Figure 48-1. The ovarian cycle.
(Reproduced, with permission, from Devlin
TM, ed.
Textbook of Biochemistry with Clinical Correlations,
5th ed. New
York: Wiley-Liss, Copyright © 2002:935. This material is used by permission
of John Wiley & Sons, Inc.)
and estradiol, culminating with apoptosis of the uterine endometrial cells, and
their shedding at day 28 in menstruation. A new follicle then begins to
develop. The decline in blood levels of estradiol and progesterone relieves
feedback inhibition of the gonadotropes and hypothalamus, leading to GnRH
release and initiation of another ovarian cycle.
If fertilization occurs, the corpus luteum remains viable and begins secre-
tion of human chorionic gonadotropin (HCG), a function eventually taken over
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