293.The answer is a. (Waxman, pp 86–91, 117–122.) The nucleus
ambiguus, along with special visceral efferent (SVE) components of CN IX,
X, and XI, is a column of lower motor neurons that innervate muscles of the
pharynx, larynx, and palate. Damage to this nucleus results in loss of the gag
reflex, difficulty in swallowing, and hoarseness. The lateral spinothalamic
tract(answer b)passes through the medulla and carries sensory information
(pain and temperature) from the contralateral extremities and trunk. Simi-
larly, the spinal tract of CN V (answer c)carries pain and temperature sensa-
tion from the ipsilateral face. Descending sympathetic pathways (answer d)
course through the medulla to reach the intermediolateral cell column of the
spinal gray matter. Damage to those fibers would result in loss of ability to
dilate the pupil (meiosis), drooping eyelid (ptosis), and loss of sweating ipsi-
laterally (hemianhydrosis). Damage to nerve fibers passing to and from the
cerebellum via the inferior cerebellar peduncle (answer e)would result in
intention tremor and lack of coordination.
294.The answer is b.(Moore and Dalley, pp 986–987.)The temporalis, mas-
seter, and medial and lateral pterygoid muscles are the muscles of mastication
that attach to the mandible. The buccinator muscle (answer a),which controls
the contents of the mouth during mastication, is innervated by the facial CN
VII. The lateral pterygoid muscles, acting bilaterally, protract the jaw and, act-
ing unilaterally, rotate the jaw during chewing. Because the fibers of the supe-
rior 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 (answer e),
medial pterygoid (answer c),and masseter (answer d)muscles primarily ele-
vate the jaw in molar occlusion.
295.The answer is c.(Moore and Dalley, p 1111.)This congenital anom-
aly is a branchial fistula. When the pharyngeal pouches persist, they may
form connections to the exterior of the neck immediately anterior to the
boundary of the sternocleidomastoid muscle. Since this weeps fluid it is
most likely a fistula or external cyst (which was not one of the options).
An internal branchial sinus (answer b)would only be a blind pouch off
Head and Neck Answers 443