Medial pterygoid muscle

The medial pterygoid is a thick, quadrilateral muscle located in the infratemporal fossa, on the medial surface of the mandibular ramus.

It mirrors the masseter muscle on the inner aspect of the mandible and, together with it, forms a muscular sling that elevates the mandible.

Anatomical details

1. Origin

• Deep head: Medial surface of the lateral pterygoid plate and the adjoining pyramidal process of the palatine bone.

• Superficial head: Maxillary tuberosity and the adjacent pyramidal process of the palatine bone.

2. Insertion

• Medial surface of the ramus and angle of the mandible, near the insertion of the masseter on the lateral side.

Innervation

Nerve to medial pterygoid, a branch of the mandibular division of the trigeminal nerve (CN V3).

• Note: This nerve also supplies the tensor tympani and tensor veli palatini muscles.

Actions

• Elevates the mandible (closes the mouth).

• Assists in protrusion of the mandible.

• Unilateral contraction produces small side-to-side (grinding) movements during chewing, acting alternately with the lateral pterygoid on the opposite side.

Clinical correlate

Mandibular nerve lesions: Weakness of the medial pterygoid muscle contributes to deviation of the jaw toward the affected side when opening.