The female Reproductive Cycles
A. The Ovarian Cycle
This term refers to the series of events leading to the release of a mature ovum from the ovary per month per month. It is cyclic event occurring in the ovary of normal females who have attained the age of puberty but not menopause, and are not pregnant. The hormones FSH and LH, influence the cyclic changes that take place in the ovaries.
During each cycle, FSH promotes growth of several primordial follicles into primary follicles; however only one primary follicle usually develops into mature follicle and ruptures through the surface of the ovary, expelling its oocyte. Some experts have asserted that about to 11 follicles degenerate each month.
The events associated with the ovarian cycle are:
1. Development of follicles
2. Ovulation; and
3. Corpus Luteum formation
NB:
Recall that each of these events have been described earlier.
B. The Menstrual Cycle.
The menstrual cycle refers to the period during which the oocyte matures, is ovulated, and enters the uterine tube. Involved in the menstrual cycle include the brain, pituitary gland, uterus and cervix, ovaries, fallopian tubes, and vagina.
Recall that the hormones produced by the ovarian follicles and corpus luteum (estrogen and progesterone) produce cyclic changes in the endometrium. These monthly changes in the internal layer of the uterus (endometrium), constitute the endometrial cycle, commonly referred to as the menstrual cycle or period because menstruation (flow of blood from uterus) is the obvious event.
The average menstrual cycle is 28 days, with day 1 of the cycle designated as the day on which menstrual flow begins.
Menstrual cycles vary in length by several days in normal women. The variations result from the alterations in the durations in the duration of the proliferative phase of the menstrual cycle.
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