Thoracic Limb Extrinsic Muscles

Superficial fascia

Superficial fascia

The superficial fascia is deep to the skin and is therefore also referred to as subcutaneous fascia or subcutis. This is the connective tissue layer that attaches the skin to the underlying structures and is primarily collagen with some elastic tissue and a variable amount of fat.

Deep fascia

Same thing as superficial fascia just deep to it

Trapezius m.

O: Dorsal median raphe of neck and trunk (ca. C3 to T9)
I: Spine of scapula

N: Accessory n.
A: Elevation and abduction of thoracic limb

Rhomboideus m.

O: Nuchal crest of occiput (capitis), dorsal median raphe of neck and spinous processes of T1-3 (cervicis), and spinous processes of T4-T6/7 (thoracis)
I: Dorsal border of scapula

N: Cervical and thoracic spinal nerves

A: Elevate the limb, draw scapula to body wall

Brachiocephalicus m.

O: Dordal median raphe of neck & mastoid process of the skull (cleidocephalicus m.); Cranial aspect of the distal humerus (cleidobrachialis m.)

N: Cervical spinal nn., accessory n.

A : Advance limb, extend shoulder, laterally flex neck

Cleidobrachialis m.

O: Clavicular intersection
I: Cranial aspect of distal humerus

N: Ventral brr. of cervical spinal nn. accessory n.
A: Advance limb, extend shoulder, lateral flexion of neck (unilateral action) or fixation of neck (bilateral action)

Cleidocephalicus m.

O: Clavicular intersection
I: Dorsal median raphe of the neck & the mastoid process of skull
N: Ventral brr. of cervical spinal nn., accessory n.

A: Advance limb, extend shoulder, lateral flexion of neck (unilateral action) or fixation of neck (bilateral action)

Clavicular intersection

Brachiocephalicus m. has a clavicular intersection (tendon), the connective tissue remnant of the clavicle between the two sections.

Omotransversarius m.

O: Distal scapular spine
I: Wing of atlas

N: Branches from accessory n.
A: Draw limb craniad

Superficial pectoral m.

O: Cranial sternum to about the 3rd costal cartilage
I: Cranial edge of humerus on a line running distad from the greater tubercle to about the midpoint of the bone

N: Cranial pectoral nn., cervical nn. 7 & 8
A: Adduction of limb; advancement or retraction of the limb, depending on starting position and whether or not the limb is weight-bearing

Deep pectoral m.

O: Sternum and median raphe
I: Lesser and greater tubercles of humerus, medial brachial fascia

N: Caudal pectoral nn. (C8, T1)
A: Draw limb caudad, extend shoulder (can flex shoulder when limb not weight-bearing)

Cutaneus trunci m.

On skin for dissections in class

O: Superficial fascia of trunk
I: Caudal border of deep pectoral muscle & fascia of medial brachium

N: Lateral thoracic nerve
A: Twitch of skin

Latissimus dorsi m.

O: Thoracolumbar fascia
I: Via an aponeurosis to the tendon of the m. teres major and m. pectoralis profundus.

N: Thoracodorsal n. (C7-8, T1)
A: Adduct limb, draw limb caudad, flex shoulder; when limb is fixed in weight-bearing, draws the trunk forward

Serratus ventralis m.

O: Transverse processes of C3 – 7, ventral halves of ribs 1 – 7/8
I: Serrated face of the scapula

N: Long thoracic n., ventral brr of cervical spinal nerves
A: Support of the trunk; when the limb is in swing phase of gait, different groups of fascicles are capable of advancing or retracting the scapula and shoulder relative to the trunk; with the limb in stance phase of gait, the muscle can bring the trunk forward or back relative to the stationary foot

Subclavius m. (Eq, Bov.)

Identify it