Medial pterygoid

Musculus pterygoideus medialis

Also known as: internal pterygoid

A thick quadrilateral muscle on the inner side of the ramus that mirrors masseter. It elevates and protrudes the mandible and produces side-to-side grinding movements.

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Overview

Medial pterygoid has a large deep head, arising from the medial surface of the lateral pterygoid plate and the pyramidal process of the palatine bone, and a small superficial head, arising from the maxillary tuberosity and pyramidal process. The superficial head wraps around the lower head of lateral pterygoid. The fibres run downward, backward and laterally to the medial surface of the ramus and angle of the mandible. There it forms, with masseter, the pterygomasseteric sling.

It works with masseter and temporalis to close the jaw and with lateral pterygoid to protrude it. When the medial and lateral pterygoids of one side act together, they swing the chin to the opposite side. Alternating this on both sides produces the grinding (lateral) movements of chewing. The lingual and inferior alveolar nerves descend between it and the ramus (the pterygomandibular space), where an inferior alveolar nerve block is given.

Location: Infratemporal fossa, on the medial side of the ramus of the mandible.

Parts & subdivisions

Deep head
From the medial surface of the lateral pterygoid plate.
Superficial head
From the maxillary tuberosity and the pyramidal process of the palatine bone.

Anatomy

Origin: Deep head: medial surface of the lateral pterygoid plate and the pyramidal process of the palatine bone. Superficial head: maxillary tuberosity and pyramidal process.
Insertion: Medial surface of the ramus and angle of the mandible, below the mandibular foramen.
Action: Elevates and protrudes the mandible. Unilateral contraction moves the chin to the opposite side.
Innervation: Nerve to medial pterygoid (main trunk of the mandibular nerve, CN V3).
Nerve roots: Cranial nerve V3; no spinal roots
Arterial supply: Pterygoid branches of the maxillary artery.
Relations: The lingual and inferior alveolar nerves and the inferior alveolar vessels pass between it and the ramus (the pterygomandibular space).

Function

Elevates the mandible
Protrudes the mandible (bilaterally)
Grinding: moves the chin to the opposite side (unilaterally)

Clinical significance

Inferior alveolar nerve block

The needle enters the pterygomandibular space lateral to medial pterygoid. Injecting into the muscle causes post-injection trismus.

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