The medial pterygoid muscle (or internal pterygoid muscle) is a thick, quadrilateral muscle of the face. It is supplied by the mandibular branch of the trigeminal nerve (V). It is important in mastication (chewing).

The medial pterygoid muscle consists of two heads. The bulk of the muscle arises as a deep head from just above the medial surface of the lateral pterygoid plate. The smaller, superficial head originates from the maxillary tuberosity and the pyramidal process of the palatine bone.

Its fibers pass downward, lateral, and posterior, and are inserted, by a strong tendinous lamina, into the lower and back part of the medial surface of the ramus and angle of the mandible, as high as the mandibular foramen. The insertion joins the masseter muscle to form a common tendinous sling which allows the medial pterygoid and masseter to be powerful elevators of the jaw.

The medial pterygoid muscle has functions including elevating the mandible (closing the mouth), protruding the mandible, mastication (especially for when the maxillary teeth and the mandibular teeth are close together),^[1] and excursing the mandible (contralateral excursion occurs with unilateral contraction).

• Position of medial pterygoid muscle (red).
• Left palatine bone. Posterior aspect. Enlarged.
• Mandible. Inner surface. Side view.
• Plan of branches of internal maxillary artery.
• Distribution of the maxillary and mandibular nerves, and the submaxillary ganglion.
• Mandibular division of trifacial nerve, seen from the middle line.
• Muscles of the pharynx, viewed from behind, together with the associated vessels and nerves.
• Deep dissection. Anterior view.

• Medial pterygoid muscle
• Medial pterygoid muscle
• Medial pterygoid muscle
• Medial pterygoid muscle
• Medial pterygoid muscle
• Infratemporal fossa. Lingual and inferior alveolar nerve. Deep dissection. Anterolateral view