the lungs to fill the larger space. The
diaphragm sometimes contracts involuntarily because the controlling nerves are
irritated by eating too fast (or for some other reason). At this time, if air
is inhaled, the space between the vocal cords at the back of the throat close
suddenly, producing the clicking noise we call "hiccups."
Breathing
The diaphragm contracts and
moves downward elongating the thoracic cavity while the external intercostal muscles contract widening the thoracic cavity
causing air to fill the lungs through suction (inspiration). The diaphragm and external intercostal then
relax, decreasing the thorax size and reducing lung capacity forcing air out of
the lungs (expiration).
THE REGIONS OF THE ABDOMEN.
THE MUSCLES OF THE ABDOMEN
The muscles of the abdomen may be divided into two groups: (1) the anterolateral
muscles; (2) the posterior muscles.
1. the Antero-lateral Muscles of the Abdomen—The
muscles of this group are:
Obliquus externus.
Transversus.
Obliquus internus.
Rectus.
Pyramidalis.
The Obliquus externus abdominis.
The Obliquus externus abdominis (External or descending
oblique muscle) situated on the
lateral and anterior parts of the abdomen, is the largest and the most
superficial of the three flat muscles in this region. It is broad, thin, and
irregularly quadrilateral, its muscular portion occupying the side, its
aponeurosis the anterior wall of the abdomen. It arises, by eight fleshy
digitations, from the external surfaces and inferior borders of the lower eight
ribs; these digitations are arranged in an oblique line which runs downward and
backward, the upper ones being attached close to the cartilages of the
corresponding ribs, the lowest to the apex of the cartilage of the last rib,
the intermediate ones to the ribs at some distance from their cartilages. The
five superior serrations increase in size from above downward, and are received
between corresponding processes of the Serratus anterior; the three lower ones
diminish in size from above downward and receive between them corresponding
processes from the Latissimus dorsi. From these attachments the fleshy fibers
proceed in various directions. Those from the lowest ribs pass nearly
vertically downward, and are inserted into the anterior half of the outer lip
of the iliac crest; the middle and upper fibers, directed downward and forward,
end in an aponeurosis, opposite a line drawn from the prominence of the ninth
costal cartilage to the anterior superior iliac spine.
The aponeurosis of the Obliquus externus abdominis is
a thin but strong membranous structure, the fibers of which are directed
downward and medialward. It is joined with that of the opposite muscle along
the middle line, and covers the whole of the front of the abdomen; above,
it is covered by and gives origin to the lower fibers of the Pectoralis major; below,
its fibers are closely aggregated together, and extend obliquely across from
the anterior superior iliac spine to the public tubercle and the pectineal
line. In the middle line, it interlaces with the aponeurosis of the opposite
muscle, forming the linea alba, which extends from the xiphoid process
to the symphysis pubis.
That portion of the aponeurosis which extends between the
anterior superior iliac spine and the pubic tubercle is a thick band, folded
inward, and continuous below with the fascia lata; it is called the inguinal
ligament. The portion which is reflected from the inguinal ligament at the
pubic tubercle is attached to the pectineal line and is called the lacunar
ligament. From the point of attachment of the latter to the pectineal line,
a few fibers pass upward and medialward, behind the medial crus of the
subcutaneous inguinal ring, to the linea alba; they diverge as they ascend, and
form a thin triangular fibrous band which is called the reflected inguinal
ligament.
In the aponeurosis of the Obliquus externus, immediately
above the crest of the pubis, is a triangular opening, the subcutaneous
inguinal ring, formed by a separation of the fibers of the aponeurosis in
this situation.
The following structures require further description, viz.,
the subcutaneous inguinal ring, the intercrural fibers and fascia,
and the inguinal, lacunar, and reflected inguinal ligaments.
Variations.—The Obliquus externus
may show decrease or doubling of its attachments to the ribs; addition slips
from lumbar aponeurosis; doubling between lower ribs and ilium or inguinal
ligament. Rarely tendinous inscriptions occur.
The Obliquus internus abdominis (Internal or
ascending oblique muscle) thinner and smaller than the Obliquus externus,
beneath which it lies, is of an irregularly quadrilateral form, and situated at
the lateral and anterior parts of the abdomen. It arises, by fleshy
fibers, from the lateral half of the grooved upper surface of the inguinal
ligament, from the anterior two-thirds of the middle lip of the iliac crest, and
from the posterior lamella of the lumbodorsal fascia. From this origin the
fibers diverge; those from the inguinal ligament, few in number and paler in
color than the rest, arch downward and medialward across the spermatic cord in
the male and the round ligament of the uterus in the female, and, becoming
tendinous, are inserted, conjointly with those of the Transversus, into
the crest of the pubis and medial part of the pectineal line behind the lacunar
ligament, forming what is known as the inguinal aponeurotic falx. Those
from the anterior third of the iliac origin are horizontal in their direction,
and, becoming tendinous along the lower fourth of the linea semilunaris, pass
in front of the Rectus abdominis to be inserted into the linea alba. Those arising
from the middle third of the iliac origin run obliquely upward and medialward,
and end in an aponeurosis; this divides at the lateral border of the Rectus
into two lamellæ, which are continued forward, one in front of and the
other behind this muscle, to the linea alba: the posterior lamella has an
attachment to the cartilages of the seventh, eighth, and ninth ribs. The most
posterior fibers pass almost vertically upward, to be inserted into the
inferior borders of the cartilages of the three lower ribs, being continuous
with the Intercostales interni.
The Obliquus internus abdominis.
Variations.—Occasionally,
tendinous inscriptions occur from the tips of the tenth or eleventh cartilages
or even from the ninth; an additional slip to the ninth cartilage is sometimes
found; separation between iliac and inguinal parts may occur.
The Cremaster is a thin muscular layer, composed of a number of fasciculi which arise
from the middle of the inguinal ligament where its fibers are continuous with
those of the Obliquus internus and also occasionally with the Transversus. It
passes along the lateral side of the spermatic cord, descends with it through
the subcutaneous inguinal ring upon the front and sides of the cord, and forms
a series of loops which differ in thickness and length in different subjects.
At the upper part of the cord the loops are short, but they become in
succession longer and longer, the longest reaching down as low as the testis,
where a few are inserted into the tunica vaginalis. These loops are united
together by areolar tissue, and form a thin covering over the cord and testis,
the cremasteric fascia. The fibers ascend along the medial side of the
cord, and are inserted by a small pointed tendon into the tubercle and crest of
the pubis and into the front of the sheath of the Rectus abdominis.
The Cremaster.
The Transversus abdominis (Transversalis muscle)
so called from the direction of its fibers, is the most internal of the flat
muscles of the abdomen, being placed immediately beneath the Obliquus internus.
It arises, by fleshy fibers, from the lateral third of the inguinal
ligament, from the anterior three-fourths of the inner lip of the iliac crest,
from the inner surfaces of the cartilages of the lower six ribs, interdigitating
with the diaphragm, and from the lumbodorsal fascia. The muscle ends in front
in a broad aponeurosis, the lower fibers of which curve downward and
medialward, and are inserted, together with those of the Obliquus
internus, into the crest of the pubis and pectineal line, forming the inguinal
aponeurotic falx. Throughout the rest of its extent the aponeurosis passes
horizontally to the middle line, and is inserted into the linea alba; its upper
three-fourths lie behind the Rectus and blend with the posterior lamella of the
aponeurosis of the Obliquus internus; its lower fourth is in front of the
Rectus.
Variations.—It may be more or less
fused with the Obliquus internus or absent. The spermatic cord may pierce its
lower border. Slender muscle slips from the ileopectineal line to transversalis
fascia, the aponeurosis of the Transversus abdominis or the outer end of the
linea semicircularis and other slender slips are occasionally found.
The inguinal aponeurotic falx (falx aponeurotica
inguinalis; conjoined tendon of Internal oblique and Transversalis muscle)
of the Obliquus internus and Transversus is mainly formed by the lower part of
the tendon of the Transversus, and is inserted into the crest of the pubis and
pectineal line immediately behind the subcutaneous inguinal ring, serving to
protect what would otherwise be aweak point in the abdominal wall. Lateral to
the falx is a ligamentous band connected with the lower margin of the
Transversus and extending down in front of the inferior epigastric artery to
the superior ramus of the pubis; it is termed the interfoveolar ligament of
Hesselbach and sometimes contains a few muscular fibers.
The Transversus abdominis, Rectus abdominis, and Pyramidalis.
The Rectus abdominis is a long flat muscle, which extends
along the whole length of the front of the abdomen, and is separated from its
fellow of the opposite side by the linea alba. It is much broader, but thinner,
above than below, and arises by two tendons; the lateral or larger is
attached to the crest of the pubis, the medial interlaces with its fellow of
the opposite side, and is connected with the ligaments covering the front of
the symphysis pubis. The muscle is inserted by three portions of unequal
size into the cartilages of the fifth, sixth, and seventh ribs. The upper
portion, attached principally to the cartilage of the fifth rib, usually has
some fibers of insertion into the anterior extremity of the rib itself. Some
fibers are occasionally connected with the costoxiphoid ligaments, and the side
of the xiphoid process.
The Rectus is crossed by fibrous bands, three in number,
which are named the tendinous inscriptions; one is usually situated
opposite the umbilicus, one at the extremity of the xiphoid process, and the
third about midway between the xiphoid process and the umbilicus. These
inscriptions pass transversely or obliquely across the muscle in a zigzag
course; they rarely extend completely through its substance and may pass only
halfway across it; they are intimately adherent in front to the sheath of the
muscle. Sometimes one or two additional inscriptions, generally incomplete, are
present below the umbilicus.
The interfoveolar ligament, seen from in front.
The Rectus is enclosed in a sheath formed by the aponeuroses
of the Obliqui and Transversus, which are arranged in the following manner. At
the lateral margin of the Rectus, the aponeurosis of the Obliquus internus
divides into two lamellæ, one of which passes in front of the Rectus,
blending with the aponeurosis of the Obliquus externus, the other, behind it,
blending with the aponeurosis of the Transversus, and these, joining again at
the medial border of the Rectus, are inserted into the linea alba. This
arrangement of the aponeurosis exists from the costal margin to midway between
the umbilicus and symphysis pubis, where the posterior wall of the sheath ends
in a thin curved margin, the linea semicircularis, the concavity of
which is directed downward: below this level the aponeuroses of all three
muscles pass in front of the Rectus. The Rectus, in the situation where its
sheath is deficient below, is separated from the peritoneum by the
transversalis fascia. Since the tendons of the Obliquus internus and
Transversus only reach as high as the costal margin, it follows that above this
level the sheath of the Rectus is deficient behind, the muscle resting directly
on the cartilages of the ribs, and being covered merely by the tendon of the
Obliquus externus.
The Pyramidalis is a small triangular muscle, placed
at the lower part of the abdomen, in front of the Rectus, and contained in the
sheath of that muscle. It arises by tendinous fibers from the front of
the pubis and the anterior pubic ligament; the fleshy portion of the muscle passes
upward, diminishing in size as it ascends, and ends by a pointed extremity
which is inserted into the linea alba, midway between the umbilicus and
pubis. This muscle may be wanting on one or both sides; the lower end of the
Rectus then becomes proportionately increased in size. Occasionally it is
double on one side, and the muscles of the two sides are sometimes of unequal
size. It
may extend higher than the level stated.
Diagram of sheath of Rectus.
Besides the Rectus and Pyramidalis, the sheath of the Rectus
contains the superior and inferior epigastric arteries, and the lower
intercostal nerves.
Variations.—The Rectus may insert
as high as the fourth or third rib or may fail to reach the fifth. Fibers may
spring from the lower part of the linea alba.
Nerves.—The abdominal muscles are supplied
by the lower intercostal nerves. The Obliquus internus and Transversus also
receive filaments from the anterior branch of the iliohypogastric and sometimes
from the ilioinguinal. The Cremaster is supplied by the external spermatic
branch of the genitofemoral and the Pyramidalis usually by the twelfth
thoracic.
The Linea Alba.—The linea alba is a
tendinous raphé in the middle line of the abdomen, stretching between
the xiphoid process and the symphysis pubis. It is placed between the medial
borders of the Recti, and is formed by the blending of the aponeuroses of the
Obliqui and Transversi. It is narrow below, corresponding to the linear
interval existing between the Recti; but broader above, where these muscles diverge
from one another. At its lower end the linea alba has a double attachment—its
superficial fibers passing in front of the medial heads of the Recti to the
symphysis pubis, while its deeper fibers form a triangular lamella, attached
behind the Recti to the posterior lip of the crest of the pubis, and named the adminiculum
lineæ albæ. It presents apertures for the passage of vessels
and nerves; the umbilicus, which in the fetus exists as an aperture and
transmits the umbilical vessels, is closed in the adult.
Diagram of a transverse section through the anterior abdomina wall,
below the linea semicircularis.
The Lineæ Semilunares.—The
lineæ semilunares are two curved tendinous lines placed one on either
side of the linea alba. Each corresponds with the lateral border of the Rectus,
extends from the cartilage of the ninth rib to the pubic tubercle, and is
formed by the aponeurosis of the Obliquus internus at its line of division to
enclose the Rectus, reinforced in front by that of the Obliquus externus, and
behind by that of the Transversus.
Actions.—When the pelvis and thorax are
fixed, the abdominal muscles compress the abdominal viscera by constricting the
cavity of the abdomen, in which action they are materially assisted by the
descent of the diaphragm. By these means assistance is given in expelling the
feces from the rectum, the urine from the bladder, the fetus from the uterus,
and the contents of the stomach in vomiting.
If the pelvis and vertebral column be fixed, these muscles
compress the lower part of the thorax, materially assisting expiration. If the
pelvis alone be fixed, the thorax is bent directly forward, when the muscles of
both sides act; when the muscles of only one side contract, the trunk is bent
toward that side and rotated toward the opposite side.
If the thorax be fixed, the muscles, acting together, draw
the pelvis upward, as in climbing; or, acting singly, they draw the pelvis
upward, and bend the vertebral column to one side or the other. The Recti,
acting from below, depress the thorax, and consequently flex the vertebral
column; when acting from above, they flex the pelvis upon the vertebral column.
The Pyramidales are tensors of the linea alba.
The Transversalis Fascia.—The transversalis
fascia is a thin aponeurotic membrane which lies between the inner surface of
the Transversus and the extraperitoneal fat. It forms part of the general layer
of fascia lining the abdominal parietes, and is directly continuous with the
iliac and pelvic fasciæ. In the inguinal region, the transversalis fascia
is thick and dense in structure and is joined by fibers from the aponeurosis of
the Transversus, but it becomes thin as it ascends to the diaphragm, and blends
with the fascia covering the under surface of this muscle. Behind, it is
lost in the fat which covers the posterior surfaces of the kidneys. Below,
it has the following attachments: posteriorly, to the whole length of
the iliac crest, between the attachments of the Transversus and Iliacus;
between the anterior superior iliac spine and the femoral vessels it is
connected to the posterior margin of the inguinal ligament, and is there
continuous with the iliac fascia. Medial to the femoral vessels it is thin and
attached to the pubis and pectineal line, behind the inguinal aponeurotic falx,
with which it is united; it descends in front of the femoral vessels to form
the anterior wall of the femoral sheath. Beneath the inguinal ligament it is
strengthened by a band of fibrous tissue, which is only loosely connected to
the ligament, and is specialized as the deep crural arch. The spermatic
cord in the male and the round ligament of the uterus in the female pass
through the transversalis fascia at a spot called the abdominal inguinal
ring. This opening is not visible externally, since the transversalis
fascia is prolonged on these structures as the infundibuliform fascia.
The Abdominal Inguinal Ring (annulus inguinalis abdominis; internal
or deep abdominal ring).—The abdominal inguinal
ring is situated in the transversalis fascia, midway between the anterior
superior iliac spine and the symphysis pubis, and about
The
Extraperitoneal Connective Tissue.—Between
the inner surface of the general layer of the fascia which lines the interior
of the abdominal and pelvic cavities, and the peritoneum, there is a
considerable amount of connective tissue, termed the extraperitoneal or subperitoneal
connective tissue.
The parietal portion lines the cavity in varying
quantities in different situations. It is especially abundant on the posterior
wall of the abdomen, and particularly around the kidneys, where it contains
much fat. On the anterior wall of the abdomen, except in the public region, and
on the lateral wall above the iliac crest, it is scanty, and here the
transversalis fascia is more closely connected with the peritoneum. There is a
considerable amount of extraperitoneal connective tissue in the pelvis.
The visceral portion follows the course of the
branches of the abdominal aorta between the layers of the mesenterics and other
folds of peritoneum which connect the various viscera to the abdominal wall. The two portions are
directly continuous with each other.
The abdominal inguinal ring.
The Deep Crural Arch.—Curving over the
external iliac vessels, at the spot where they become femoral, on the abdominal
side of the inguinal ligaments and loosely connected with it, is a thickened
band of fibers called the deep crural arch. It is apparently a thickening of
the transversalis fascia joined laterally to the center of the lower margin of
the inguinal ligament, and arching across the front of the femoral sheath to be
inserted by a broad attachment into the pubic tubercle and pectineal line,
behind the inguinal aponeurotic falx. In some subjects this structure is not
very prominently marked, and not infrequently it is altogether wanting.
2. The Posterior Muscles of the Abdomen
Quadratus lumborum.
The Psoas major, the Psoas minor, and the Iliacus, with the
fasciæ covering them, will be described with the muscles of the lower
extremity (see page 466).
The Fascia Covering the Quadratus Lumborum.—This
is a thin layer attached, medially, to the bases of the transverse
processes of the lumbar vertebræ; below, to the iliolumbar
ligament; above, to the apex and lower border of the last rib. The upper
margin of this fascia, which extends from the transverse process of the first
lumbar vertebra to the apex and lower border of the last rib, constitutes the
lateral lumbocostal arch (page 405). Laterally, it blends with the lumbodorsal
fascia, the anterior layer of which intervenes between the Quadratus lumborum
and the Sacrospinalis.
The Quadratus lumborum is irregularly quadrilateral
in shape, and broader below than above. It arises by aponeurotic fibers
from the iliolumbar ligament and the adjacent portion of the iliac crest for
about
Variations.—The number of
attachments to the vertebræ and the extent of its attachment to the last
rib vary.
Nerve Supply.—The twelfth thoracic
and first and second lumbar nerves supply this muscle.
Actions.—The Quadratus lumborum draws
down the last rib, and acts as a muscle of inspiration by helping to fix the
origin of the diaphragm. If the thorax and vertebral column are fixed, it may
act upon the pelvis, raising it toward its own side when only one muscle is put
in action; and when both muscles act together, either from below or above, they
flex the trunk.
The
Extraperitoneal Connective Tissue.—Between the inner surface of the general layer of the fascia which
lines the interior of the abdominal and pelvic cavities, and the peritoneum,
there is a considerable amount of connective tissue, termed the extraperitoneal
or subperitoneal connective tissue.
The parietal portion lines the
cavity in varying quantities in different situations. It is especially abundant
on the posterior wall of the abdomen, and particularly around the kidneys,
where it contains much fat. On the anterior wall of the abdomen, except in the
public region, and on the lateral wall above the iliac crest, it is scanty, and
here the transversalis fascia is more closely connected with the peritoneum.
There is a considerable amount of extraperitoneal connective tissue in the
pelvis.
The visceral portion follows the
course of the branches of the abdominal aorta between the layers of the
mesenterics and other folds of peritoneum which connect the various viscera to
the abdominal wall. The two portions are directly continuous with each other.
The abdominal inguinal ring.
The Deep Crural Arch.—Curving
over the external iliac vessels, at the spot where they become femoral, on the
abdominal side of the inguinal ligaments and loosely connected with it, is a
thickened band of fibers called the deep crural arch. It is apparently a
thickening of the transversalis fascia joined laterally to the center of the
lower margin of the inguinal ligament, and arching across the front of the
femoral sheath to be inserted by a broad attachment into the pubic tubercle and
pectineal line, behind the inguinal aponeurotic falx. In some subjects this
structure is not very prominently marked, and not infrequently it is altogether
wanting.
They differ some regions in abdomen:
In Epigastrium (upper floor) –
Right Hypochondriac
Epigastric, Left Hypochondriac regions
In
Mesogastrium (middle floor) –
Right Lateral, Umbilical and Left Lateral regions
In Hypogastrium
(lower floor) –
Right Inguinal, Pubic and Left Inguinal regions
Back surface of front abdominal wall is covered by parietal sheet of
peritoneum and carries unpaired median
umbilical fold (plicae) and paired – medial and lateral umbilical
folds (plicae). Medial umbilical fossa projected into
superficial inguinal ring, which positioned between medial and lateral
umbilical folds. Straight inguinal
herniae can pass through this fossa. Lateral
umbilical fossa placed laterally from lateral umbilical fold. It answers
the deep inguinal ring and during pathologic cases can contain oblique inguinal
herniae. There is supravesical fossa
between median and medial umbilical folds.
Deltoid
· Origin:
1. lateral, anterior 1/3 of distal clavicle
2. lateral boarder of the acromion
3. scapular spine
· Insertion:
deltoid tuberosity of humerus
· Action:
1. abducts arm
2. flexion and
medial rotation (anterior portion)
3. extension and lateral rotation (posterior portion)
· Blood:
1. posterior humeral circumflex artery
2. deltoid branch of thoracoacromial artery
· Nerve:
axillary nerve, C5,6
Supraspinatus
· Origin:
1. supraspinous fossa
2. muscle fascia
· Insertion:
uppermost of three facets of the greater tubercle of humerus
· Action:
1. abduction of arm (first 15-20°)
2. stabilizes
glenohumeral joint
· Blood:
suprascapular artery (poorly supplied)
· Nerve:
suprascapular nerve, C5,6
Infraspinatus
· Origin:
1. infraspinous fossa
2. muscle fascia
· Insertion:
middle facet of greater tubercle of humerus
· Action:
1. external rotation of the humerus
2. stabilizes
the glenohumeral joint
· Blood:
1. suprascapular artery
2. scapular circumflex artery
· Nerve:
suprascapular nerve, C5,6
Teres minor
· Origin:
middle half of the scapula’s lateral margin
· Insertion:
lowest of three facets of the greater tubercle of humerus
· Action:
1. lateral rotation of the humerus
2. stabilizes
the glenohumeral joint
· Blood:
scapular circumflex artery
· Nerve:
axillary nerve, C5,6
Teres major
· Origin:
inferior, lateral margin of the scapula
· Insertion:
crest of lesser tubercle (just medial to the insertion of latissimus dorsi)
· Action:
1. assists in adduction of arm
2. assists in medial rotation of arm
3. assists in extension from an flexed position
· Blood:
thoracodorsal artery
· Nerve:
lower subscapular nerve, C5,6
Subscapularis
· Origin:
subscapular fossa
· Insertion:
lesser tubercle of humerus
· Action:
1. medial rotation of the humerus
2. stabilizes
the glenohumeral joint
· Blood:
Branches of subscapular artery
· Nerve:
upper & lower subscapular nerves, C5,6
Brachium (arm) Musculature
ANTERIOR GROUP
Coracobrachialis
• Origin: coracoid process of the scapula • Insertion: medial shaft of
the humerus at about its middle • Action:
1.flexes the humerus
2.assists to adduct the humerus
• Blood: muscular branches of the brachial artery • Nerve:
musculocutaneous nerve, C5,6,(C7)
Biceps brachii
• Origin:
1.long head-
supraglenoid tubercle and glenohumeral labrum 2.short head- tip of the coracoid
process of the scapula
• Insertion:
1.radial tuberosity
2.bicipital aponeurosis
• Action:
1.flexes the forearm
at the elbow (when supinated) 2.supinates forearm from neutral 3.stabilizes
anterior aspect of shoulder 4.flexes shoulder (weak if at all)
• Blood: muscular branches of brachial artery • Nerve: musculocutaneous
nerve, C5,6
Brachialis
• Origin:
1.lower 1/2 of
anterior humerus 2.both intermuscular septa
• Insertion:
1.ulnar tuberosity
2.coronoid process of ulna slightly
• Action: elbow flexion (major mover) • Blood:
1.muscular branches of
brachial artery 2.radial recurrent artery
• Nerve: musculocutaneous nerve, C5,6
POSTERIOR GROUP
Triceps brachii
• Origin:
1.long head - infraglenoid tubercle of the scapula 2.lateral head - upper
half of the posterior surface of the shaft of the humerus, and the upper part
of the lateral intermuscular septum 3.medial head - posterior shaft of humerus,
distal to radial groove and both the medial and lateral intermuscular septum
(deep to the long & lateral heads)
• Insertion:
1.posterior surface of
the olecranon process of the ulna 2.deep fascia of the antebrachium
• Action:
1.long - adducts
the arm, extends at the shoulder, and a little elbow flexion 2.lateral -
extends the forearm at the elbow 3.medial - extends the forearm at the elbow
• Blood:
1.muscular branches of
the brachial artery 2.superior ulnar collateral artery 3.profunda brachii
artery
• Nerve: radial nerve, C6,7
Cross-section through
the middle of upper arm. (Eycleshymer and Schoemaker.)
Anconeus
• Origin: posterior surface of the lateral epicondyle of the humerus •
Insertion: lateral aspect of olecranon extending to the lateral part of ulnar
body • Action:
1.extends the forearm
at the elbow 2.supports the elbow when in full extension
• Blood: middle collateral artery from the profunda brachii artery •
Nerve: radial nerve, C7,8
Theme 2. THE MUSCLES OF THE FOREARM AND
HAND.
The antibrachial or forearm muscles may be divided into a volar
and a dorsal group.
The Volar Antibrachial Muscles—These muscles are divided for convenience of description
into two groups, superficial and deep.
The Superficial Group
Pronator teres.
Palmaris longus.
Flexor carpi radialis.
Flexor carpi ulnaris.
Flexor digitorum sublimis.
The muscles of this group take origin from the medial
epicondyle of the humerus by a common tendon; they receive additional fibers
from the deep fascia of the forearm near the elbow, and from the septa which
pass from this fascia between the individual muscles.
The Pronator teres has two heads of origin—humeral
and ulnar. The humeral head, the larger and more superficial, arises
immediately above the medial epicondyle, and from the tendon common to the
origin of the other muscles; also from the intermuscular septum between it and
the Flexor carpi radialis and from the antibrachial fascia. The ulnar head
is a thin fasciculus, which arises from the medial side of the coronoid
process of the ulna, and joins the preceding at an acute angle. The median nerve
enters the forearm between the two heads of the muscle, and is separated from
the ulnar artery by the ulnar head. The muscle passes obliquely across the
forearm, and ends in a flat tendon, which is inserted into a rough impression
at the middle of the lateral surface of the body of the radius. The lateral
border of the muscle forms the medial boundary of a triangular hollow situated
in front of the elbow-joint and containing the brachial artery, median nerve,
and tendon of the Biceps brachii.
Variations.—Absence of ulnar head; additional slips from
the medial intermuscular septum, from the Biceps and from the Brachialis
anticus occasionally occur.
The Flexor carpi radialis lies on the medial side of
the preceding muscle. It arises from the medial epicondyle by the common
tendon; from the fascia of the forearm; and from the intermuscular septa
between it and the Pronator teres laterally, the Palmaris longus medially, and
the Flexor digitorum sublimis beneath. Slender and aponeurotic in structure at
its commencement, it increases in size, and ends in a tendon which forms rather
more than the lower half of its length. This tendon passes through a canal in
the lateral part of the transverse carpal ligament and runs through a groove on
the greater multangular bone; the groove is converted into a canal by fibrous
tissue, and lined by a mucous sheath. The tendon is inserted into the base of
the second metacarpal bone, and sends a slip to the base of the third
metacarpal bone. The radial artery, in the lower part of the forearm, lies
between the tendon of this muscle and the Brachioradialis.
Variations.—Slips from the tendon
of the Biceps, the lacertus fibrosus, the coronoid, and the radius have been
found. Its insertion often varies and may be mostly into the annular ligament,
the trapezium, or the fourth metacarpal as well as the second or third. The
muscle may be absent.
The Palmaris longus is a slender, fusiform muscle,
lying on the medial side of the preceding. It arises from the medial
epicondyle of the humerus by the common tendon, from the intermuscular septa
between it and the adjacent muscles, and from the antibrachial fascia. It ends
in a slender, flattened tendon, which passes over the upper part of the
transverse carpal ligament, and is inserted into the central part of the
transverse carpal ligament and lower part of the palmar aponeurosis, frequently
sending a tendinous slip to the short muscles of the thumb.
Variations.—One
of the most variable muscles in the body. This muscle is often absent about (10
per cent.), and is subject to many variations; it may be tendinous above and
muscular below; or it may be muscular in the center with a tendon above and
below; or it may present two muscular bundles with a central tendon; or finally
it may consist solely of a tendinous band. The muscle may be double. Slips of
origin from the coronoid process or from the radius have been seen.Partial or
complete insertion into the fascia of the forearm, into the tendon of the
Flexor carpi ulnaris and pisiform bone, into the navicular, and into the
muscles of the little finger have been observed.
Front of the left forearm. Superficial muscles.
Front of the left forearm. Deep muscles.
The Flexor carpi ulnaris lies along the ulnar side of
the forearm. It arises by two heads, humeral and ulnar, connected by a
tendinous arch, beneath which the ulnar nerve and posterior ulnar recurrent
artery pass. The humeral head arises from the medial epicondyle
of the humerus by the common tendon; the ulnar head arises from
the medial margin of the olecranon and from the upper two-thirds of the dorsal
border of the ulna by an aponeurosis, common to it and the Extensor carpi
ulnaris and Flexor digitorum profundus; and from the intermuscular septum
between it and the Flexor digitorum sublimis. The fibers end in a tendon, which
occupies the anterior part of the lower half of the muscle and is inserted
into the pisiform bone, and is prolonged from this to the hamate and fifth
metacarpal bones by the pisohamate and pisometacarpal ligaments; it is also
attached by a few fibers to the transverse carpal ligament. The ulnar vessels
and nerve lie on the lateral side of the tendon of this muscle, in the lower
two-thirds of the forearm.
Variations.—Slips of origin from
the coronoid. The Epitrochleo-anconæus, a small muscle often
present runs from the back of the inner condyle to the olecranon, over the
ulnar nerve.
The Flexor digitorum is placed beneath the previous
muscle; it is the largest of the muscles of the superficial group, and arises
by three heads—humeral, ulnar, and radial. The humeral head arises
from the medial epicondyle of the humerus by the common tendon, from the ulnar
collateral ligament of the elbow-joint, and from the intermuscular septa
between it and the preceding muscles. The ulnar head arises from
the medial side of the coronoid process, above the ulnar origin of the Pronator
teres. The radial head arises from the oblique line of the
radius, extending from the radial tuberosity to the insertion of the Pronator
teres. The muscle speedily separates into two planes of muscular fibers, superficial
and deep: the superficial plane divides into two parts which end in tendons for
the middle and ring fingers; the deep plane gives off a muscular slip to join
the portion of the superficial plane which is associated with the tendon of the
ring finger, and then divides into two parts, which end in tendons for the
index and little fingers. As the four tendons thus formed pass beneath the
transverse carpal ligament into the palm of the hand, they are arranged in
pairs, the superficial pair going to the middle and ring fingers, the deep pair
to the index and little fingers. The tendons diverge from one another in the
palm and form dorsal relations to the superficial volar arch and digital
branches of the median and ulnar nerves. Opposite the bases of the first
phalanges each tendon divides into two slips to allow of the passage of the
corresponding tendon of the Flexor digitorum profundus; the two slips then
reunite and form a grooved channel for the reception of the accompanying tendon
of the Flexor digitorum profundus. Finally the tendon divides and is inserted
into the sides of the second phalanx about its middle.
Variations.—Absence of radial head, of little finger
portion; accessory slips from ulnar tuberosity to the index and middle finger
portions; from the inner head to the Flexor profundus; from the ulnar or
annular ligament to the little finger.
The Deep Group
Flexor digitorum profundus.
Flexor pollicis longus.
Pronator quadratus.
The Flexor digitorum profundus is situated on the
ulnar side of the forearm, immediately beneath the superficial Flexors. It arises
from the upper three-fourths of the volar and medial surfaces of the body of
the ulna, embracing the insertion of the Brachialis above, and extending below
to within a short distance of the Pronator quadratus. It also arises from a
depression on the medial side of the coronoid process; by an aponeurosis from
the upper three-fourths of the dorsal border of the ulna, in common with the
Flexor and Extensor carpi ulnaris; and from the ulnar half of the interosseous
membrane. The muscle ends in four tendons which run under the transverse carpal
ligament dorsal to the tendons of the Flexor digitorum sublimis. Opposite the
first phalanges the tendons pass through the openings in the tendons of the
Flexor digitorum sublimis, and are finally inserted into the bases of
the last phalanges. The portion of the muscle for the index finger is usually
distinct throughout, but the tendons for the middle, ring, and little fingers
are connected together by areolar tissue and tendinous slips, as far as the
palm of the hand.
Variations.—The
index finger portion may arise partly from the upper part of the radius. Slips
from the inner head of the Flexor sublimis, medial epicondyle, or the coronoid
are found. Connection with the Flexor pollicis longus.
Four small muscles, the Lumbricales, are connected with the
tendons of the Flexor profundus in the palm. They will be described with the
muscles of the hand.
The Flexor pollicis longus is situated on the radial
side of the forearm, lying in the same plane as the preceding. It arises
from the grooved volar surface of the body of the radius, extending from
immediately below the tuberosity and oblique line to within a short distance of
the Pronator quadratus. It arises also from the adjacent part of the
interosseous membrane, and generally by a fleshy slip from the medial border of
the coronoid process, or from the medial epicondyle of the humerus. The fibers
end in a flattened tendon, which passes beneath the transverse carpal ligament,
is then lodged between the lateral head of the Flexor pollicis brevis and the
oblique part of the Adductor pollicis, and, entering an osseoaponeurotic canal
similar to those for the Flexor tendons of the fingers, is inserted into
the base of the distal phalanx of the thumb. The volar interosseous nerve and
vessels pass downward on the front of the interosseous membrane between the
Flexor pollicis longus and Flexor digitorum profundus.
Variations.—Slips may connect with
Flexor sublimis, or Profundus, or Pronator teres. An additional tendon to the
index finger is sometimes found.
The Pronator quadratus is a small, flat,
quadrilateral muscle, extending across the front of the lower parts of the
radius and ulna. It arises from the pronator ridge on the lower part of
the volar surface of the body of the ulna; from the medial part of the volar
surface of the lower fourth of the ulna; and from a strong aponeurosis which
covers the medial third of the muscle. The fibers pass lateralward and slightly
downward, to be inserted into the lower fourth of the lateral border and the
volar surface of the body of the radius. The deeper fibers of the muscle are
inserted into the triangular area above the ulnar notch of the radius—an
attachment comparable with the origin of the Supinator from the triangular area
below the radial notch of the ulna.
Tendons of forefinger and vincula
tendina.
Variations.—Rarely
absent; split into two or three layers; increased attachment upward or
downward.
Nerves.—All the
muscles of the superficial layer are supplied by the median nerve, excepting
the Flexor carpi ulnaris, which is supplied by the ulnar. The
Pronator teres, the Flexor carpi radialis, and the Palmaris longus derive their
supply primarily from the sixth cervical nerve; the Flexor digitorum sublimis
from the seventh and eighth cervical and first thoracic nerves, and the Flexor
carpi ulnaris from the eighth cervical and first thoracic. Of the deep
layer, the Flexor digitorum profundus is supplied by the eighth cervical and
first thoracic through the ulnar, and the volar interosseous branch of the
median. The Flexor pollicis longus and Pronator quadratus are supplied by the
eighth cervical and first thoracic through the volar interosseous branch of the
median.
Actions.—These
muscles act upon the forearm, the wrist, and hand. The Pronator teres rotates
the radius upon the ulna, rendering the hand prone; when the radius is fixed,
it assists in flexing the forearm. The Flexor carpi radialis is a flexor and abductor
of the wrist; it also assists in pronating the hand, and in bending the elbow.
The Flexor carpi ulnaris is a flexor and adductor of the wrist; it also assists
in bending the elbow. The Palmaris longus is a flexor of the wrist-joint; it
also assists in flexing the elbow. The Flexor digitorum sublimis flexes first
the middle and then the proximal phalanges; it also assists in flexing the
wrist and elbow. The Flexor digitorum profundus is one of the flexors of the
phalanges. After the Flexor sublimis has bent the second phalanx, the Flexor
profundus flexes the terminal one; but it cannot do so until after the
contraction of the superficial muscle. It also assists in flexing the wrist.
The Flexor pollicis longus is a flexor of the phalanges of the thumb; when the
thumb is fixed, it assists in flexing the wrist. The Pronator quadratus rotates
the radius upon the ulna, rendering the hand prone.
Cross-section through the middle of the
forearm.
2. The Dorsal Antibrachial Muscles—These muscles are divided for convenience of description
into two groups, superficial and deep.
The Superficial Group
Brachioradialis.
Extensor digitorum communis.
Extensor carpi radialis longus.
Extensor digiti quinti proprius.
Extensor carpi radialis brevis.
Extensor carpi ulnaris.
Anconæus.
The Brachioradialis (Supinator longus) is the
most superficial muscle on the radial side of the forearm. It arises
from the upper two-thirds of the lateral supracondylar ridge of the humerus,
and from the lateral intermuscular septum, being limited above by the groove
for the radial nerve. Interposed between it and the Brachialis are the radial
nerve and the anastomosis between the anterior branch of the profunda artery
and the radial recurrent. The fibers end above the middle of the forearm in a
flat tendon, which is inserted into the lateral side of the base of the
styloid process of the radius. The tendon is crossed near its insertion by the
tendons of the Abductor pollicis longus and Extensor pollicis brevis; on its
ulnar side is the radial artery.
Variations.—Fusion with the
Brachialis; tendon of insertion may be divided into two or three slips;
insertion partial or complete into the middle of the radius, fasciculi to the
tendon of the Biceps, the tuberosity or oblique line of the radius; slips to
the Extensor carpi radialis longus or Abductor pollicis longus; absence; rarely
doubled.
The Extensor carpi radialis longus (Extensor carpi
radialis longior) is placed partly beneath the Brachioradialis. It arises
from the lower third of the lateral supracondylar ridge of the humerus, from
the lateral intermuscular septum, and by a few fibers from the common tendon of
origin of the Extensor muscles of the forearm. The fibers end at the upper
third of the forearm in a flat tendon, which runs along the lateral border of
the radius, beneath the Abductor pollicis longus and Extensor pollicis brevis;
it then passes beneath the dorsal carpal ligament, where it lies in a groove on
the back of the radius common to it and the Extensor carpi radialis brevis,
immediately behind the styloid process. It is inserted into the dorsal
surface of the base of the second metacarpal bone, on its radial side.
The Extensor carpi radialis brevis (Extensor carpi
radialis brevior) is shorter and thicker than the preceding muscle, beneath
which it is placed. It arises from the lateral epicondyle of the
humerus, by a tendon common to it and the three following muscles; from the
radial collateral ligament of the elbow-joint; from a strong aponeurosis which
covers its surface; and from the intermuscular septa between it and the
adjacent muscles. The fibers end about the middle of the forearm in a flat
tendon, which is closely connected with that of the preceding muscle, and
accompanies it to the wrist; it passes beneath the Abductor pollicis longus and
Extensor pollicis brevis, then beneath the dorsal carpal ligament, and is inserted
into the dorsal surface of the base of the third metacarpal bone on its radial
side. Under the dorsal carpal ligament the tendon lies on the back of the
radius in a shallow groove, to the ulnar side of that which lodges the tendon
of the Extensor carpi radialis, longus, and separated from it by a faint ridge.
The tendons of the two preceding muscles pass through the
same compartment of the dorsal carpal ligament in a single mucous sheath.
Variations.—Either
muscle may split into two or three tendons of insertion to the second and third
or even the fourth metacarpal. The two muscles may unite into a single belly
with two tendons. Cross slips between the two muscles may occur. The Extensor
carpi radialis intermedius rarely arises as a distinct muscle from the
humerus, but is not uncommon as an accessory slip from one or both muscles to
the second or third or both metacarpals. The Extensor carpi radialis
accessorius is occasionally found arising from the humerus with or below
the Extensor carpi radialis longus and inserted into the first metacarpal, the
Abductor pollicis brevis, the First dorsal interosseous, or elsewhere.
The Extensor digitorum communis arises from
the lateral epicondyle of the humerus, by the common tendon; from the
intermuscular septa between it and the adjacent muscles, and from the
antibrachial fascia. It divides below into four tendons, which pass, together
with that of the Extensor indicis proprius, through a separate compartment of
the dorsal carpal ligament, within a mucous sheath. The tendons then diverge on
the back of the hand, and are inserted into the second and third
phalanges of the fingers in the following manner. Opposite the
metacarpophalangeal articulation each tendon is bound by fasciculi to the
collateral ligaments and serves as the dorsal ligament of this joint; after
having crossed the joint, it spreads out into a broad aponeurosis, which covers
the dorsal surface of the first phalanx and is reinforced, in this situation,
by the tendons of the Interossei and Lumbricalis. Opposite the first
interphalangeal joint this aponeurosis divides into three slips; an
intermediate and two collateral: the former is
inserted into the base of the second phalanx; and the two collateral, which are
continued onward along the sides of the second phalanx, unite by their
contiguous margins, and are inserted into the dorsal surface of the last
phalanx. As the tendons cross the interphalangeal joints, they furnish them
with dorsal ligaments. The tendon to the index finger is accompanied by the
Extensor indicis proprius, which lies on its ulnar side. On the back of the
hand, the tendons to the middle, ring, and little fingers are connected by two
obliquely placed bands, one from the third tendon passing downward and
lateralward to the second tendon, and the other passing from the same tendon
downward and medialward to the fourth. Occasionally the first tendon is connected
to the second by a thin transverse band.
Posterior surface of the forearm. Superficial muscles.
Posterior surface of the forearm. Deep muscles.
Variations.—An
increase or decrease in the number of tendons is common; an additional slip to
the thumb is sometimes present.
The Extensor digiti quinti proprius (Extensor
minimi digiti) is a slender muscle placed on the medial side of the
Extensor digitorum communis, with which it is generally connected. It arises
from the common Extensor tendon by a thin tendinous slip, from the
intermuscular septa between it and the adjacent muscles. Its tendon runs
through a compartment of the dorsal carpal ligament behind the distal
radio-ulnar joint, then divides into two as it crosses the hand, and finally
joins the expansion of the Extensor digitorum communis tendon on the dorsum of
the first phalanx of the little finger.
Variations.—An
additional fibrous slip from the lateral epicondyle; the tendon of insertion
may not divide or may send a slip to the ring finger. Absence
of muscle rare; fusion of the belly with the Extensor digitorum communis not
uncommon.
The Extensor carpi ulnaris lies on the ulnar side of
the forearm. It arises from the lateral epicondyle of the humerus, by
the common tendon; by an aponeurosis from the dorsal border of the ulna in
common with the Flexor carpi ulnaris and the Flexor digitorum profundus; and
from the deep fascia of the forearm. It ends in a tendon, which runs in a
groove between the head and the styloid process of the ulna, passing through a
separate compartment of the dorsal carpal ligament, and is inserted into
the prominent tubercle on the ulnar side of the base of the fifth metacarpal
bone.
Variations.—Doubling;
reduction to tendinous band; insertion partially into fourth metacarpal. In many cases (52 per cent.) a slip is continued from the insertion of
the tendon anteriorly over the Opponens digiti quinti, to the fascia covering
that muscle, the metacarpal bone, the capsule of the metacarpophalangeal
articulation, or the first phalanx of the little finger. This slip may be
replaced by a muscular fasciculus arising from or near the pisiform.
The Anconæus is a small triangular muscle which
is placed on the back of the elbow-joint, and appears to be a continuation of
the Triceps brachii. It arises by a separate tendon from the back part
of the lateral epicondyle of the humerus; its fibers diverge and are inserted
into the side of the olecranon, and upper fourth of the dorsal surface of the
body of the ulna.
The Deep Group
Supinator.
Extensor pollicis brevis.
Abductor pollicis longus.
Extensor pollicis longus.
Extensor indicis proprius.
The Supinator (Supinator brevis) is a broad
muscle, curved around the upper third of the radius. It consists of two planes
of fibers, between which the deep branch of the radial nerve lies. The two
planes arise in common—the superficial one by tendinous and the deeper
by muscular fibers—from the lateral epicondyle of the humerus; from the radial
collateral ligament of the elbow-joint, and the annular ligament; from the
ridge on the ulna, which runs obliquely downward from the dorsal end of the
radial notch; from the triangular depression below the notch; and from a
tendinous expansion which covers the surface of the muscle. The superficial
fibers surround the upper part of the radius, and are inserted into the lateral
edge of the radial tuberosity and the oblique line of the radius, as low down
as the insertion of the Pronator teres. The upper fibers of the deeper plane
form a sling-like fasciculus, which encircles the neck of the radius above the
tuberosity and is attached to the back part of its medial surface; the greater
part of this portion of the muscle is inserted into the dorsal and lateral
surfaces of the body of the radius, midway between the oblique line and the
head of the bone.
The Abductor pollicis longus (Extensor oss.
metacarpi pollicis) lies immediately below the Supinator and is sometimes
united with it. It arises from the lateral part of the dorsal surface of
the body of the ulna below the insertion of the Anconæus, from the
interosseous membrane, and from the middle third of the dorsal surface of the
body of the radius. Passing obliquely downward and lateralward, it ends in a
tendon, which runs through a groove on the lateral side of the lower end of the
radius, accompanied by the tendon of the Extensor pollicis brevis, and is inserted
into the radial side of the base of the first metacarpal bone. It occasionally
gives off two slips near its insertion: one to the greater multangular bone and
the other to blend with the origin of the Abductor pollicis brevis.
Variations.—More
or less doubling of muscle and tendon with insertion of the extra tendon into
the first metacarpal, the greater multangular, or into the Abductor pollicis
brevis or Opponens pollicis.
The Supinator.
The Extensor pollicis brevis (Extensor primi
internodii pollicis) lies on the medial side of, and is closely connected
with, the Abductor pollicis longus. It arises from the dorsal surface of
the body of the radius below that muscle, and from the interosseous membrane.
Its direction is similar to that of the Abductor pollicis longus, its tendon
passing the same groove on the lateral side of the lower end of the radius, to
be inserted into the base of the first phalanx of the thumb.
Variations.—Absence;
fusion of tendon with that of the Extensor pollicis longus.
The Extensor pollicis longus (Extensor secundi
internodii pollicis) is much larger than the preceding muscle, the origin
of which it partly covers. It arises from the lateral part of the middle
third of the dorsal surface of the body of the ulna below the origin of the
Abductor pollicis longus, and from the interosseous membrane. It ends in a
tendon, which passes through a separate compartment in the dorsal carpal
ligament, lying in a narrow, oblique groove on the back of the lower end of the
radius. It then crosses obliquely the tendons of the Extensores carpi radialis
longus and brevis, and is separated from the Extensor brevis pollicis by a
triangular interval, in which the radial artery is found; and is finally inserted
into the base of the last phalanx of the thumb. The radial artery is crossed by
the tendons of the Abductor pollicis longus and of the Extensores pollicis
longus and brevis.
The Extensor indicis proprius (Extensor indicis)
is a narrow, elongated muscle, placed medial to, and parallel with, the
preceding. It arises, from the dorsal surface of the body of the ulna
below the origin of the Extensor pollicis longus, and from the interosseous
membrane. Its tendon passes under the dorsal carpal ligament in the same
compartment as that which transmits the tendons of the Extensor digitorum
communis, and opposite the head of the second metacarpal bone, joins the ulnar
side of the tendon of the Extensor digitorum communis which belongs to the
index finger.
Variations.—Doubling; the ulnar
part may pass beneath the dorsal carpal ligament with the Extensor digitorum
communis; a slip from the tendon may pass to the index finger.
Nerves.—The Brachioradialis is supplied by the fifth and
sixth, the Extensores carpi radialis longus and brevis by the sixth and
seventh, and the Anconæus by the seventh and eighth cervical nerves,
through the radial nerve; the remaining muscles are innervated through the deep
radial nerve, the Supinator being supplied by the sixth, and all the other
muscles by the seventh cervical.
Actions.—The muscles of the
lateral and dorsal aspects of the forearm, which comprise all the Extensor
muscles and the Supinator, act upon the forearm, wrist, and hand; they are the
direct antagonists of the Pronator and Flexor muscles. The Anconæus
assists the Triceps in extending the forearm. The Brachioradialis is a flexor
of the elbow-joint, but only acts as such when the movement of flexion has been
initiated by the Biceps brachii and Brachialis. The action of the Supinator is
suggested by its name; it assists the Biceps in bringing the hand into the
supine position. The Extensor carpi radialis longus extends the wrist and
abducts the hand. It may also assist in bending the elbow-joint; at all events
it serves to fix or steady this articulation. The Extensor carpi radialis
brevis extends the wrist, and may also act slightly as an abductor of the hand.
The Extensor carpi ulnaris extends the wrist, but when acting alone inclines
the hand toward the ulnar side; by its continued action it extends the
elbow-joint. The Extensor digitorum communis extends the phalanges, then the
wrist, and finally the elbow. It acts principally on the proximal phalanges,
the middle and terminal phalanges being extended mainly by the Interossei and
Lumbricales. It tends to separate the fingers as it extends them. The Extensor
digiti quinti proprius extends the little finger, and by its continued action
assists in extending the wrist. It is owing to this muscle that the little
finger can be extended or pointed while the others are flexed. The chief action
of the Abductor pollicis longus is to carry the thumb laterally from the palm
of the hand. By its continued action it helps to extend and abduct the wrist.
The Extensor pollicis brevis extends the proximal phalanx, and the Extensor
pollicis longus the terminal phalanx of the thumb; by their continued action
they help to extend and abduct the wrist. The Extensor indicis proprius extends
the index finger, and by its continued action assists in extending the wrist.
2. The Medial Volar Muscles
Palmaris brevis.
Flexor digiti quinti brevis.
Abductor digiti quinti.
Opponens digiti quinti.
The Palmaris brevis is a thin, quadrilateral muscle,
placed beneath the integument of the ulnar side of the hand. It arises
by tendinous fasciculi from the transverse carpal ligament and palmar
aponeurosis; the fleshy fibers are inserted into the skin on the ulnar border
of the palm of the hand.
FIG. 427– The muscles of the left hand. Palmar surface. (See enlarged image)
The Abductor digiti quinti (Abductor minimi digiti)
is situated on the ulnar border of the palm of the hand. It arises from
the pisiform bone and from the tendon of the Flexor carpi ulnaris, and ends in
a flat tendon, which divides into two slips; one is inserted into the
ulnar side of the base of the first phalanx of the little finger; the other
into the ulnar border of the aponeurosis of the Extensor digiti quinti
proprius.
The Flexor digiti quinti brevis (Flexor brevis
minimi digiti) lies on the same plane as the preceding muscle, on its
radial side. It arises from the convex surface of the hamulus of the
hamate bone, and the volar surface of the transverse carpal ligament, and is inserted
into the ulnar side of the base of the first phalanx of the little finger. It
is separated from the Abductor, at its origin, by the deep branches of the
ulnar artery and nerve. This muscle is sometimes wanting; the Abductor is then,
usually, of large size.
The Opponens digiti quinti (Opponens minimi digiti)
(Fig. 426) is of a triangular form, and placed immediately beneath the preceding
muscles. It arises from the convexity of the hamulus of the hamate bone,
and contiguous portion of the transverse carpal ligament; it is inserted into
the whole length of the metacarpal bone of the little finger, along its ulnar
margin.
Variations.—The
Palmaris brevis varies greatly in size. The Abductor digiti quinti may be
divided into two or three slips or united with the Flexor digiti quinti brevis.
Accessory head from the tendon of the Flexor carpi ulnaris,
the transverse carpal ligament, the fascia of the forearm or the tendon of the
Palmaris longus. A portion of the muscle may insert into the metacarpal,
or separate slips the Pisimetacarpus, Pisiuncinatus or the Pisiannularis
muscle may exist.
Nerves.—All the
muscles of this group are supplied by the eighth cervical nerve through the
ulnar nerve.
Actions.—The Abductor and Flexor digiti
quinti brevis abduct the little finger from the ring finger and assist in
flexing the proximal phalanx. The Opponens digiti quinti draws forward the
fifth metacarpal bone, so as to deepen the hollow of the palm. The Palmaris
brevis corrugates the skin on the ulnar side of the palm.
3. The Intermediate Muscles
Lumbricales.
Interossei.
The Lumbricales (Fig. 427) are four small fleshy fasciculi, associated with the tendons of the
Flexor digitorum profundus. The first and second arise from the radial
sides and volar surfaces of the tendons of the index and middle fingers
respectively; the third, from the contiguous sides of the tendons of the middle
and ring fingers; and the fourth, from the contiguous sides of the tendons of
the ring and little fingers. Each passes to the radial side of the
corresponding finger, and opposite the metacarpophalangeal articulation is inserted
into the tendinous expansion of the Extensor digitorum communis covering the
dorsal aspect of the finger.
Variations.—The
Lumbricales vary in number from two to five or six and there is considerable
variation in insertions.
The Interossei (Figs. 428,
429) are so named from occupying the intervals between the metacarpal
bones, and are divided into two sets, a dorsal and a volar.
The Interossei dorsales (Dorsal interossei)
are four in number, and occupy the intervals between the metacarpal
bones. They are bipenniform muscles, each arising by two heads from the
adjacent sides of the metacarpal bones, but more extensively from the
metacarpal bone of the finger into which the muscle is inserted. They are
inserted into the bases of the first phalanges and into the aponeuroses of the
tendons of the Extensor digitorum communis. Between the double origin of each
of these muscles is a narrow triangular interval; through the first of these
the radial artery passes; through each of the other three a perforating branch
from the deep volar arch is transmitted.
The first or Abductor indicis is larger than
the others. It is flat, triangular in form, and arises by two heads,
separated by a fibrous arch for the passage of the radial artery from the
dorsum to the palm of the hand. The lateral head arises from the
proximal half of the ulnar border of the first metacarpal bone; the medial
head, from almost the entire length of the radial border of the second
metacarpal bone; the tendon is inserted into the radial side of the index
finger. The second and third are inserted into
the middle finger, the former into its radial, the latter into its ulnar side.
The fourth is inserted into the ulnar side of the ring finger.
The Interossei volares (Palmar
interossei), three in number, are smaller than the Interossei dorsales, and
placed upon the volar surfaces of the metacarpal bones, rather than between
them. Each arises from the entire length of the metacarpal bone
of one finger, and is inserted into the side of the base of the first phalanx
and aponeurotic expansion of the Extensor communis tendon to the same finger.
The first arises from the ulnar side of the
second metacarpal bone, and is inserted into the same side of the first
phalanx of the index finger. The second arises from the radial
side of the fourth metacarpal bone, and is inserted into the same side
of the ring finger. The third arises from the radial side of the
fifth metacarpal bone, and is inserted into the same side of the little
finger. From this account it may be seen that each finger is provided with two
Interossei, with the exception of the little finger, in which the Abductor
takes the place of one of the pair.
As already mentioned (p. 461), the medial head of the Flexor
pollicis brevis is sometimes described as the Interosseus volaris primus.
The Interossei dorsales of left hand.
The Interossei volares of left hand.
Nerves.—The two
lateral Lumbricales are supplied by the sixth and seventh cervical nerves, through
the third and fourth digital branches of the median nerve; the two medial
Lumbricales and all the Interossei are supplied by the eighth cervical nerve,
through the deep palmar branch of the ulnar nerve. The third Lumbricalis
frequently receives a twig from the median.
Actions.—The Interossei volares adduct the
fingers to an imaginary line drawn longitudinally through the center of the
middle finger; and the Interossei dorsales abduct the fingers from that line.
In addition to this the Interossei, in conjunction with the Lumbricales, flex
the first phalanges at the metacarpophalangeal joints, and extend the second
and third phalanges in consequence of their insertions into the expansions of
the Extensor tendons. The Extensor digitorum communis is believed to act almost
entirely on the first phalanges.
References:
TEXTBOOKS
REQUIRED
1.Author
David Shier, Jackie Butler, Ricki
Lewis Number Of Pages 640 pages Format Hardcover Publication Date 2011-01-11
Language English PublisherMcGraw-Hill
Higher Education
2.Synopses
of Human Anatomy and Physiology.
Author: Elaine N. Marieb, Katja N. Hoehn
Anatomy, Physiology Edition
Description: Revised Special Attributes: International
Edition, Brand New, College Textbook, Publication Year: 2011
3.Human
Anatomy & Physiology (9th Edition) [Hardcover]
Elaine N. Marieb
(Author), Katja N Hoehn (Author), Publication Date:
January 16, 2012
4.Hole’s
essentials of human anatomy and physiology. - 7th edition / David Shier,
Jackie, Ricki Lewis.
McGraw-Hill Companies, 2000.
5.Human
Anatomy and Physiology, 6th edition / Elaine Marieb
Seeley, Stephens, and Tate. Anatomy and Physiology, 5th
edition, McGraw-Hill Publishing, 2000.
6.Functional Human Anatomy / Edition 1, by David T.
Lindsay, Carol D. Rodgers, Jaci Vanheest, 1996 or newest
edition
7.Synopsis
of Human Anatomy And Physiology / Kent M. Van De Graaff , Stuart Ira Fox , Karen M. Lafleur // Mcgraw-Hill College
(December 10, 1996)
Optional
Textbook Supplements:
Miller-Keane. Encyclopedia and Dictionary of Medicine, Nursing, & Allied
Health, 6th edition, W. B. Saunders Company, 1997. Accompanying CD
Rom is REQUIRED.