Endocrine Glands
Answers
223.The answer is b.(Kasper, pp 2127–2129. Junqueira, pp 400–402, 406.)
Metabolism in the adrenal medulla is regulated by glucocorticoids because
they induce the enzyme phenylethanolamine-N-methyltransferase, which
catalyzes the methylation of norepinephrine to epinephrine. Most of the
blood supply entering the medulla passes through the cortex. Glucocorti-
coids synthesized in the zona fasciculata of the adrenal are released into the
sinusoids and enter the medulla (answers a and e).The adrenal gland is not
usually considered a classic portal system although there are similarities.
Monoamine oxidase is a mitochondrial enzyme that regulates the storage of
catecholamines in peripheral sympathetic nerve endings (answers c and d).
The adrenal gland functions as two separate glands. The adrenal cortex is
derived from mesoderm and the adrenal medulla from neural crest. The
blood supply to the adrenal is derived from three adrenal arteries: (1) the
superior adrenal (suprarenal) from the inferior phrenic, (2) the middle
adrenal from the aorta, and (3) the inferior adrenal from the renal artery.
224.The answer is e.(Kasper, pp 234, 2136, 2148. Junqueira, p 407. Kumar,
pp 1219–1221.)Patients with a pheochromocytoma often have paroxysms
that are the hallmark of this tumor. These are seizure-like catecholamine-
induced attacks that include headache, profuse sweating, palpitations, and
overall anxiety. Pheochromocytoma is a common tumor of the adrenal
medulla that leads to an excess of norepinephrine, which causes hyperten-
sion and hyperglycemia. Vasoconstriction of arterioles occurs in conjunc-
tion with the increased blood pressure. Epinephrine (e.g., cortisol and
growth hormone) have anti-insulin effects, thus causing hyperglycemia.
225.The answer is b.(Junqueira, p 417. Kumar, pp 1223–1224.)The pho-
tomicrograph and the MRI illustrate the structure of the pineal gland, or epi-
physis cerebri, which arises as an outgrowth of the diencephalon (answer a).
The pinealocytes secrete melatonin in response to the light-dark cycle and
influence the rhythmicity of other endocrine organs. In a sense, the pineal,
therefore, functions as a biologic clock. The pineal contains two main cell
types: pinealocytes and neuroglia [the latter appear to be modified astrocytes
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