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CHAPTER 14 Women’s Health
average age of menarche for African-Americans is 9 to 11 years while for Cau-
casians it is from 10 to 12 years. The cycle is controlled by hormones from the hypo-
thalamus, pituitary, ovaries, and the uterus. A normal menstrual cycle is 28 days,
but only about 25 percent of women actually are on this schedule. The average can
run from 21 to 35 days. The menstrual cycle is often divided into three phases,
dependent upon the hormones. The beginning of menstruation is the start of the
follicular phase which lasts until day 14. As hormone levels are low, the thickened
lining of the uterus begins to shed. The cramping that is felt is from small uterine
contractions, helping to shed the lining. An egg follicle begins to mature due to
growing levels of follicle-stimulating hormone (FSH), which also causes estrogen
secretion. The increase in estrogen causes the endometrium to mature and thicken.
The last five days of the follicular phase plus the day of ovulation are the most fer-
tile days. Upon ovulation, on day 14, the oocyte, or egg, is released from the follicle
due to a surge in luteinizing hormon (LH). The egg is expelled near the opening of
one of the fallopian tubes, (oviducts, uterine tubes), located laterally at the top of the
uterus. Fertilization usually occurs in one of the tubes. The embryo now travels to
the uterus, the primary job of which is to sustain development. A nonpregnant uterus
measures about 7 × 5 cm. As it is a muscular organ, it is capable of great stretching.
At the distal end of the uterus is the cervix which attaches to the superior portion of
the vagina. The luteal phase starts next with LH causing the follicle to secrete prog-
esterone instead of estrogen. Progesterone causes the endometrial lining to begin to
thicken in preparation for implantation of a fertilized cell. Progesterone inhibits
release of FSH and LH. If fertilization does not occur, the corpus luteum, containing
the oocyte, dies, which lowers the level of progesterone. Sloughing of the lining
begins about the 28th day of the cycle, resulting in a flow of blood and cellular debris
through the vagina. The cycle will begin again. Primary amenorrhea is the absence
of menses by age 16. Secondary amenorrhea is the absence of menses for more than
6 months in a woman who previously was menstruating regularly.
Just the Facts
Breast Cancer
Studies show that by age 80, about 1 in 8 women will have breast cancer. Ten per-
cent of all breast cancers are inherited. Two major genes have been identified—
BRCA1 and BRCA2.
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