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.