the ovaries. In other words, FSH acts upon the ovary to stimulate the maturation of a
follicle, and during this development, the follicular cells secrete increasing amounts of
estrogen (see figure 1-7).
Figure 1-7. Menstrual cycle.
b. Hormonal interaction of the female cycle are as follows:
(1) Days 1-5. This is known as the menses phase. A lack of signal from a
fertilized egg influences the drop in estrogen and progesterone production. A drop in
progesterone results in the sloughing off of the thick endometrial lining which is the
menstrual flow. This occurs for 3 to 5 days.
(2) Days 6-14. This is known as the proliferative phase. A drop in
progesterone and estrogen stimulates the release of FSH from the anterior pituitary.
FSH stimulates the maturation of an ovum with graafian follicle. Near the end of this
phase, the release of LH increases causing a sudden burst like release of the ovum,
which is known as ovulation.
(3) Days 15-28. This is known as the secretory phase. High levels of LH
cause the empty graafian follicle to develop into the corpus luteum. The corpus luteum
releases progesterone, which increases the endometrial blood supply. Endometrial