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Figure

(a) Light micrograph of a mammary gland in a nonpregnant woman (60x micrograph enlarged to 160x). (fa) Light micrograph of an active (lactating) mammary gland (60x micrograph enlarged to 160x).

Duct

Secretion

Secretion

Duct

(Lumen)

Myoepithelial cell

Figure 22.43

Myoepithelial cells eject milk from an alveolar gland.

(Lumen)

Myoepithelial cell

Figure 22.43

Myoepithelial cells eject milk from an alveolar gland.

Nipple or areola of breast Is mechanically stimulated

Nerve impulses travel to hypothalamus

Nerve impulses travel to hypothalamus

Milk is ejected from ductile system through nipple

Figure 22.44

Mechanism that ejects milk from the breasts.

Milk is ejected from ductile system through nipple

Figure 22.44

Mechanism that ejects milk from the breasts.

A woman who is breast-feeding feels her milk "let down," or flood her breasts, when her infant suckles. If the baby nurses on a very regular schedule, the mother may feel the letdown shortly before the baby is due to nurse. The connection between mind and hormonal control of lactation is so strong that if a nursing mother simply hears a baby cry, her milk may flow. If this occurs in public, she can keep from wetting her shirt by pressing her arms strongly against her chest.

To wean a nursing child, it is best to stop breastfeeding gradually, by eliminating one feeding per day each week, for example. If a woman stops nursing abruptly, her breasts will become painfully engorged for several days.

A woman who is breast-feeding usually does not ovulate for several months. This may be because pro-lactin suppresses release of gonadotropins from the anterior pituitary gland. When a woman discontinues breast-feeding, the anterior pituitary no longer secretes prolactin. Then, FSH is released, and the menstrual cycle is activated. If a new mother does not wish to repeat her recent childbirth experience soon, she or her partner should be practicing contraception, because she will be fertile during the two weeks prior to the return of her menstrual period.

Table 22.7 summarizes the hormonal control of milk production, and table 22.8 lists some agents that adversely affect lactation or harm the child. Clinical Application 22.6 explains the benefits of breast-feeding.

99 Describe the structure of a mammary gland.

^9 How does pregnancy affect the mammary glands?

^9 What stimulates the mammary glands to produce milk?

□ What causes milk to flow into the ductile system of a mammary gland?

Q What happens to milk production if milk is not regularly removed from the breast?

Birth Control

Birth control is the voluntary regulation of the number of offspring produced and the time they will be conceived. This control requires a method of contraception (kon"trah-sep'shun) designed to avoid fertilization of an egg cell following sexual intercourse or to prevent implantation of a very early developing embryo. Table 22.9 describes several contraceptive approaches and devices and indicates their effectiveness.

Coitus Interruptus

Coitus interruptus is the practice of withdrawing the penis from the vagina before ejaculation, preventing entry of sperm cells into the female reproductive tract. This method of contraception often proves unsatisfactory and may result in pregnancy, since a male may find it difficult to withdraw just prior to ejaculation. Also, some semen containing sperm cells may reach the vagina before ejaculation occurs.

Rhythm Method

The rhythm method (also called timed coitus or natural family planning) requires abstinence from sexual intercourse a few days before and a few days after ovulation. The rhythm method results in a relatively high rate of

Treating Breast Cancer

One in eight women will develop breast cancer at some point in her life (table 22E). Breast cancer is really several illnesses. As information on the human genome reveals the cellular and molecular characteristics that distinguish subtypes of the disease, treatments old and new are being increasingly tailored to individuals, at the time of diagnosis. This "rational" approach may delay progression of disease and increase survival rate for many women and enable them to avoid drug treatments that will not work.

^Varning Signs

Changes that could signal breast cancer include a small area of thickened tissue, a dimple, a change in contour, or a flattened nipple or one that points in an unusual direction or produces a discharge. A woman can note these changes by performing a monthly "breast self exam," in which she lies flat on her back with the arm raised behind her head and systematically feels all parts of each breast. But sometimes breast cancer gives no warning at all—early signs of fatigue and feeling ill may not occur until the disease has spread beyond the breast.

If a woman finds a lump in a breast, the next step is a physical exam, where a health care provider palpates the breast and does a mam-mogram, which is an X-ray scan that can pinpoint the location and approximate extent of abnormal tissue (fig. 22E). An ultrasound scan can distinguish between a cyst (a fluid-filled sac of glandular tissue) and a tumor (a solid mass). If an area is suspicious, a thin needle is used to take a biopsy (sample) of the tissue, whose cells will be scrutinized for the telltale characteristics of cancer.

Eighty percent of the time, a breast lump is a sign of fibrocystic breast disease, which is benign (non-cancerous). The lump may be a cyst or a solid, fibrous mass of connective tissue called a fibroadenoma. Treatment for fibrocystic breast disease includes taking vitamin E or synthetic androgens under a doctor's care, lowering caffeine intake, and examining unusual lumps further.

Surgery, Radiation, and chemotherapies

If biopsied breast cells are cancerous, treatment usually begins with surgery. A

lumpectomy removes a small tumor and some surrounding tissue; a simple mastectomy removes a breast; and a modified radical mastectomy removes the breast and surrounding lymph nodes, but preserves the pectoral muscles. Radical mastectomies, which remove the muscles too, are rarely done anymore. In addition, a few lymph nodes are typically examined, which allows a physician to identify the ones that are affected and must be removed.

Most breast cancers are then treated with radiation and combinations of chemotherapeutic drugs, plus sometimes newer drugs that are targeted to certain types of breast cancer. Standard chemotherapies kill all rapidly-dividing cells, and those used for breast cancer include fluo-rouracil, doxorubicin, cyclophos-phamide, and methotrexate. A newer chemotherapeutic agent is paclitaxol, which was originally derived from the bark of yew trees. Drugs related to taxol but that are less toxic are also used. Many times physicians can

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