Inferior head of lateral pterygoid muscle

At a glance

English

Inferior head of lateral pterygoid muscle

Latin (TA2)

Caput inferius musculi pterygoidei lateralis

System

Muscle

Region

Head

Side

Paired, left and right

About the inferior head of lateral pterygoid muscle

The lateral pterygoid is a short, thick, two-headed muscle in the infratemporal fossa, deep to the ramus of the mandible and above the medial pterygoid. Its fibres run almost horizontally backwards to the jaw joint, which sets it apart from the other muscles of mastication: temporalis, masseter and medial pterygoid all close the mouth, while the lateral pterygoid helps to open it. The inferior head is the larger of its two heads.

It takes origin from the outer face of the sphenoid's lateral pterygoid plate of the sphenoid bone. From there its fibres converge backwards, upwards and outwards to a small hollow on the front of the neck of the mandible just below the condyle, called the pterygoid fovea. The upper head lies above it, separated by a narrow gap through which the maxillary artery often passes; the buccal nerve, a sensory branch, usually emerges between the two heads.

When the inferior head contracts it pulls the condyle forwards and slightly down out of the mandibular fossa onto the articular eminence. Acting on both sides together, the inferior heads push the lower jaw forwards, in protrusion, and draw the condyles forward as the mouth opens wide, working with the digastric, mylohyoid and geniohyoid, which pull the chin down. When one side acts alone, the chin swings towards the opposite side; alternating action of right and left, together with the medial pterygoids, produces the side-to-side grinding movements of chewing.

Like the other chewing muscles it is supplied by the mandibular division of the trigeminal nerve, through the nerve to lateral pterygoid. Pain, spasm or poor coordination of this muscle is often blamed in temporomandibular disorders, with clicking of the joint, limited opening or deviation of the jaw. A fractured mandibular neck is typically pulled forwards and inwards by the unopposed pull of this head.

Attachments, action and supply

Origin

Outer face of the sphenoid's lateral pterygoid plate.

Insertion

Pterygoid fovea on the front of the neck of the mandible, below the condyle.

Action

Pulls the condyle forwards onto the articular eminence: protrudes and helps depress the mandible; acting on one side, moves the chin to the opposite side.

Nerve supply

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

Blood supply

Pterygoid branches of the maxillary artery.