The Anatomy of the Breasts

anatomy of the breasts

The various structures which make up breast tissue are listed as follows:

  • Arteries, which branch into tiny arterioles, bring fresh blood rich in oxygen and nutrients.
  • Veins, which are closer to the surface, remove the used blood, and waste products of metabolism.
  • Nerves, which branch into tiny nerve endings, increase the sensitivity, especially in the nipples.
  • Lobules, which are part of the mammary gland tissue, produce milk.
  • Ducts, which are the other part of mammary gland tissue, bring milk to the nipples.
  • Muscle fibers, which line the lobules and ducts, squeeze out the milk.
  • Connective tissue, which is woven throughout the breasts, made up the support system.
  • Fat, which plumps up the breasts, is woven throughout the mesh of connective tissue.
  • Erectile fibers, which are in the areola-nipple complex, respond to erotic stimulation.
  • Lymph channels, which are part of the immune system, drain breast tissue of extra fluid.

The Squeeze Syndrome

In one study, women of varying ages had breast pumps attached to their nipples. When the breasts were gently squeezed for a sufficiently long time, 83 percent of the women produced some milky fluid, whether they were young, old, mothers, previously pregnant, or never pregnant. Squeezing sends a message to the pituitary gland in the brain, which translates this into a call for prolactin. Prolactin is the hormone that stimulates the breasts of a nursing mother to produce more milk. The more her baby sucks at her breasts, the more milk is produced. Milk is synthesized, not from blood, but from the nutrients carried by the blood.

During nursing, the breasts will start leaking if the mother only thinks of her baby. She cannot stop this; she can only try to stop thinking of her child. The fibers lining the milk ducts are smooth muscle, like the fibers for nipple erection. They are not under the control of the conscious will. These two kinds of muscles are the only ones in the breasts.

Keep in mind that if the nipples are squeezed for long enough, they will produce fluid.

The Mature Breast

  • At puberty: The duct tissue grows and branches out like the twigs of a young tree, forming lobule buds. The connective tissue grows and spreads in a network, and fat builds up within the mesh. The breasts feel dense, very firm, and packed with lobules and ducts.
  • At pregnancy: The breasts grow rapidly. Breasts that were almost flat will also grow to a very large size. The areola-nipple complex darkens, and the nipples become more erect. The blood supply increases and the veins become more noticeable.
  • After childbirth: Breast tissue returns to its pre-pregnancy state. But the areola-nipple complex stays larger, and the darker pigment remains. The veins also remain noticeable, a delicate bluish tracery running lightly across the breasts.
  • At menopause: The gland tissue shrinks to nearly its pre-puberty state. In under-weight women, breast size can shrink considerably. In women who put on weight, though the breasts increase in size, the contents are mainly fat tissue.

At each stage of a woman’s reproductive life, the breasts respond to estrogen output. They also respond each month after mid-cycle, when there are breast swelling and tenderness before a period.

To Bra or Not to Bra?

The average weight of each breast is between 150 and 200g. This increases to 400 to 500g during nursing. The combined breast weight of the average C-cup bust is 8 to 16 pounds. With the average D-cup, the weight is 15 to 23 pounds. With a DD-cup, it can be 30 pounds. Women who are full-figured appreciate the comfort and support of a well-fitting bra, as do nursing mothers. The debate is for women with neat pert breasts, for younger women, for all-size women who cannot find a bra which really fits without pinching or riding up, or without the straps digging into the shoulders and underarms.

Some smaller breasts, even when supported by a bra, drop early in life. Some larger breasts remain high and pert with no bra support. It seems to be the luck of the genes. The majority of women wear bras; they accept that the force of gravity could have some effect on their breasts. “The pull from a hanging breast…”

Some suggestions for wearing a bra include: if the breasts weigh over a pound each if the lower part dips to touch the chest wall when taking exercise, during pregnancy, and while nursing.

The findings from one study suggest that 7 out of 10 women have fitting problems with bras. The general recommendation is to have a cup size measured by a bra-fitting specialist every few years. Though the body weight can stay the same the distribution of breast tissue changes. The following tips might be useful when considering buying a new brassiere:

  • A bra should feel comfortable when fastened on the middle hook.
  • The breasts should be separated and completely contained within each cup.
  • The cups should fit snugly over the breasts, with no pleating or creasing.
  • The straps should be wide enough to protect against shoulder strain.
  • Once the straps are adjusted, they should neither slip off the shoulders nor dig into them.
  • The bust line should rest midway between the shoulders and elbows.
  • The band should fit snugly under the bust line, and not cause a midriff bulge.
  • The elastic should provide enough “give” to allow for easy movement without digging or cutting.

Breast Skin

Study the skin of the breasts. Become familiar with the size, shape, texture, and colour of any moles, freckles, or lumps. In teen girls, these are few. As time passes, most skins tend to get a little freckly, and more moles appear. Bras and moles together make hazardous conjunction. This is because a bra, no matter how well-fitting, can rub the mole if it is at the shoulders, and cause friction if it is under the breasts or across the back.

  • Regular friction is an irritant.
  • Irritants can be carcinogens (cancer-causing substances).
  • Carcinogens are serious hazards in areas of constant friction:

Check to make sure there is no mole along any of the bra straplines. Some physicians consider it is a preventive health measure to remove any mole which is on the line of a bra strap before it can give trouble. This is an issue of personal choice. If deciding against removal, avoid anxiety with the decision. Forget the mole. Simply check at regular intervals for the following:

  • Any change in the shape, size, or thickness of the mole.
  • Any redness surrounding the area.
  • Any inflammation near or actually on the mole.
  • Any alteration in its colour or texture.
  • Any new mole or other growth which suddenly appears.

Consult the physician promptly if any of the above occurs.

Pimples and spots on breast skin are fairly rare. But they can occur at the cleavage, and in the skin creases under the breasts. Take care that these areas do not become sites of infection. Check out personal hygiene. Daily washing with soap and warm water may not be enough. Increase this to twice a day.

Pimples and spots on breast skin can be treated like spots on the face or left to heal by themselves.

Tender Breasts

Each month, the breasts are prepared for a possible pregnancy. This phenomenon begins when the egg is released at mid-cycle. The tiny lobules swell up with fluid, and the breasts feel larger. In the week before the menstrual flow starts, even smooth breasts can feel lumpy, or grainy, or full of tiny bumps. There is a general feeling of heaviness and tenderness, the nipples tingle or itch. It has been estimated that this cyclic swelling causes discomfort in 50 percent of all women.

If no pregnancy occurs, the flow begins. The fluid in the lobules then drains away. The swelling, lumpiness, tenderness, and itching stop. The breasts return to their pre-period size, but they do not shrink back completely. Each month, there is a tiny increase in mammary development. This continues until about age 35. By then, it seems that the lobules and ducts have grown to their maximum (pre-pregnancy) size.

Keep in mind that breast tissue changes during each month.


Gynecomastia means “female-like breasts” in men. It happens to some degree in 50 percent of all boys at puberty and is due to the surges of the female as well as male hormones at this time. This type of gynecomastia is harmless and disappears within two years. However, the swellings can become large in boys who are overweight, and cause acute embarrassment. Gynecomastia can also occur in overweight men. A reduction in diet is the appropriate answer. Cosmetic surgery is another option.

A few men with no weight problems develop breasts as they age. This is due to a drop in testosterone production, so the effects of estrogen can show through.

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