Muscles of the Thoracic Limb
muscles of the shoulder girdle
The
muscles of the shoulder girdle are in dorsal and ventral group which
attached the thoracic limb to the head, neck
and trunk. The dorsal cervical muscles are located on each side of the
nuchal ligament.
- The superficial layer is formed by the
trapezius and omotransversarius.
- The second layer comprises the rhomboideus
and serratus ventralis cervicis.
- The third layer corresponds to the
splenius.
- The fourth layer includes the semispinalis
capitis and intertransversarii cervicis.
- The fifth layer consists of the spinalis
and semi-spinalis.
- The sixth layer, which is on the median plane, is formed by the nuchal ligament.
NUCHAL LIGAMENT
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dorsal division
1. Trapezius: (cervical & thoracic)
Trapezius is wide, undivided, flat and triangular muscle. The base extends along the nuchal and supraspinous ligament, where it originates from the atlas to the 12th or 13th thoracic vertebrae. Some authors recognize a cervical and thoracic part, although there is no separation in the continuity of the muscle tissue.
Cervical part
Origin:- 2nd cervical vertebra to the level of 1st or 2nd thoracic vertebra.
Insertion: - The scapular spine.
Thoracic part
Origin:- The spine of all thoracic vertebrae. (sheep- 11th
or 12th thoracic vertebrae)
Insertion:- The scapular spine.
Action:- The thoracic part draws the scapula caudad and
dorsad.
The cervical part pulls the
scapula craniad and dorsad, or it may incline the head
and neck laterally.
Acting together the muscles serve to lift the scapula dorsad.
Blood supply:- Vertebral, deep cervical, dorsal scapular and dorsal intercostal
arteries.
Nerve
supply:- The dorsal branch of accessory nerve.
2. Omotransversarius: (cervical)
Omotransversarius
is located on the lateral surface of the neck, extending from the
wing of the atlas to the shoulder.
Origin:- The wings of the atlas.
Insertion:- The scapular spine.
Action :-
To move the head and neck laterally.
To
draw the shoulder and limb craniad.
Blood
supply:- Vertebral and superficial cervical
arteries.
Nerve
supply:- Cervical and accessory nerves.
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3. Rhomboideus: (cervical & thoracic)
Rhomboideus arises on the nuchal ligament from the 2nd cervical to the 5th thoracic vertebrae. A definite division into cervical and thoracic muscles is lacking but, for convenience two parts are frequently recognized.
Cervical part
Origin:- 2nd
cervical to the 2nd thoracic
vertebra.
Insertion:- Cranio-medial surface of the scapular cartilage.
Thoracic part
Origin:- 2nd to
5th thoracic spine.
Insertion:- Caudo-medial surface of the scapular cartilage.
Action:- The thoracic part
draws the scapula dorsally and medially.
The cervical part draws the scapula dorsally and cranially.
Blood supply:- Branches of the deep
cervical and dorsal scapular arteries .
Nerve supply:- Branches of
cervical and thoracic spinal nerves.
4. Serratus ventralis: (cervical & thoracic)
Serratus ventralis is a large, fan-shaped muscle, located on the lateral surface of the neck and thorax. It receives its name from the serrated ventral edge of its thoracic portion. It consists of cervical and thoracic parts.
Cervical part (serratus cervicis)
Origin: The transverse
processes of the last four or five cervical vertebrae.
Insertion: A large triangular
area on the cranio-dorsal part of the costal surface of the
scapula and the adjacent part of the cartilage.
Thoracic part (serratus thoracis)
Origin:- Lateral surfaces
of the thorax on the first eight or nine ribs.
Insertion:- On the muscular
line of the scapula on the caudo-dorsal part, the caudal angle
of scapula and the adjacent part of the cartilage.
Action:- The cervical
portion pulls the limb craniad.
The thoracic portion pulls the limb caudad.
Blood supply:- Costo-cervical,
deep cervical, vertebral artery.
Nerve supply:- Fifth to eighth
cervical spinal nerves.
5. Splenius: (cervical & capitis)
Splenius is relatively thin, large, flat triangular muscle which lies on the lateral surface of the neck dorsal to the level of the cervical vertebrae.
Origin:- It arises from
the spinous processes of the first three or four thoracic spine to the
3rd cervical
vertebra.
Insertion:- Wing of atlas,
transverse process of axis and 3rd cervical vertebra.
The fiber also insert on the occipital bone(splenius capitis).
Action:- To elevate the head and neck.
Blood supply:- Costo-cervical,
deep cervical, vertebral artery.
Nerve supply:- Dorsal branch of
cervical nerves.
6. Semispinalis: (cervical, thoracic & capitis)
Semispinalis capitis is the largest muscle dorsal to the cervical vertebrae, arises from 9th or 10th thoracic vertebrae.
Origin:- The transverse
process of the first ten thoracic vertebrae,
the articular processes of the
last five cervical vertebrae, and
the nuchal ligament.
Insertion:- The occipital
bone near the attachment of the funicular part of the nuchal
ligament.
Action:- Acting singally, to turn and raise the head; together, to extend the head.
Blood supply:- Deep cervical
artery, vertebral and dorsal intercostal arteries.
Nerve supply:- Dorsal branches
of the thoracic and cervical spinal nerves.
7. Intertransversarii cervicis: (dorsal & ventral part)
Intertransversarii cevicis occupy the spaces between the articular and transverse processes on the lateral surface of the cervical vertebrae.
Origin & Insertion:- Specific origins and insertions are not recognized.
Action:- To flex the neck laterally.
Blood supply:- Vertebral artery.
Nerve supply:- Ventral branches
of the cervical spinal nerves.
8. Latissimus dorsi: (thoracic & lumbar)
Latissimus dorsi is flat, relatively thin and triangular that covers much of the lateral surface of the thorax.
Origin:- 4th
thoracic to last lumbar spine.
Insertion:- The teres tuberosity.
Action:- It draws the trunk cranially.
Blood supply:- Thoraco-dorsal and
dorsal intercostal arteries.
Nerve supply:- Thoraco-dorsal
nerve.
VENTRAL
DIVISION
1. Brachiocephalicus:
Brachiocephalicus is a thin muscle which extends along the sides of the neck from the head to the arm. It is incompletely divisible into two portions.
A.
Cleidocephalicus
Cleido-occipitalis
Cleido-mastoideus
B.
Cleidobrachialis-
fuses caudally with cleido-mastoideus to form a
ventral thick
muscle which attaches to the humerus
upon the humeral crest of the groove for the brachialis
Origin:- The
cleido-occipitalis arises from occipital bone and the nuchal ligament.
The cleido-mastoideus(smaller)
arises from the mastoid process of temporal
bone.
Insertion:- Crest of humerus, distal to the deltoid tuberosity.
Action:- It draws the limb craniad or inclines the head and neck laterally.
Blood supply:- Deep cervical, superficial
cervical, and vertebral arteries.
Nerve supply:- Cervical spinal, accessory, and axillary nerves.
Note:- Slightly dorsal
to the level of the shoulder joint, the brachiocephalicus presents a fibrous
intersection(intersection clavicularis) which is a remnant of the clavicle.
2. Pectoralis superficialis:
Pectoral
superficialis
extends from the ventral and cranial parts of the sternum to the medial surface
of the arm and fore-arm. It is less divided in ruminant than in the horse, and
its two parts are not as distinct as horse.
Pectoralis descendens
Origin:- First sternebra
to the humerus.
Insertion:- On the crest of
humerus, in common with cleidobrachialis.
Action:- Adduction of the
limb.
Blood supply:- External thoracic
arteries.
Nerve supply:- cranial pectoral
nerves.
Pectoralis transversus
Origin:- First to fourth
or sixth sternal segment.
Insertion:- Medial aspect of
fore-arm.
Action:- Adduction of the
limb.
Blood supply:- External thoracic
and collateral ulnar arteries.
Nerve supply:- cranial pectoral
nerves.
Pectoralis ascendens
Origin:- Ventral surface
of sternum from a median raphe.
Insertion:- The lesser and
greater tubercle of humerus.
Action:- To retract the
limb or the trunk may be pulled craniad as in walking.
Blood supply:- External thoracic
arteries.
Nerve supply:- cranial pectoral
nerves.
3. Subclavius:
It is very
prominent in the goat and also present in sheep. In the ox, a small round
bundle of fleshy fibers arises from the cartilage and ventral end of the first
rib, and is inserted on the deep face of the brachiocephalicus cranial to the
shoulder joint.
Origin:- Sternal end of
the cartilage of the first rib.
Insertion:- Medial surface of
the brachiocephalicus, in the vicinity of the clavicular
Intersection.
Action:- Adduction of the limb.
Blood supply:- Superficial
cervical artery.
Nerve supply:- Cranial pectoral nerve.
NUCHAL LIGAMENT
The nuchal ligament is a powerful elastic apparatus, which extends from the occipital bone to the wither. It is better develop in case of ox.
- The funicular part is clearly divided into two lateral halves, which are round at their occipital attachment, but from the axis caudally becomes rapidly wider and flat.
- This wide portion is almost sagittal, lies on either side of the vertebral spines, and is covered by the trapezius and rhomboideus muscles.
- From the highest part of the withers(third thoracic spine), it gradually diminishes in size and fades out in the lumbar region.
- The lamellar part is thick and consists of cranial and caudal parts. The cranial part is double; its fibers proceed from the funicular part the 2nd, 3rd and 4th cervical spines.
- The caudal part is single; its fibers extend from the 1st thoracic spine to the 5th, 6th and 7th cervical spines.
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