Reproductive Systems
Answers
235.The answer is d.(Junqueira, pp 427–428. Guyton, pp 930–933.
Kierszenbaum, pp 571–573.)Estrogen levels increase during the maturation of
ovarian follicles, which results in a concomitant increase in ciliation and
height of the oviductal lining cells. Increases in the number of cilia serve to
facilitate movement of the ovum. Increased estrogen levels also decrease FSH
levels and cause an LH surge (answers a and c).Elevated estrogen levels
result in increased secretion of lytic enzymes, prostaglandins, plasminogen
activator, and collagenase to facilitate the rupture of the ovarian wall and the
release of the ovum and the attached corona radiata. Following ovulation,
during the luteal phase of the cycle, the theca and granulosa cells are trans-
formed into the corpus luteum under the influence of LH. Ovulation occurs
near the middle of the menstrual cycle and is associated with an increase in
basal body temperature that appears to be indirectly regulated by elevated
estrogen levels, with IL-1 functioning as the endogenous pyrogen. Estrogen
also upregulates FSH receptors on granulosa cell membranes and enhances syn-
thesis and storage of glycogen in the vaginal epithelium (answers b and e).
236.The answers is c.(Young, pp 329–331. Junqueira, pp 420, 427.)The
cell marked with a star is a Leydig cell (i.e., interstitial cell) and is regulated
by luteinizing hormone (LH), formerly known as interstitial cell–stimulating
hormone (ICSH), secreted by gonadotrophs in the anterior pituitary. Leydig
cells are located between seminiferous tubules and are responsible for the
production of testosterone. The star delineates a cluster of Leydig cells,
found between the seminiferous tubules. The Leydig cells normally synthe-
size and release testosterone in response to LH that is produced by
gonadotrophs in the anterior pituitary. Leydig cell tumors develop in males
between 20 and 60 years of age and produce androgens, estrogens, and
sometimes glucocorticoids. Calcitonin is synthesized by C cells in the thy-
roid (answer a).Progesterone (answer b)is synthesized by corpora lutea
under the influence of LH. FSH (follicle- stimulating hormone) plays a key
physiological role in both males (spermatogenesis) and females (regulation
of follicular growth) and is produced and released by gonadotrophs in the
anterior pituitary (answer d).FSH stimulates the maturation of ovarian
373