Overview
It has a cervical part (pars cervicalis) and a thoracic part (pars thoracica). In cattle it is well developed and crossed by tendinous sheets that let it bear weight passively. Cattle have no clavicle, so the thoracic limb does not articulate with the trunk: it is attached by a synsarcosis, of which the serratus ventralis is the main component. Together with the pectorals it forms the thoracic sling, from which the trunk hangs between the two scapulae.
Origin
- Cervical part: transverse processes of the caudal cervical vertebrae.
- Thoracic part: first ribs, by digitations alternating with those of the external abdominal oblique.
Insertion
Serrated face (facies serrata), on the dorsal part of the medial surface of the scapula, and the scapular cartilage.
Action
Supports the trunk and moves the scapula. The cervical part draws the dorsal angle of the scapula cranially and the thoracic part caudally. With the limb fixed, the thoracic part assists inspiration.
Innervation
Ventral branches of the cervical nerves (cervical part) and long thoracic nerve (n. thoracicus longus) for the thoracic part.