16 Facts About The Menstrual Cycle
Menstruation is the periodic discharge of blood, mucus, and epithelial cells from the uterus. It usually occurs at monthly intervals throughout the reproductive period, except during pregnancy and lactation, when it is usually suppressed.
a. The menstrual cycle is controlled by the cyclic activity of follicle stimulating hormone (FSH) and LH from the anterior pituitary and progesterone and estrogen from 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).
hypothalamus
Functional Layer
Pituitary Gland
Anterior
Follicle-stimulating Hormonev
FOLLICULAR PHASE
Pituitary Gland
Anterior
Posterior
Luteinizing Hormone (LH).
Primary Follicle
Menstruation
Follicle-stimulating Hormonev
FOLLICULAR PHASE
Graafian Follicle
J OVULATION
Estrogen I
Proliferative Phase T
Posterior
Luteinizing Hormone (LH).
Corpus Luteum I
Progesterone
Some Estrogen ♦
Secretory Phase
Degenerating Corpus Luteum
Hypothalamic-pituitary
Cycle
_ Pituitary
Hormones
Corpus Luteum I
Progesterone
Some Estrogen ♦
Secretory Phase
Degenerating Corpus Luteum
Ischemic Phase Menstruation
Ovarian Cycle
Ovarian Hormones
Functional Layer
Menstruation
Graafian Follicle
J OVULATION
Estrogen I
Proliferative Phase T
Ischemic Phase Menstruation
Endometrial Cycle
10 14
Figure 1-7. Menstrual cycle.
Endometrial Cycle
10 14
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 glands secrete nutrients into the uterine cavity, helping to prepare the lining for the arrival of the fertilized egg. If the egg is fertilized, the embryo produces human chorionic gonadotropin (HCG). Thehuman chorionic gonadotropin signals the corpus luteum to continue to supply progesterone to maintain the uterine lining. Continuous levels of progesterone prevent the release of FSH and ovulation ceases.
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