Breast’s Anatomy: What Makes Up a Breast?

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Breasts are milk-producing (mammary) glands surrounded by fat and are attached to the front of the chest by ligaments. The breast rests on the pectoralis major chest muscle, but has no muscle tissue itself. The fat in the breasts determines their shape and size, which varies among women even though the size of the mammary gland system is relatively standard. In addition, women commonly have one breast that is larger than the other.

Breasts begin developing between the ages of 9 and 14 for most girls, and signal the start of puberty. Breast tissue is highly sensitive to the hormones estrogen, progesterone, and prolactin throughout the menstrual cycle. While breastfeeding, prolactin triggers milk production within the breast, and its anatomy is simple yet complex.

Lobules, Alveoli, and Ducts

Breasts have 15 to 20 sections known as lobes or lobules that converge at the nipple. Each lobule consists of hollow sacs called alveoli, and the lobules are connected through ducts. The final collection area for milk is known as the main duct.

During breastfeeding, prolactin stimulates the alveoli to pull nutrients from the woman’s blood to produce breast milk, and oxytocin causes the alveoli to release the milk through the mammary ducts to the nipple.


Also known as the mammary papilla, the nipple is the outlet for the mammary ducts and where milk is secreted.


Often included when referring to the nipple, the areola is the round pigmented area surrounding the nipple. During breastfeeding, small bumps on the areola known as Montgomery glands produce an oily substance that cleans and lubricates the nipple.

Lymph Nodes and Ducts

The lymphatic system helps fight infection by capturing and excreting pathogens and toxins through lymph nodes and ducts. These nodes are found near the breast, in the armpit, and behind the breastbone. Often, axillary (armpit) lymph nodes are removed during mastectomy.

Cooper’s Ligament

This ligament is often called “nature’s bra” because it lifts the breast and prevents it from sagging.

For a slideshow on breast anatomy, visit

Have questions about breast cancer? Visit our blog’s Ask the Doctor section.

Weird Breast Issues That Aren’t Really Weird At All

breast changesFrom nipple leakage to uneven sizes, our breasts often confuse or scare us. Most of the time, what appears to be a breast problem isn’t a problem at all, but a completely normal occurrence. Breast information isn’t at the forefront of the news unless it’s connected to cancer, so we don’t receive much information about breast issues that aren’t serious.

The following breast issues are typically normal, even though they may seem odd. Let us stress that if you have questions about any breast issue, or feel that something isn’t right, do not hesitate to call your doctor. Always listen to your gut and intuition.

Uneven breast sizes

If you look closely at other parts of your body that come in pairs, such as your eyes, hands, and feet, you’ll see that each one of the pair is different from the other, and this includes your breasts. Some women may find that one breast is a size or two different from the other, and this is normal.

Lumpy breasts

Have you ever driven yourself crazy because you think you’ve found several lumps during a self-exam? This one can be scary, but for some women, lumps are a normal part of their breast tissue. Called fibrocystic breasts, this noncancerous condition is very common, especially among premenopausal women. Dense breast tissue tends to feel lumpy, which is one more reason to know what is normal for your breasts and do thorough monthly self-exams.

Nipple leakage when you’re not pregnant

Nipple leakage is common, and fluid can be almost any color or consistency. Some women experience spontaneous leakage, while for others, the leakage occurs only if the nipple is stimulated. Rarely, leakage signals something more serious, so check with your doctor if you’re concerned or it regularly occurs spontaneously.

Extra nipples

Some men and women are born with extra nipples, much as female animals have. According to Texas ob-gyn Michael Yang, MD, when a fetus forms, it has a milk line with several nipples that runs from the armpits down to the groin. Extra nipples typically disappear before birth, but some don’t, and their appearance ranges from molelike to actual miniature breasts.

Menstrual cycle-related breast changes

Thank your hormones for those breast changes during the month. Estrogen and progesterone increase and decrease during your cycle, which can cause breast tenderness and nipple soreness. If your breasts are unbearably sore, ask your doctor for advice on nutritional support.

Weight gain or loss from breasts

Speaking of breast changes, women often lament the fact that when they lose weight, it comes from their breasts first. Because breasts are mostly fat, it’s normal for them to change size when you lose weight.

Again, call your doctor with any breast-related concerns or questions.