AIIMS MCQ for Medical PG Preparations .. NIME | displacement of the artucular disk.. Clinical Case MCQ

In dislocation of the jaw, displacement of the artucular disk beyond the articular tubercle of the temporomandibular joint result from spasm or excessive contraction of which of the following muscles?
A. Buccinators
B. Lateral pterygoid
C. Medial pterygoid
D. Masseter

Ans. B.

The temporalis masseter and medial and lateral pterygoid muscles are the muscles of mastication that attach to the mandible. The buccinator muscle, which controls the contents of the mouth during mastication, is innervated by the seventh cranial nerve and constitutes the chief muscle of facial expression. The lateral pterygoid muscles, acting bilaterally protract the jaw and, acting unilaterally rotate the jaw during chewing. Because the fibers of the superior head of the lateral pterygoid muscle insert onto the anterior aspect of the articular disk of the temporomandibular joint as well as onto the head of the mandible, spasm of this muscle, such as in a yawn, can result in dislocation of the mandible by pulling the disk anterior to the articular tubercle Reduction is accomplished by pushing the mandible downward and back, so that the head of the mandible reenters the mandibular fossa. The temporalis, medial pterygoid and masseter muscles primarily elevate the jaw in molar occlusion.