Medial pterygoid muscle

At a glance

English

Medial pterygoid muscle

Latin (TA2)

Musculus pterygoideus medialis

System

Muscle

Region

Head

Side

Paired, left and right

About the medial pterygoid muscle

The medial pterygoid is one of the four muscles of mastication. It is a thick, quadrilateral muscle lying on the inner surface of the ramus of the mandible, in the infratemporal fossa, and it mirrors the masseter, which lies on the outer surface of the same bone. Between them the two muscles cradle the angle of the jaw.

It has two heads that embrace the lower head of the lateral pterygoid. The deep head, which forms most of the muscle, comes from the inner face of the lateral pterygoid plate and the pterygoid fossa between the two plates. The smaller superficial head arises lower and further forward, from the tuberosity of the maxilla and the palatine bone's pyramidal process. The fibres run downwards, backwards and outwards and attach by a strong tendinous sheet to the rough inner face of the mandibular ramus near its angle, from the angle up as far as the mandibular foramen. At the lower border its tendon joins that of the masseter, forming a muscular sling that holds the angle of the jaw from both sides. The lingual and inferior alveolar nerves descend on its outer surface, between it and the ramus.

With the masseter and temporalis it raises the mandible to close the mouth and gives a strong grinding bite, especially when the teeth are nearly together. It also helps to push the jaw forwards, with the lateral pterygoid. When one side acts alone with the lateral pterygoid of the same side, the chin swings to the opposite side; alternating these movements produces the side-to-side action of chewing.

It is supplied by the nerve to medial pterygoid, which leaves the main trunk of the mandibular nerve before it divides. That small nerve also supplies tensor veli palatini and tensor tympani, unlike the nerves to the other chewing muscles, which come from the anterior division. Its blood comes from pterygoid branches of the maxillary artery. Spasm of the muscle, for example from an infection around a wisdom tooth or after an inferior alveolar nerve block, limits mouth opening, a condition called trismus.

Attachments, action and supply

Origin

Deep head: inner face of the lateral pterygoid plate and pterygoid fossa. Superficial head: maxillary tuberosity and the palatine bone's pyramidal process.

Insertion

Inner face of the mandibular ramus and angle, up to the mandibular foramen.

Action

Elevates the mandible; helps protrude it; acting on one side, swings the chin to the opposite side in grinding.

Nerve supply

Nerve to medial pterygoid, from the main trunk of the mandibular nerve (V3).

Blood supply

Pterygoid branches of the maxillary artery.