The Lateral Pterygoid Muscle is the only muscle of mastication that protrudes the lower jaw and opens the mouth. With its two-headed structure, it plays a critical role in the movements of the temporomandibular joint (TMJ).

Anatomy

Morphology and Connection Points

The Lateral Pterygoid Muscle is the only muscle with a horizontal course among the muscles of mastication and has two heads. The upper head originates from the infratemporal surface of the sphenoid bone and inserts onto the anterior surface of the joint capsule and disc of the temporomandibular joint (TMJ). The lower head originates from the lateral pterygoid plate of the sphenoid bone and inserts onto the pterygoid fovea at the neck of the mandibular condyle. The upper head functions in joint mechanics, while the lower head functions in most jaw movements. Above the muscle are the temporalis muscle and maxillary artery, while below it is the medial pterygoid muscle. It is also adjacent to branches of the mandibular nerve (CN V₃) and the maxillary artery. The muscle consists of two separate heads: the upper head attaches to the joint capsule and disc, and the lower head attaches to the condyle of the mandible. These different attachments allow the muscle to function in both joint stabilization and mandibular movements. The muscle; It is in close relationship with its neighbors such as the temporal muscle, medial pterygoid muscle and maxillary artery.

Embryological Origin and Classification

The Lateral Pterygoid Muscle originates from the paraxial mesoderm and is part of the first pharyngeal arch muscle group, innervated by the mandibular nerve (CN V₃). Functionally, it is classified as a muscle of mastication and plays a critical role in the movement of the mandible.

Nerve Innervation and Vascular Supply

The neural innervation of this muscle is provided by the lateral pterygoid nerve (n. mandibularis, V3), which arises from the anterior branch of the mandibular nerve and carries motor fibers. This nerve generally provides motor stimulation by sending direct branches to the superior head of the muscle. The vascular supply to the lateral pterygoid muscle is provided by branches arising from the pterygoid segment of the maxillary artery. The pterygoid branches (rr. pterygoidei), in particular, supply blood to both heads of the muscle, meeting its metabolic needs. Additionally, other branches of the maxillary artery, such as the deep temporal arteries and the buccal artery, may contribute. These vessels meet the muscle's oxygen and nutrient needs and are among the anatomical structures that require careful attention during surgical interventions.

Function and Clinical Relationships

The Lateral Pterygoid Muscle plays a key role in the protrusion (forward thrust) and depression (downward pull) movements of the mandible. When contracted bilaterally, it propels the jaw forward, while unilateral contraction shifts the jaw to the opposite side, supporting the grinding action of chewing. It works synergistically with the digastric, mylohyoid, and geniohyoid muscles to open the mandible. It also plays a role in dynamic stabilization of the temporomandibular joint disc. Clinically, overactivity of the lateral pterygoid muscle is a significant pathogenetic factor in TMJ dysfunction. Muscle spasm or anterior displacement of the disc can cause a jaw clicking sound, pain, and limited range of motion. Trismus and other muscle spasms can develop due to infection or trauma. Treatment involves warm compresses and muscle relaxants in mild cases, while botulinum toxin injections may be necessary in severe cases. Care should be taken to avoid traumatizing the muscle during surgical procedures, especially during third molar extraction.