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
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.
