palatopharyngeal arch, likewise is formed by the palatopharyngeus muscle.
The palatoglossus and palatopharyngeus muscles insert into the tongue and
pharynx, respectively, and both are innervated by the pharyngeal branch of
the vagus nerve (CN X). The salpingopharyngeus muscle (answer c),also
innervated by the pharyngeal branch of the vagus nerve, arises from the torus
tubarius at the opening of the auditory tube and inserts into the pharyngeal
musculature. The superior and middle pharyngeal constrictors (answer e)
are innervated by the pharyngeal branch of the vagus nerve. The stylopha-
ryngeus and styloglossus muscles (answer d)originate from the styloid
process and insert onto the lesser horn of the hyoid and into the tongue,
respectively. They are innervated by the glossopharyngeal and hypoglossal
nerves, respectively. Levator veli palatini and tensor veli palatini muscles
(answer a)are above the soft palate.
301.The answer is d.(Sadler, pp 285–291.)After closure of the neural
tube, cells proliferate and establish three primitive layers: (1) the ventric-
ular zone adjoining the central canal and ventricles; mitoses of neuronal
and glial precursors continue in this zone; (2) a mantle zone consisting of
cell bodies of neurons and glia that have migrated out of the ventricular
zone; and (3) a marginal zone on the periphery containing the myelinated
nerve processes characteristic of white matter. Closure of the neural tube
begins near the midpoint of its length and proceeds in both directions
simultaneously (thus not answers a and c). The neurectoderm of the
neural tube will give rise to neurons and some glial cells (astrocytes, oligo-
dendroglia, and ependymal cells), but the precursors of microglia (the
monocyte-macrophage lineage) migrate into the nervous system from the
blood (thus not answer b). The sensory ganglia are formed by neural crest
cells that migrated before the development of mature neurons (answer e).
302.The answer is a.(Moore and Dalley, pp 930–931.)The most likely
diagnosis is a subarachnoid hemorrhagic stroke, which had stopped by the
time the CT, was performed. While most strokes present with sudden onset
of neurological symptoms, the majority of stokes are ischemic (answer b)in
nature due to blood clots blocking blood to the brain. In this man, however,
he probably had a hemorrhagic stroke as a consequence of increased blood
pressure due to straining, because of constipation. This is also consistent
with his developing headache, stiff neck and blood within the CSF collected
446 Anatomy, Histology, and Cell Biology