Breast Anatomy

What are breasts?

Breasts are part of the female and male sexual anatomy. For women and people assigned female at birth (AFAB), breasts are both functional (for breastfeeding or chestfeeding) and sexual (bringing pleasure). For men and people assigned male at birth (AMAB), there isn’t a physiological function. However, a man’s breasts can still provide sexual pleasure.

The visible parts of your breast anatomy include your nipples and areolas. Most people are born with two breasts.

What are the three layers of a woman’s breast?

Several kinds of tissue form the breasts of women and people AFAB. Muscles connect your breasts to your ribs. The three different types of breast tissue in women include:

• Glandular: Also called lobules, glandular tissue produces milk for lactation.
• Connective or fibrous: This tissue holds glandular and fatty breast tissue in place.
• Fatty: This tissue fills in the areas between glandular and connective tissue and determines your breast size.

Men and people AMAB have gynecomastia glandular tissue and fatty tissue. Their glandular tissue contains underdeveloped milk ducts.

What is the anatomy of the breasts?

There are many different parts to female breast anatomy, including:

• Adipose tissue: Your breast is mainly made up of fatty tissue (adipose tissue). It extends from your collarbone to your armpit and across your ribcage.
• Lobes: Each breast has between 15 to 20 lobes, or sections. These lobes surround your nipple like spokes on a wheel.
• Glandular tissue (lobules): These small sections of tissue found inside lobes have tiny bulblike glands at the end that produce milk.
• Milk (mammary) ducts: These small tubes, or ducts, carry milk from glandular tissue (lobules) to your nipples.
• Nipples: The nipple is in the center of your areola. Each nipple has about nine milk ducts, as well as hundreds of nerves.
• Areolae: The areola is the circular darker-colored area of skin surrounding your nipple. Areolae have glands called Montgomery’s glands that secrete a lubricating oil. This oil protects your nipple and skin from chafing during breastfeeding.
• Blood vessels: Blood vessels circulate blood throughout your breasts, chest and body.
• Lymph vessels: Part of your lymphatic system, these vessels transport lymph, a fluid that helps your body’s immune system fight infection. Lymph vessels connect to lymph nodes, which are found under your armpits, in your chest and in other places.
• Lymph nodes: Small organs that help fight infection.
• Nerves: Nipples have hundreds of nerve endings, which makes them extremely sensitive to touch.

What is the anatomy of a male breast?

Men and people AMAB have breasts, too. During puberty, the hormone testosterone usually stops breasts from developing as they would in a woman or person AFAB. On the outside, men have nipples and areolae. Internally, they have undeveloped milk ducts and no glandular tissue. Male breast problems can include gynecomastia, a benign condition that causes the breasts to enlarge, and very rarely, breast cancer.

What are the physiological functions of the breast?

Female hormones — namely, estrogen, progesterone and prolactin — play a key role in breast development and function. The main role of the breasts is to produce human milk.

• Estrogen stretches milk ducts and helps them create side branches to carry more milk.
• Prolactin promotes the production of progesterone and prepares glands for milk production.
• Progesterone increases the number and size of lobules in preparation for breastfeeding. This hormone also enlarges blood vessels and breast cells after ovulation.
• Oxytocin helps release (or eject) breast milk.

What conditions and disorders affect breast anatomy?

Breast cancer is the number one threat to breast health. Approximately 1 in 13 women and people AFAB will receive a breast cancer diagnosis in their lifetime. Other conditions that affect breast health include:

• Benign (noncancerous) breast disease.
• Breast cysts.
• Breast lumps.
• Breast pain (mastalgia).
• Breast rash.
• Fibrocystic breast changes (noncancerous lumps and tenderness).
• Mammary duct ectasia (swollen milk ducts).
• Mastitis (breast infection).
• Nipple discharge.

What are dense breasts?

Your mammogram report may note that you have dense breasts. Dense breasts have more glandular and fibrous tissue and less fatty tissue. Dense breast tissue and tumors both look white on mammograms, making it more difficult to detect breast cancer. Up to half of women and people AFAB between the ages of 40 and 74 have dense breasts. The condition isn’t related to breast size, look or feel. People with very dense breasts have a slightly higher risk of breast cancer. Talk to your healthcare provider about your risk for breast cancer based on your breast density.

How can I keep my breasts healthy?

As breast cancer is a top concern, talk to a healthcare provider about when and how often to get mammograms. Recommendations vary depending on risk factors, such as family or personal health history. Breast self-exams can help you get familiar with how your breasts look and feel so you’re more likely to notice changes in your breasts.

What part of the breast is most sensitive?

Your nipples contain hundreds of nerve endings. Generally, a female breast is more sensitive to stimulation due to hormones. However, males can also experience pleasure from the nerve endings in their nipples.

When should I call my healthcare provider?

You should call a healthcare provider if you experience:

• Newly discovered lump in your breast.
• Nipple discharge.
• Breast pain.
• Changes in the way your breast or skin looks or feels.
• Nipple that suddenly turns inward (inverted nipple).
• Breast rash.

If anyone in your biological family has received a breast cancer or ovarian cancer diagnosis before age 50, talk to a healthcare provider about genetic testing or earlier mammogram screenings.

A note from Cleveland Clinic

Female breasts can produce milk for breastfeeding (chestfeeding) and serve as an erogenous (pleasure) zone. Males also have breasts, but they don’t serve the same purpose. The tissues in your breasts can become cancerous. Regular mammograms, or breast screenings, can help detect cancer early when it’s most treatable. Call your healthcare provider anytime you notice a change in the way your breasts look or feel.