Table 2.

Equine thoracic limb extrinsic muscles and their primary biomechanical functions as reported in Sisson & Grossman (1975), Nickel et al. (1986) and Dyce et al. (1996)

Muscle	Origin	Insertion	Function
Trapezius cervicis	Ligamentum nuchae from C2 to T10/11	Spine of scapula	Scapular elevation and limb protraction
Trapezius thoracis	Ligamentum nuchae from C2 to T10/11	Spine of scapula	Scapular elevation and limb retraction
Rhomboideus cervicis	From C2 to T7/8	Medial aspect of scapula cartilage	Scapular elevation and limb protraction
Rhomboideus thoracis	From C2 to T7/8	Medial aspect of scapula cartilage	Scapular elevation and limb retraction
Latissimus dorsi	From supraspinous ligament via a broad aponeurosis stretching from T3/4 to L5 and from the thoraco-lumbar fascia	Medial aspect of teres tubercle with tensor fascia antibrachii and teres major	Limb retraction, when limb fixed advances trunk
Omotransversarius	Fascia of lateral shoulder region	By separate digitations onto transverse processes of C2–4	Limb protraction and lateral flexion of neck
Brachiocephalicus cranial and caudal	Mastoid process and transverse processes of varying proximal cervical vertebrae	Deltoid tuberosity between biceps brachii and brachialis	Limb protraction and lateral flexion of neck towards active side
Subclavius	Lateral aspect of sternum from costal cartilages 1–4	Lateral tuberosity of humerus	Adduction and retraction of limb
Pectoralis profundus	Lateral sternum, cartilages and distal extremities of ribs 4/5–9	Medial tuberosity of humerous & insertion ofbiceps brachii. Some fibres fuse with the tendonsheet of coracobrachialisand supraspinatus then pass onto lateral tuberosity of humerus	Adduction and retraction of limb
Pectoralis transversus	Ventral aspect of sternum between 1st and 6th costal cartilages	Antibrachial fascia	Adduction and protraction of the limb
Pectoralis descendens	Lateral aspect of manubrium sternum	Brachial fascia and crest of humerus with brachiocephalicus	Adduction and protraction of the limb
Serratus ventralis cervicis	Transverse processes of C3/4–C7	Deep surface of scapula and cranial aspect of scapula cartilage	Suspends limb from trunk, raises thorax, retraction of limb via scapular rotation
Serratus ventralis thoracis	Middle section of ribs 1–8/9	Deep surface of scapula and caudal aspect of scapula cartilage	Suspends limb from trunk, raises thorax, limb protraction via scapular rotation