The medial pterygoid is a paired primary muscle of mastication. It is a thick, short and quadrilateral-shaped muscle located in the infratemporal fossa of the skull.

Overall, it connects the maxilla, sphenoid and palatine bone with the mandible. The medial pterygoid is also known as the internal pterygoid muscle, as it lies medial to the lateral pterygoid muscle.

The medial pterygoid is composed of two heads - the superficial head and the deep head. Both heads have different origin sites, and the superficial head is smaller than the deep head.

Fibers of both heads pass inferior, lateral and posterior and insert on the inner surface of the mandibular angle and ramus via a strong tendinous lamina.

Origin: superficial head - maxillary tuberosity of the maxilla and the pyramidal process of the palatine bone; deep head - medial surface of the lateral pterygoid plate of the sphenoid bone.

Insertion: pterygoid tuberosity of the mandible, inner surface of the mandibular ramus.

Action: bilateral contractions - protrusion of the mandible (both muscles act together with the lateral pterygoids); these muscles also contribute to the elevation of the mandible (they act as synergists to the temporal and masseter muscles); unilateral contractions - side-to-side movement (rotation) of the mandible to the opposite side (muscle acts together with the lateral pterygoid of the same side).

Innervation: medial pterygoid nerve that is a branch of the mandibular division (CN V3) of the trigeminal nerve (CN V).

Blood supply: pterygoid arteries of the maxillary artery, muscular branches of the facial artery.

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Medial pterygoid muscle