MUSCLES OF THE PECTORAL GIRDLE

Question 1

M. trapezium

Answer 1

This thin, flat, triangular muscle lies superficially in the dorsal neck and interscapular regions. It is divided into cervical and thoracic parts by a vertically orientated fibrous band. The fibres of the Pars cervicalis run caudo-ventrally, while those of the Pars thoracica run cranio-ventrally.

Question 2

M. trapezium Origin?

Answer 2

Cervical part: Median fibrous raphe of the neck, as far cranially as C3. Thoracic part: Lig. supraspinale as far caudally as T9.

Question 3

M. trapezium Insertion?

Answer 3

Cervical part: The length of the Spina scapulae, except for a small portion ventrally.
Thoracic part: The dorsal third of the scapular spine.

Question 4

M. trapezium Function?

Answer 4

The Pars cervicalis moves the ventral angle of the scapula cranially and thus advances the limb.
The Pars thoracica rotates the scapula caudally and retracts the limb. Both parts acting together raise the scapula against the trunk and lift the limb

Question 5

M. latissimus dorsi

Answer 5

This broad, flat, roughly triangular muscle covers the lumbar region dorsally and the thorax
laterally. Its cranial edge covers the caudal angle of the scapula and holds it against the thorax.

Question 6

M. latissimus dorsi Origin?

Answer 6

A broad aponeurosis from the superficial thoracolumbar fascia and the lateral surfaces of the last three ribs

Question 7

M. latissimus dorsi Insertion?

Answer 7

Tuberositas teres major (together with the M. teres major and M. cutaneus trunci) and the fascia on the medial surface of the M. triceps brachii Caput
longum

Question 8

M. latissimus dorsi Function?

Answer 8

Retraction of the free limb and flexion of the shoulder (it is thus an antagonist. if the thoracic limbs are fixed in extention bilateral contraction draws the trunk forward and flexes the back.

Question 9

M. rhomboideus

Answer 9

The rhomboideus muscle lies dorso-laterally on the neck and cranial thorax. It lies deep to the M. trapezium and connects the dorsal borders of the scapulae. The muscle has three parts, which, although intimately fused, are regarded as separate muscles; they are the M. rhomboideus capitis / cervicis / thoracis. The cervical and thoracic components form the bulk of the muscle; the M. rhomboideus capitis is a narrow band given off by the cervical rhomboid muscle. Functionally, the three muscles are regarded as a single unit

Question 10

M. rhomboideus origin?

Answer 10

M. rhomboideus capitis: The lateral edge of the M. rhomboideus cervicis at about the level of C4.
M. rhomboideus cervicis: Median fibrous raphe of the neck (as far cranially as C2) and the spinous processes of T I -T3. M. rhomboideus thoracis: Spinous processes of T4-T7

Question 11

M. rhomboideus Insertion?

Answer 11

M. rhomboideus capitis: Crista nuchae (caudal aspect of the skull).
M. rhomboideus cervicis: Scapula, medially on the dorsal margin.
M. rhomboideus thoracis: Scapula, medially on the dorsal margin and a small area laterally, just cranial to the caudal angle.

Question 12

M. rhomboideus Function?

Answer 12

Advances or retracts the limb (depending on the limb’s position when the muscle contracts); elevation of the scapula and limb. When the limbs are fixed,
bilateral contraction stabilizes the head and extends the neck, while unilateral contraction flexes the neck laterally.

Question 13

M. brachiocephalicus

Answer 13

Although this long, flat muscle is divided into two main components by the Intersectio
clavicularis, it functions as a single muscle. The distal component is the M. cleidobrachialis,
while the proximal component is the M. cleidocephalicus.

Question 14

M. cleidobrachialis

Answer 14

At its origin, this muscle lies caudal to the M. sternocephalicus and cranial to the acromial part of
the M. deltoideus; it passes distally, between the M. biceps brachii (medial) and the M. brachialis
(lateral), and inserts on the humerus. The M.cleidobrachialis is regarded as once having been the
clavicular part of the deltoid muscle. Its appropriation by the cleidocephalic muscle probably accompanied the evolution of quadrupedal posture.

Question 15

M. cleidobrachialis origin insertion and function?

Answer 15

Origin: Intersectio clavicularis.
Insertion: Crista humeri.

Question 16

M. cleidocephalicus

Answer 16

This muscle has a superficial cervical part and a deep mastoid part:
The Pars cervicalis is a wide, thin muscle, which extends to the dorsal neck.It lies caudal to the M.sternocephalicus Pars occipitalis and cranial to the M. trapezium.
The Pars mastoidea is a well developed, round muscle bundle, which is usually split longitudinally into two bellies. Originating from the deep surface of the clavicular intersection, it extends to the skull lying deep to the M. cleidocephalicus Pars cervicalis, M. omotransversarius and M. sternocephalicus Pars occipitalis

Question 17

M. cleidocephalicus origin insertion?

Answer 17

Origin: Intersectio clavicularis.
Insertion: Cervical part: Crista nuchae and the median fibrous raphe of the neck. Mastoid part: Mastoid process of the temporal bone, together with the mastoid part of the M. sternocephalicus.

Question 18

M. cleidocephalicus function?

Answer 18

Unilateral contraction advances the limb. With the limbs fixed, bilateral contraction flexes the neck, while unilateral contraction flexes the neck laterally

Question 19

M. omotransversarius

Answer 19

This flat, narrow muscle can be seen at the ventral end of the scapular spine, cranio-ventral to the M. trapezium Pars cervicalis and caudal to the M. cleidocephalicus Pars cervicalis. The greater (cranial) part of the muscle lies deep to the M. brachiocephalicus.

Question 20

M. omotransversarius function?

Answer 20

Function: To advance the limb. When the limbs are fixed, bilateral contraction flexes the neck, while unilateral contraction flexes the neck laterally.

Question 21

M. omotransversarius origin and intsertion?

Answer 21

Origin: The ventral part of the scapular spine.
Insertion: Wing of the atlas.

Question 22

who are the Mm. pectorales superficiales?

Answer 22

Together with the deep pectoral muscle, the superficial pectoral muscles form a strong ventral connection between the trunk and thoracic limb. There are two superficial muscles, the M. pectoralis descendens and the M. pectoralis transversus:

Question 23

M. pectoralis descendens

Answer 23

This muscle lies superficially on the ventral surface of the transverse pectoral muscle. It is a
relatively narrow bundle, approximately one third the width of the transverse pectoral. It passes
between the M. biceps brachii and M. brachialis and inserts on the humerus, just proximal to the
insertion of the M. cleidobrachialis.

Question 24

M. pectoralis descendens oridin and insertion?

Answer 24

Origin: Manubrium sterni.
Insertion: Distal portion of the Crista tuberculi majoris of the humerus, together with the
transverse pectoral muscle

Question 25

M. pectoralis descendens function?

Answer 25

Function: Protraction or retraction (depending on the limb’s initial position) and adduction
of the limb.

Question 26

M. pectoralis transversus

Answer 26

This broad, well-developed muscle lies deep to the narrow M. pectoralis descendens. It sweeps towards the cranial aspect of the humerus without impinging on the axilla (see below).

Question 27

M. pectoralis transversus origin?

Answer 27

Origin: Ventral aspect of the sternum, from themanubrium to the third costal cartilage.

Question 28

M. pectoralis transversus insertion?

Answer 28

Distal portion of the Crista tuberculi majoris of the humerus, together with the descending pectoral muscle.

Question 29

M. pectoralis transversus function?

Answer 29

Protraction or retraction (depending on the limb’s initial position) and adduction.

Question 30

M. pectoralis profundus

Answer 30

This broad, powerful muscle is also known as the ascending pectoral muscle. It covers the sternum and costal cartilages ventrally, but is separated from them by the aponeurotic tendon of origin of the M. rectus abdominis. מפה לא חשוב Apart from the main muscle mass, a minor superficial, lateral part can also be identified.

Question 31

M. pectoralis profundus origin?

Answer 31

Origin: The sternum, on the ventral midline (main part); abdominal fascia (minor part) החלק הקטן לא חשוב.

Question 32

M. pectoralis profundus insertion?

Answer 32

Main part: This inserts principally on the Tub. minus of the humerus, it also sends a band of muscle and aponeurosis over the proximal M. biceps brachii to insert on cranio-medial aspect of the Tub. majus, and on the proximal portion of the Crista tuberculi majoris. The aponeurosis helps to hold the biceps in position.
לא חשוב: Minor part: This blends with the fascia on the medial aspect of the brachium.

Question 33

M. pectoralis profundus function?

Answer 33

Extension of the shoulder; retraction and adduction of the limb. While running, when the limbs are fixed in extension, bilateral contraction advances the trunk.
Since the muscle’s insertion is considerably more dorsal than its origin it slings and supports the trunk between the limbs (together with the M. serratus ventralis).

Question 34

M. serratus ventralis

Answer 34

This large, powerful, fan-shaped muscle has cervical (M. serratus ventralis cervicis) and thoracic (M. serratus ventralis thoracis) components. Similar to the deep pectoral muscle, this muscle inserts considerably dorsal to its origins and plays a major part in supporting the weight of the trunk between the limbs.

Question 35

M. serratus ventralis origin?

Answer 35

Cervical part: Transverse processes of C3-C7.
Thoracic part: Lateral surfaces of ribs 1-8. Caudally, the muscle bundles interdigitate with the most cranial insertions of the M. obliquus externus abdominis.

Question 36

M. serratus ventralis insertion?

Answer 36

Facies serrata of the scapula

Question 37

M. serratus ventralis function?

Answer 37

Suspension of the trunk. The cervical part inserts cranio-dorsal to the scapula’s axis of rotation; it therefore retracts the limb. The thoracic part inserts caudo-dorsal to the axis and advances the limb. With the limbs fixed, unilateral contraction of the cervical part flexes the neck laterally; bilateral contraction lifts the neck. The thoracic part is potentially a muscle of inspiration when the limbs are abducted.