Overview
In the dog it is the largest of the masticatory muscles. It covers the lateral surface of the cranial vault and passes medial to the zygomatic arch to the mandible.
Origin
Temporal fossa, external sagittal crest and nuchal crest.
Insertion
Coronoid process of the mandible.
Action
Elevates the mandible and closes the mouth.
Innervation
Mandibular nerve (n. mandibularis), a branch of the trigeminal nerve (cranial nerve V).
Clinical relevance
Masticatory muscle myositis is an autoimmune disease against type 2M fibres, which only these muscles have. In the acute phase it causes pain and inability to open the mouth; in the chronic phase, marked atrophy of the temporalis and masseter.