482.Which of the following is a derivative of the second pharyngeal arch?

A. Eustachian tube
B. External auditory meatus
C. Palatine tonsil
D. Stylohyoid muscle
The correct answer is D. The stylohyoid is derived from the second pharyngeal arch, which also
gives rise to the muscles of facial expression, the stapedius, the posterior belly of the digastric
muscle, Reichert's cartilage, and the facial nerve.

481.During a cranial nerve test, the patient cannot elevate her right eye from the abducted position. Which of the following muscles is paralyzed?

A. Right inferior oblique
B. Right inferior rectus
C. Right lateral rectus
D. Right superior oblique
E. Right superior rectus
The correct answer is E. The superior rectus muscle can elevate and adduct the eye from the
neutral position. From the abducted position, it is the only muscle that can elevate the eye.
The inferior oblique muscle (choice A) can elevate and abduct the eye from the neutral position.
From the adducted position, it is the only muscle that can elevate the eye.
The inferior rectus muscle (choice B) can depress and adduct the eye from the neutral position. From
the abducted position, it is the only muscle that can depress the eye.
The lateral rectus muscle (choice C) can abduct the eye.
The superior oblique muscle (choice D) can depress and abduct the eye from the neutral position.
From the adducted position, it is the only muscle that can depress the eye

480.Hirschsprung's disease indicates a developmental abnormality in which of the following embryonic tissues?

 A. Ectoderm
B. Endoderm
C. Neural crest
D. Neural ectoderm

Ans-c.Neural crest

The baby has Hirschsprung's disease, which is due to an absence of
ganglion cells in the wall of the colon. Neural crest cells contribute to the formation of many adult
structures. Among these are all of the postganglionic neurons of the autonomic nervous system and
the sensory neurons of the peripheral nervous system.