Superior head of lateral pterygoid muscle

At a glance

English

Superior head of lateral pterygoid muscle

Latin (TA2)

Caput superius musculi pterygoidei lateralis

System

Muscle

Region

Head

Side

Paired, left and right

About the superior head of lateral pterygoid muscle

The lateral pterygoid sits in the infratemporal fossa, deep to the ramus of the mandible, and is the only one of the four muscles of mastication that helps to open the mouth rather than close it. It has two heads whose fibres run nearly horizontally back to the temporomandibular joint. The superior head is the smaller, upper one; its close link to the joint makes it of special interest in disorders of the jaw.

It springs from the downward-facing infratemporal surface of the sphenoid's greater wing, and from the crest that marks the edge of that surface. Its fibres run backwards and outwards, close under the roof of the fossa, to end on the front of the capsule of the temporomandibular joint and on the front edge of the articular disc inside it; some fibres join the inferior head at the pterygoid fovea on the mandibular neck. A small gap separates the two heads, and the maxillary artery commonly runs between or across them.

Its role differs from that of the inferior head. Recordings of muscle activity show that the superior head works chiefly during closing movements and clenching, especially on the side of the bite, when it steadies the disc and condyle against the slope of the articular eminence. In this way it controls the backward glide of the disc as the jaw closes, while the inferior head drives forward movement of the condyle in opening and protrusion. Together, the two heads keep disc and condyle moving as a unit.

It is supplied by the nerve to lateral pterygoid from the mandibular division of the trigeminal nerve, and by pterygoid branches of the maxillary artery. Because it attaches to the disc, faulty action of this head has been suggested as one cause of clicking and displacement of the disc in temporomandibular disorders, although its exact contribution remains debated.

Attachments, action and supply

Origin

Greater wing of the sphenoid: its infratemporal surface and the crest bounding it.

Insertion

Capsule and articular disc of the temporomandibular joint, with some fibres to the pterygoid fovea of the mandibular neck.

Action

Steadies the articular disc and condyle against the articular eminence, mainly during closing and clenching; assists the inferior head in protrusion.

Nerve supply

Nerve to lateral pterygoid, from the mandibular division of the trigeminal nerve (V3).

Blood supply

Pterygoid branches of the maxillary artery.