Location and anatomy
- Origin (O): originates from the roof of the infratemporal fossa (fossa infratemporalis) and the lateral plate of the pterygoid process.
- Insertion (I): fibers run towards the neck of the condylar process of the mandible, and also blend directly into the capsule and articular disc of the temporomandibular joint (TMJ).
Anatomically, the muscle is divided into two portions — the superior and inferior heads, which have significant differences in biomechanics.
How the muscle works (function and biomechanics)?
The lateral pterygoid muscle belongs to the group of muscles of mastication, but its primary task is not elevation, but rather the displacement of the jaw in various planes:
- Protrusion: the muscle pulls the mandible forward. In this process, the articular heads along with the discs shift downward and forward along the slopes of the articular tubercles (forming the sagittal articular pathway with a Gysi angle averaging 33°).
- Laterotrusion (lateral occlusions): during unilateral contraction, the jaw shifts to the side opposite to the contracting muscle. On the balancing side, the jaw head shifts downward, forward, and medially, while on the working side, it rotates around its own axis.
- Reciprocal action of the heads: the superior and inferior heads function reciprocally. The superior head is responsible for the position of the articular disc. When the jaw head shifts backward, it performs an elongating contraction (it does not shorten, but slows down its stretch), returning the disc to its initial position. The muscle tone largely depends on the occlusion of the dental arches.
Topography and adjacent structures
The muscle is a key landmark of the deep facial region and participates in the formation of important fascial spaces:
- Interpterygoid space (spatium interpterygoideum): located between the lateral and medial pterygoid muscles. Branches of the mandibular nerve, enclosed in the interpterygoid fascia, pass here.
- Pterygomandibular space: the lateral pterygoid muscle serves as its upper boundary. Inflammatory processes (abscesses and phlegmons) in this zone arise from an infection originating from the lower molars or as a complication of mandibular anesthesia, causing inflammatory contracture — a marked limitation in mouth opening.
- Relationship to nerves: the buccal nerve (n. buccalis) emerges outward directly between the two heads of the lateral pterygoid muscle. Deep temporal nerves wrap around the muscle superiorly, and the inferior alveolar nerve (n. alveolaris inferior) runs beneath it. Surgical access to the deep branches of the trigeminal nerve requires dissection of this muscle.
Blood supply and innervation
- Blood supply: provided by pterygoid branches (rr. pterygoidei) from the second (pterygoid) part of the maxillary artery (a. maxillaris). The maxillary artery itself — one of the most complex vessels of the head — wraps around the neck of the articular process and runs transversely across the outer surface of the lateral pterygoid muscle or between it and the temporalis muscle. Additionally, the buccal artery (a. buccalis) may be located on the outer surface of the muscle.
- Innervation: supplied by the motor branches of the third branch of the trigeminal nerve (V3) — the mandibular nerve (n. mandibularis). The trunk of this nerve is short (up to 0.5 cm), and its branches run within the interpterygoid space.
Class and exam questions
In which direction does the jaw shift during contraction of the left lateral pterygoid muscle?
During unilateral contraction of the lateral pterygoid muscle, the mandible shifts to the opposite side. Consequently, when the left muscle contracts, the jaw shifts to the right.
Which muscle blends directly into the capsule and disc of the TMJ?
Lateral pterygoid muscle. Its fibers attach to the capsule and articular disc, allowing the superior head of the muscle to control the position of the disc during jaw movements.
Where does the buccal nerve run in relation to the lateral pterygoid muscle?
The buccal nerve (n. buccalis) passes directly between the superior and inferior heads of the lateral pterygoid muscle, running downward and forward toward the lateral wall of the oral cavity.
What else to study on this topic
- Temporomandibular joint (TMJ)
- Maxillary artery (a. maxillaris)
- Mandibular nerve (n. mandibularis)
- Pterygomandibular fascial space
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