0071509674.pdf

232.The answer is c.(Young, pp 309–314. Moore and Persaud, Developing,
pp 445–448. Junqueira, pp 392–399. Sadler, pp 300–301.)The region of the
pituitary labeled C is the pars distalis, which contains corticotrophs, thy-
rotrophs, lactotrophs, and gonadotrophs that synthesize trophic hormones
which regulate other endocrine organs. The anterior pituitary is unique in that
it depends on the presence of the hypothalamo-hypophyseal portal system.
Releasing and inhibitory factors are transported from the cell bodies in the
hypothalamus along axons into the median eminence, where the secretion is
released into a primary capillary plexus. The hypothalamo-hypophyseal por-
tal system carries blood from the primary plexus to the secondary plexus,
which comprises the sinusoids of the pars distalis. This system brings the
hypothalamic hormones into close proximity with the appropriate cell types
in the pars distalis. For example, CTH-RF (corticotropin-releasing factor,
CRH) is synthesized in the hypothalamus, released into the primary capil-
lary plexus in the median eminence, and subsequently carried in the por-
tal system to the secondary capillary plexus, where it interacts with
corticotrophs in the pars distalis. The pars nervosa is the neurally con-
nected portion of the pituitary and contains the dilated axons of hypothal-
amic cell bodies that produce vasopressin and oxytocin.

356 Anatomy, Histology, and Cell Biology

Zona Mineralocorticoids Collecting Angiotensin II

glomerulosa (aldosterone) tubules

Zona Glucocorticoids Gluconeogenesis ACTH (adrenocortico-

fasciculata (cortisol, hydro- by the liver tropic hormone)

cortisone) and

weak androgens

Zona Glucocorticoids Androgens are ACTH

reticularis and weak precursors of

androgens estradiol in the

fetus

Medulla Norepinephrine Preparation for Preganglionic

and epinephrine “flight or fight” sympathetic fibers

from the splanchnic

nerves

Regulatory

Zone Secretion Target Factors

The adrenal hormones are listed in the table below.