Secondary Sex Characteristics

Chemo Secrets From a Breast Cancer Survivor

Breast Cancer Survivors

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The secondary sex characteristics of the female, like those of the male, are features other than the genitalia that develop at puberty, serve to distinguish the sexes from each other, and serve the purpose of sexual attraction. These include the distribution of body fat, flare of the pelvis, the breasts, and the resulting feminine physique; the relatively fine body hair; and a voice pitched higher than the male's.

The Breasts

The breast (fig. 28.9) is a mound of tissue overlying the pectoralis major. It has two principal regions: the conical to pendulous body, with the nipple at its apex, and an extension toward the armpit called the axillary tail. Lymphatics of the axillary tail are especially important as a route of breast cancer metastasis.

The nipple is surrounded by a circular colored zone, the areola. Dermal blood capillaries and nerves come closer to the surface here than in the surrounding skin and make the areola more sensitive and more reddish in color. In pregnancy, the areola and nipple often darken and become more visible to the indistinct vision of a nursing infant. Sensory nerve fibers of the areola are important in triggering a milk ejection reflex when an infant nurses. The areola has sparse hairs and areolar glands, visible as small bumps on the surface. These glands are intermediate between sweat glands and mammary glands in their degree of development. When a woman is nursing, the areola is protected from chapping and cracking by secretions of the areolar glands and sebacous glands of the areola. The dermis of the areola has smooth muscle fibers that contract in response to cold, touch, and sexual arousal, wrinkling the skin and erecting the nipple.

Internally, the nonlactating breast consists mostly of adipose and collagenous tissue (fig. 28.10). Breast size is determined by the amount of adipose tissue and has no relationship to the amount of milk the mammary gland can produce. Suspensory ligaments attach the breast to the dermis of the overlying skin and to the fascia of the pectoralis major. The nonlactating breast contains very little glandular tissue, but it does have a system of ducts branching through its connective tissue stroma and converging on the nipple. When the mammary gland develops during pregnancy, it exhibits 15 to 20 lobes arranged radially around the nipple, separated from each other by fibrous stroma. Each lobe is drained by a lactiferous23 duct, which dilates to form a lactiferous sinus opening onto the nipple. Lactation and the associated changes in breast structure are described at the end of this chapter.

Adipose tissue

Intercostal muscles

Pectoralis minor muscle-(

Pectoralis major muscle

Deep fascia -

Adipose tissue

Intercostal muscles

Deep fascia -

Coloured Photographs Breast Structure
Figure 28.9 Anatomy of the Lactating Breast. (a) Sagittal section of breast. (b) Surface anatomy of the breast with cutaway view of the lobes of mammary gland; anterior view of left breast.

Saladin: Anatomy & I 28. The Female I Text I I © The McGraw-Hill

Physiology: The Unity of Reproductive System Companies, 2003 Form and Function, Third Edition

1058 Part Five Reproduction and Development

1058 Part Five Reproduction and Development

Mammary Gland Dissection

Adipose tissue Pectoralis major muscle

Suspensory ligaments

Fibrous tissue Skin

Lactiferous sinuses Nipple

Superficial fascia

Figure 28.10 Sagittal Section of the Breast of a Cadaver.

Adipose tissue Pectoralis major muscle

Suspensory ligaments

Fibrous tissue Skin

Lactiferous sinuses Nipple

Superficial fascia

Figure 28.10 Sagittal Section of the Breast of a Cadaver.

Treatment of breast cancer is usually by lumpectomy (removal of the tumor only) or simple mastectomy (removal of the breast tissue only or breast tissue and some axillary lymph nodes). Radical mastectomy, rarely done since the 1970s, involves the removal of not only the breast but also the underlying muscle, fascia, and lymph nodes. Although very disfiguring, it proved to be no more effective than simple mastectomy or lumpectomy. Surgery is generally followed by radiation or chemotherapy, and estrogen-sensitive tumors may also be treated with an estrogen blocker such as tamoxifen. A natural-looking breast can often be reconstructed from skin, fat, and muscle from other parts of the body.

Before You Go On

Answer the following questions to test your understanding of the preceding section:

1. How do the site of female gamete production and mode of release from the gonad differ from those in the male?

2. How is the structure of the uterine tube mucosa related to its function?

3. Contrast the function of the endometrium with that of the myometrium.

4. Describe the similarities and differences between the clitoris and penis.

Breast Cancer

Breast cancer (fig. 28.11) occurs in one out of every eight or nine American women and is one of the leading causes of female mortality. Breast tumors begin with cells of the mammary ducts and may metastasize to other organs by way of the mammary and axillary lymphatics. Symptoms of breast cancer include a palpable lump (the tumor), puckering of the skin, changes in skin texture, and drainage from the nipple.

Two breast cancer genes were discovered in the 1990s, named BRCA1 and BRCA2, but most breast cancer is nonhereditary. Some breast tumors are stimulated by estrogen. Consequently, breast cancer is more common among women who begin menstruating early in life and who reach menopause relatively late—that is, women who have a long period of fertility and estrogen exposure. Other risk factors include aging, exposure to ionizing radiation and carcinogenic chemicals, excessive alcohol and fat intake, and smoking. Over 70% of cases, however, lack any identifiable risk factors.

The majority of tumors are discovered during breast self-examination (BSE), which should be a monthly routine for all women. Mammograms (breast X rays), however, can detect tumors too small to be noticed by BSE. Although opinions vary, a schedule commonly recommended is to have a baseline mammogram in the late 30s and then have one every 2 years from ages 40 to 49 and every year beginning at age 50.

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Essentials of Human Physiology

Essentials of Human Physiology

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