Extrinsic Muscles of the Thoracic Limb

Question 1

superficial pectoral m.

Answer 1

O: first three sternebrae; median fibrous raphe at the ventral midline

I: crest of the greater tubercle of the humerus

Action: adduct limb (weight bearing); prevent abduction (non weight bearing)

Question 2

deep pectoral m.

Answer 2

O: ventral part of the sternum; median fibrous raphe at the ventral midline

I: greater tubercle and crest of the humerus through aponeuroses; lesser tubercle of the humerus

Action: pull the trunk cranially when advancing; pull the limb caudally when not supporting weight

horse has a subclavius muscle

Question 3

brachiocephalicus

Answer 3

O: clavicular intersection

I: distal end of the cranial humerus (cleidobrachialis); mid dorsal fibrous raphe of the neck (cleidocervicalis/pars cervicis); mastoid part of the temporal bone (cleiodmastoideus/pars mastoid)

Action: draw the head and neck to one side; advance the limb; extend the shoulder

**Horse: one part of cleidocephalicus=cleidomastoideus; instead of sternocephalicus, they have a sternomandibularis

***ox and goat: cleido-occipitalis + cleidomastoideus=cleiodcephalicus

*dorsal boundary of jugular groove

Question 4

omotransversarius m.

Answer 4

O: wing of atlas (transverse process)

I: distal end of the spine of the scapula

Action: flex the head and neck laterally; advance limb

superficial cervical lymph node

Question 5

trapezius m.

Answer 5

O: median fibrous raphe of the neck; supraspinous ligament
cervical and thoracic trapezius

I: spine of scapula

Action: elevate and abduct limb

Question 6

rhomboideus m.

Answer 6

rhomboideus cervicis
rhomboideus capitis
rhomboideus thoracis

O: spinous process of the thoracic vertebrae (thoracis); base of skull (capitis); median fibrous raphe of neck (cervicis)

I: dorsal border of scapula

Action: elevate limb; draw scapula against trunk

Question 7

latissimus dorsi m.

Answer 7

O: thoracolumbar fascia; last few ribs

I: teres major tuberosity via teres major tendon

Action: draw limb caudally (when digging); flex shoulder

Question 8

serratus ventralis

Answer 8

serratus ventralis cervicis and thoracis

O: ribs (thoracis); transverse process of cervical vertebrae (cervicis)

I: serrated face of scapula

Action: depress scapula; support trunk

flying scapula