Extrinsic Muscles of Thoracic Limb

Superficial Pectoral Origin

Descending: 1st sternebrae

Transverse: 1-3rd sternebrae

Superficial Pectoral Inserts

Whole crest of Greater tubercle of Humerus.

Superficial pectoral Action

Wt: Abduct the limb Non-Wt: Prevent abduction

Superficial pectoral Innervation

Ventral branch C7, C8.

Deep pectoral Origin

Ventral sternum, Fibrous raphe between muscles; Deep abdominal fascia region of xiphoid cartilage.

Deep pectoral Insert

Major portion lesser tubercle; Aponeurosis greater tubercle/crest.

Deep pectoral Action

Wt: pull trunk cranially, extend shoulder Non-Wt: push trunk caudally, flex shoulder

Deep pectoral Innervation

Innervation: Caudal pectorals; C8, T1.

Brachiocephalicus Origin

Distal 1/3 of humerus; Clavicle

Brachiocephalicus Insert

Cleidobrachialis, Distal cranial humerus.

Brachiocephalicus Action

Advance limb; Extend shoulder joint, draw neck cranially to side.

Brachiocephalicus Innervation

Accessory nerve & ventral branches of cranial nerves.

Sternocephalicus Origin

First Sternebra/manubrium

Sternocephalicus Insert

Mastoid part of temporal bone; Nuchal crest of occipital bone.

Sternocephalicus Action

Draw head & neck to the side.

Sternocephalicus Innervation

Accessory nerves & ventral branch of cervical spinal nerves.

Sternohyoideus Origin

First Sternebrae & costal cartilage

Sternohyoideus Insert

Basihyoid Bone.

Sternohyoideus Action

Pull tongue & larynx caudally.

Sternohyoideus Innervation

Ventral branches of cervical spinal nerves.

Sternothyroideus Origin

First costal cartilage.

Sternothyroideus Insert

Caudolateral surface of thyroid

Sternothyroideus Action

Draw tongue & larynx caudally.

Sternothyroideus Innervation

Ventral branches of cervical spinal nerves; Hypoglossal nerve.

Omnotransversarius Origin

Distal spine of scapula; Cranially transverse process of atlas.

Omnotransversarius Action

Advance neck laterally.

Omnotransversarius Innervation

Accessory nerve.

Trapezius Origin

Median raphe of neck & supraspinous ligament at 3rd level-9th level cervical & thoracic vertebrae.

Trapezius Insert

Spine of scapula.

Trapezius Action

Elevate & abduct forelimb.

Trapezius Innervation

Accessory nerve.

Rhomboideus Origin

Cervical: median raphe of neck;

Capitis: nuchal crest of occipital bone; spinous process of 7 thoracic vertebrae.

Rhomboideus Insert

Dorsal border & adjacent structures of scapula.

Rhomboideus Action

Elevate forelimb & draw scapula to trunk.

Rhomboideus Innervation

Ventral branches of cervical spinal nerves.

Latissimus dorsi Origin

Origin: Thoracolumbar fascia of lumbar; last 7-8 thoracic vertebrae.

Latissimus dorsi Insert

Teres major tuberosity of humerus; Teres major tendon.

Latissimus dorsi Action

Draw free limb caudally; Flex shoulder.

Latissimus dorsi Innervation

Thoracolumbar nerves C7, C8, T1.

Serratus ventralis Origin

Cervical: transverse process of last 5 cervical vertebrae; Thoracic: first 7-8 ribs

Serratus ventralis Insert

Ventral middle; Dorsomedial third of scapula (Serrated).

Serratus ventralis Action

Support trunk; Depress scapula.

Serratus ventralis Innervation

Ventral branch of cervical spinal nerves, long thoracic nerve.