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 of biceps brachii. Some fibres fuse with the tendon sheet of coracobrachialis and 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 |