Overview
Flat, elongated neck muscle lying between the trapezius (dorsal) and the brachiocephalicus (ventral). It is one of the muscles that attach the thoracic limb to the trunk. In the horse it is thin and partly fused with the cleidomastoideus, which covers its cranial part, so the two are hard to separate in dissection.
Origin and insertion
- In the neck: transverse processes of the cranial cervical vertebrae.
- At the shoulder: fascia of the shoulder region, over the scapular spine.
Action
Draws the thoracic limb cranially. With the limb planted, it bends the neck towards the contracting side.
Clinical relevance
Together with the brachiocephalicus it covers the superficial cervical lymph nodes, cranial to the shoulder. In the horse they lie fairly deep and are harder to palpate than in cattle.