CorpusHuman Anatomy
MuscularMuscle

Lateral pterygoid

Musculus pterygoideus lateralis

Also known as: external pterygoid

A short, two-headed muscle running horizontally from the sphenoid to the neck of the mandible and the TMJ disc. It is the only muscle of mastication that opens (depresses and protrudes) the jaw.

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Overview

Lateral pterygoid has a superior head, from the infratemporal surface and crest of the greater wing of the sphenoid, and an inferior head, from the lateral surface of the lateral pterygoid plate. The fibres run backward almost horizontally. They insert into the pterygoid fovea on the neck of the mandible and into the capsule and articular disc of the temporomandibular joint.

Wide opening of the mouth needs the condyle and disc to glide forward onto the articular eminence, and lateral pterygoid produces that glide. The inferior head pulls the condyle forward to start depression and protrusion, helped by gravity and the suprahyoid muscles. The superior head is active mainly during closure, when it steadies the disc and condyle. When one side contracts with its medial pterygoid, the chin swings to the opposite side.

With a lesion of V3, the jaw deviates toward the paralysed side on opening, because the healthy lateral pterygoid pushes the chin across.

Location

Roof of the infratemporal fossa, between the sphenoid and the condyle of the mandible.

Parts & subdivisions

  1. Superior head
    From the greater wing of the sphenoid to the TMJ capsule and disc. Stabilises the disc during closure.
  2. Inferior head
    From the lateral pterygoid plate to the pterygoid fovea. Protrudes and depresses the mandible.

Anatomy

Origin

Superior head: infratemporal surface and infratemporal crest of the greater wing of the sphenoid. Inferior head: lateral surface of the lateral pterygoid plate.

Insertion

Pterygoid fovea on the neck of the mandible; capsule and articular disc of the TMJ.

Action

Bilaterally: protrudes the mandible and depresses the chin (opening). Unilaterally: moves the chin to the opposite side.

Innervation

Nerve to lateral pterygoid (anterior division of the mandibular nerve, CN V3).

Nerve roots

Cranial nerve V3; no spinal roots

Arterial supply

Pterygoid branches of the maxillary artery (the maxillary artery passes superficial or deep to the muscle).

Relations

The maxillary artery runs over or under it. The pterygoid venous plexus surrounds it. The buccal nerve emerges between its two heads.

Function

  • Opens the mouth by protruding the condyle and disc
  • Protrudes the mandible (bilaterally)
  • Side-to-side grinding (unilaterally, toward the opposite side)

Clinical significance

Jaw deviation in V3 lesions

Paralysis of one lateral pterygoid causes the mandible to deviate toward the side of the lesion on opening.

TMJ dislocation

Excessive contraction during a yawn can pull the condyle anterior to the articular eminence, so the jaw locks open. It is reduced by pressing down on the molars and pushing backward.

Test yourself

Which muscle of mastication opens (depresses and protrudes) the jaw?
  1. Masseter
  2. Temporalis
  3. Medial pterygoid
  4. Lateral pterygoid

Answer: Lateral pterygoid

The lateral pterygoid pulls the condyle and articular disc forward onto the articular eminence. The other three muscles elevate the mandible. With a V3 lesion, the jaw deviates toward the paralysed side on opening.

More muscular system questions

Compiled from standard anatomy and physiology references — see the Muscular System sources. For education only; not medical advice.