Overview
In ruminants it is large and made up of several layers separated by tendinous sheets, grouped into a superficial and a deep part. The bovine mandible is narrower than the upper jaw, so the cheek teeth meet on one side at a time. Chewing, including rumination, is a lateral grinding stroke in which the masseter plays a leading role.
Origin
Facial tuber (tuber faciale) of the maxilla and zygomatic arch.
Insertion
Lateral surface of the mandibular ramus and its caudal ventral border, as far as the angle.
Action
Elevates the mandible and closes the mouth. Contraction on one side shifts the mandible towards that side and produces the grinding stroke.
Innervation
Masseteric nerve, from the mandibular nerve (cranial nerve V).
Clinical relevance
- Atrophy limited to one side suggests a lesion of the mandibular nerve on that side.
- In bovine meat inspection the masseters are incised to look for cysts of Cysticercus bovis, the larval stage of Taenia saginata.