Although both men and women have breasts, it is in the female that the breast becomes prominent and is a vital component of' her persona (Fig 2.1). In the male, the breast is rudimentary.

The female breast is a symbol of womanhood and femininity. But at the same time it has an important function.

It is an organ that under appropriate stimulation will produce milk. This breast milk comes from tiny glands within the breast that: resemble bunches of grapes. Breast milk is essential for the sustenance and growth of the newborn baby.

The breast is in fact a modified sweat gland. But while the sweat gland secretes “...... sweat (perspiration), the mammary gland secretes milk.

Structure

The anatomy of the breast is quite simple.

It is made up of about eighteen lobules of glandular tissue. These lobules resemble bunches of grapes (Fig 2.2) and each grape represents the secreting unit, called alveolus (pleural: alveoli).
The alveolus consists of cells, which line the unit (Fig 2.3) and produce the milk.

Blood supply to the breast

The main blood supply comes from the internal mammary artery, which comes off the subclavian artery, which supplies the arm. This is one of the main branches of the arch of the aorta. Additional supplies come from branches of the axillary artery and from the intercostal arteries of the pectoralis major muscle overlying the breast. The venous drainage corresponds with the arterial supply.

Function

The physiology of the breast is directly dependent on parts of the body's endocrine system. This system is essential in controlling the function of the human body. This is done by the production of hormones by these endocrine glands. These hormones are chemical messengers that circulate in the blood stream and act on organs remote from their organ of primary secretion. Examples of the endocrine system in biology follow:

Gland Hormone Physiology

With regard to breast function, at birth the breast is just a little nipple bud with essentially no function. At puberty, the breasts begin to enlarge, under the influence of the hormones oestrogen and progesterone.

The hormonal flux associated with the menstrual cycle is dependent on oestrogen and progesterone levels. During pregnancy, the pituitary secretes the hormone prolactin (luteotrophic hormone) which initiates and stimulates milk production (lactogenesis). This prolactin hormone is stimulated by oestrogen and inhibited by progesterone. With the disappearance of the corpus luteum of pregnancy and the expulsion of the placenta, the levels of progesterone drop precipitously. Thus the unopposed action of oestrogen stimulates prolactin production, which in turn stimulates the formation of milk (Fig 2.6). The feeding baby, by its sucking action on the nipple, expresses milk from the breast ducts, but it cannot get at the milk lying deep within the aveoli. Here again another hormone, called oxytocin, comes into action. Stimulation of the nipples by sucking sends nerve impulses to the brain (hypothalamus). The brain in turn activates the pituitary to produce oxytocin, which reaches the breast via the blood stream.

The woman's monthly "periods" are again harmoniously controlled. The breasts also enlarge premenstrually and occasionally become painful. This is called cyclical mastalgia. This pain disappears with the onset of menstruation, as the breast contracts.

Shape and form

The shape and form of the breast is basically determined by the genes and is thus inherited. The factors that determine the appearance of the breast are:

• The amount of fat in the breast. The glandular tissue is similar in small and large breasts. It is mainly the fat that determines size. Thus losing weight by diet and exercise will probably decrease the size of the breasts to a certain extent.

• The shape of the breast is strongly influenced by the triangle of skin, which extends from the chin to fan out over the breast. This triangle of skin is supported by the fan shaped platysma muscle. This skin triangle together with its supporting fan shape platysma muscle is sometimes refelT8d to as the "natural bra~.

By exposing her lower teeth, the women contracts the platysma muscle, and this will lift the breast upwards (the natural bra effect).

• Coopers ligaments also contribute to breast firmness.

Thus by looking after the skin with a good skin oil or cream, and by doing the correct exercises (push ups and swimming are excellent breast toners), and finally by eating a healthy diet (see chapter 8), the condition of the breasts can be maintained to a certain extent.