The Parts of the Breast

Anatomy From Nipples to Areola to Montgomery Glands

The primary biological function of the female breast is to produce breast milk and breastfeed a baby. Breast anatomy is complex and intricate, involving various types of internal tissue, as well as milk ducts, lymph vessels, the nipple and areola, and other structures. Here's what to know about the many internal and external parts of the breast, their purpose, and the medical conditions that can affect them.

Female breast anatomy, illustration
PIXOLOGICSTUDIO/SCIENCE PHOTO LIBRARY / Getty Images

What Are Breasts Made Of?

The female breast is made up of three types of breast tissue, including:

  • Glandular: Glandular tissue contains the lobes and lobules that produce breastmilk.
  • Adipose (or fatty): Breast size is determined by the amount of fatty tissue in the breast.
  • Connective (or fibrous): This kind of tissue holds the glandular and fatty breast tissue in place.

Nipple

The nipple is in the center of the breast, surrounded by the areola. Each nipple contains about nine milk duct orifices through which breast milk flows.

Nipples are held erect by small, smooth muscles that respond to signals from your autonomic nervous system. Nipple erection can be caused by cold temperature or stimulation.

Conditions that affect the nipple

Paget's disease is a rare form of breast cancer that accounts for less than 5% of breast cancer cases. Cancer cells usually travel from the ducts of the nipples and spread to the nipple's surface and the areolas, causing them to become itchy, red, and scaly.

Sulcus

At the intersection of the areola and the rising edge of the nipple is a fold called the sulcus. It may be a smooth curve of skin, or it may look like a wrinkle. Inverted nipples may hide within the sulcus while retracted nipples may pull in at the sulcus line.

Areola

Surrounding the nipple is the areola, an area of skin that is darker than the rest of the breast skin. Your areola may be small or large, round or oval. During pregnancy, the areolas may grow in diameter, and may remain larger (and sometimes darker) afterward.

Small bumps on the areola may be either Montgomery's glands or hair follicles. You can usually tell the difference because hairs emerge from the hair follicles.

Condtions That Affect the Areola

If you notice a change in your areola skin, such as dimples, puckers, or a rash, check with your doctor. These might be harmless, but could also be symptoms of Paget's disease.

Symptoms of tenderness or a hard lump beneath the areola may also be a symptoms of asubareolar abscess, a non-cancerous infection that may need to be drained.

Montgomery Glands

Montgomery glands are small glands that lie just below the surface of your areola and may appear as small bumps in the skin. Also called areolar glands, these provide lubrication during breastfeeding as well as an odor that attracts the infant to the breast.

Conditions That Affect Montgomery Glands

Montgomery glands may become blocked, like pimples, and swell. A cyst may develop beneath a blocked gland, which can feel uncomfortable, but is not a sign of breast cancer.

Lobes

Each breast contains 15 to 20 lobes that contain clusters of lobules, which produce breast milk. Each lobe has 20-40 lobules.

Conditions that affect the lobes

Invasive lobular carcinoma (ILC) accounts for 10% to 15% of breast cancers. ILC starts in the breast’s lobules and invades surrounding tissue. ILC can manifest as a thick or full area that feels different than the rest of the breast.

Noncancerous conditions that can affect the lobes and lobules are lobular carcinoma in situ (LCIS) and atypical lobular hyperplasia (ALH). These are called neoplasias and consist of abnormal cells. Though neoplasias are not cancerous themselves, having them raises your risk of breast cancer in the future.

Glandular tissue includes the lobules, which produce breast milk, and ducts, the tubes that carry milk to the nipple.

Milk Ducts

Milk ducts are small tubes that transport milk from the milk glands (the lobules in the breast) out the tip of the nipple. Ducts are lined with myoepithelial cells. 

Breast milk is released from tiny holes at your nipple's surface called milk duct orifices. There are typically two or three of these holes in the center of your nipple, and three to five more arranged around the center. These holes have tiny sphincters (valves) that close to prevent leakage when you are not breastfeeding.

The ducts just below your areola widen before they enter your nipple. This wide, sac-like area is called an ampulla. Sometimes the ampullae are called frontal ducts.

Conditions that affect the milk ducts

Invasive ductal carcinoma originates in the milk ducts; it is the most common type of breast cancer, accounting for 80% of cases. Ductal carcinoma in situ, which also originates in the ducts, is an noninvasive form of ductal cancer. A ductogram or the Halo test may be used to examine breast fluid or ductal cells.

During breastfeeding, a milk duct can become plugged, leading to an infection called mastitis. Mastitis can be very uncomfortable, but usually responds well to heat and antibiotics.

Blood Vessels

The internal mammary artery, which runs underneath the main breast tissue, is the primary source of the breast's blood supply. The blood supply provides oxygen and nutrients to the breast tissue.

Conditions that Affect the Blood Vessels

With a nipple-sparing mastectomy, a surgeon may temporarily remove and then replace the nipple in order to remove any breast cells that may contain cancer. This can, however, disrupt the tiny blood vessels, leading to loss of your nipple later on, so it is essential that the blood supply in the nipple be preserved to keep these tissues alive.

Lymph Vessels

Lymph vessels transport lymph, the fluid that helps your body’s immune system fight infection. Lymph vessels connect to lymph nodes found under the armpits, in the chest, and elsewhere in the body.

Conditions That Affect the Lymph Vessels

A rare but aggressive type of breast cancer, called inflammatory breast cancer (IBC), occurs when cancer cells block lymph vessels in the skin, causing the outer breast to look inflamed. Symptoms of IBC include dimpling or thickening of breast skin and may look and feel like an orange peel. Other symptoms include breast swelling, itching, and skin that is red or purple.

The breast's lymph system is also significant in the diagnosis and treatment of breast cancers in general. When cancer cells are found in the lymph vessels, they are capable of moving through the bloodstream, into the lymph nodes, and spreading to other organs, a phenomenon known as metastasis.

Nerves

Your breasts contain a rich network of nerves, with sensitive nerve endings especially plentiful in the areola and nipple. These nerves make the breasts sensitive to touch, cold, and a nursing baby. When your baby begins suckling at your breast, it stimulates nerves to release milk from your milk ducts. This called the "let-down reflex" and can cause a tingling sensation.

Muscles and Ligaments

Your breasts lie on top of the pectoral muscles, which extend from the breastbone up to the collarbone and into the armpit. Their main purpose is to control movement in your arm and shoulder, but they are also connected to the breasts.

The breasts themselves do not contain any muscles. Instead, they are supported by a framework of fibrous, semi-elastic bands of tissue called Cooper's ligaments, which form a "hammock" for your breast tissue to keep its shape. These ligaments run from your collarbone and chest wall throughout the breast and up to the areola skin. With age, these ligaments often stretch, causing the breasts to sag.

Hair Follicles

Hair follicles are present on the outer breast, usually on the surface of your areola. Due to these follicles, it is not unusual to have a few hairs growing on the surface of your areola or breast skin. If these are bothersome, carefully trim them. Pulling them out with tweezers can be painful and may open the way to infections.

A Word From Verywell

The female breast is a complex organ. Understanding its anatomy and which parts perform certain functions is helpful if you choose to breastfeed, as you will be able to recognize sensations (such as the let-down reflex) and understand how milk production works. It is also important to become familiar with your breasts so you can determine what's normal for you and what's not.

If you are concerned by any changes in how your breasts look or feel, get in touch with your doctor for an evaluation.

Frequently Asked Questions (FAQs)

What parts of the breast produce milk?

Milk is produced in the lobules of the breast. From there, the milk travels through the milk ducts to the nipple.

What type of breast tissue can develop cancer?

Most breast cancers originate in the glandular tissue, which contains the milk ducts, lobes, and lobules. Other areas of the breast that can be affected by cancer include the nipple and areola, but these cancers are rare.

What is the hard part in your breast called?

The firm part of the breast consists of fibrous connective tissue, which is normal. If you feel an unusual lump or hard area in your breast, however, contact your doctor.

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Article Sources
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Additional Reading