Breast anatomy includes the nipple and areola on the outside, and milk ducts, lobes, lobules, lymph nodes, and vessels on the inside. Normal breasts can range in size, shape, appearance, and texture and may change throughout life.
The primary function of the female breasts is to produce breast milk and breastfeed a baby. Breasts can also play a role in female sexuality and pleasure.
When to see a healthcare provider
Changes to your breasts always warrant a visit to your healthcare provider. These include:
- A new lump in the breast
- Nipple discharge
- Changes in the appearance of the skin
- A rash
- A nipple that turns inward
- New or unusual pain in the breast
What Are the Layers of the Breast?
The female breast is made up of multiple types of tissue, including:
- Glandular:Contains the lobes and lobules that produce breast milk
- Adipose (fat tissue):Responsible for the size of the breasts
- Connective (or fibrous):Holds the glandular and fatty breast tissue in place
What area of the breast do most breast cancers develop?
Most breast cancers develop in the upper part of the breast close to the armpit.
Breast Anatomy
The female breast contains many different parts with varying functions.
Nipple
The nipple is in the center of the breast, and it's surrounded by the areola. Each nipple contains milk duct openings 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.
Paget's disease of the nipple is a rare form of breast cancer that accounts for less than 5% of breast cancer cases. In this condition, cancer cells usually travel from the milk ducts and spread to the nipple's surface and the areola, causing them to become itchy, red, and scaly.
What parts of the breast hurt during early pregnancy?
The entire breast may be uncomfortable in early pregnancy. As hormones are changing the breasts and preparing them for milk production, the skin, lobes, and nipples may all feel uncomfortable. As the breast size increases, the ligaments in the breast stretch and may feel painful.
Areola
Surrounding the nipple is the areola, an area of skin that is darker than the rest of the breast. The average areola size is 2.5 inches in diameter, but they may be small or large, round or oval. All of these variations are normal.
During pregnancy, the areolas often grow in diameter and may remain larger (and sometimes darker) even after pregnancy. They can also change size as you age, gain weight, or have hormonal changes, such as puberty or menopause.
There are small bumps on the areola. These are either hair follicles or Montgomery glands, which are sebaceous (oil) glands.
If you notice any changes in the areola, such as dimples, puckers, or a rash, notify your healthcare provider. These might be harmless, but could also be symptoms of Paget's disease.
Tenderness or a hard lump beneath the areola may also be symptoms of a subareolar abscess, cancer, or a noncancerous infection that may need to be drained.
Montgomery Glands
Montgomery glands aresmall glands that lie just below the surface of the areola and look like small bumps on the skin. Also called areolar glands or Montgomery tubercles, these provide lubrication during breastfeeding and have a scent that attracts the infant to the breast.
Montgomery glands may become blocked, like pimples, and become swollen. A cyst may develop beneath a blocked gland. This can feel uncomfortable, but it is not a sign of breast cancer.
Lobes
Each breast has 15–20 lobes that contain clusters of lobules, which produce breast milk. Each lobe has 20–40 lobules.
Invasive lobular carcinoma (ILC) accounts for 10% of breast cancers. ILC starts in the breast’s lobules and invades surrounding tissue. ILC can feel like 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 consist of abnormal cells. Though they aren't cancerous themselves, having them raises your risk of breast cancer in the future.
Glandular tissue includes thelobules,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 to the tip of the nipple.
Breast milk is released from tiny openings at the surface of the nipple. 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 (rings of muscle) that close to prevent leakage when not breastfeeding.
The ducts just below the areola widen before they enter the nipple. This wide, saclike area is called an ampulla.
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.
Breast cancer can also occur in the milk ducts. Cancer beginning in the milk ducts is called invasive ductal carcinoma. Most breast cancers (around 80%) start in the milk ducts. Ductal carcinoma in situ, which also originates in the ducts, is a noninvasive form of ductal cancer.
Are breasts part of the reproductive system?
Although breasts are not reproductive organs, they have an important function in reproductive health, as they are able to produce milk to nourish an infant.
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. Other blood vessels include the thoracoacromial artery, lateral thoracic artery, as well as capillaries and veins.
During 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. Maintaining the blood supply in the nipple helps to keep these tissues alive after a mastectomy.
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.
A rare but aggressive type of breast cancer, called inflammatory breast cancer (IBC), occurs when cancer cells block lymph vessels in the skin, which then causes inflammation in the breast. 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 breast skin that is red or purple.
The breast's lymph system plays a role in the diagnosis and treatment of breast cancers overall. Cancer cells can travel through lymph vessels into the lymph nodes, move through the bloodstream, and spread to other organs, leading to metastasis.
Nerves
Breasts contain a network of nerves, with many sensitive nerve endings found in the areola and nipple. These nerves make the breasts sensitive to touch, cold, and a nursing baby. When a baby begins nursing, nerves are stimulated to release milk from the milk ducts. This is called the let-down reflex and can cause a tingling sensation.
Sometimes after a mastectomy, when the full breast has been removed, there can be nerve pain or discomfort that remains, called post-mastectomy pain syndrome. This can cause numbness or tingling in the wall of the chest and occurs due to changes in the nerves that occur after surgery.
Muscles and Ligaments
The 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 the 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 bands of tissue called Cooper's ligaments, which form a "hammock" for the breast tissue to keep its shape. These ligaments run from the collarbone and chest wall throughout the breast and up to the areola. The ligaments can stretch over time, causing the breast to sag.
"Mastalgia" is a term that means breast pain, and this can have many causes. One type of pain is referred pain, which feels like the breast hurts but is actually caused by inflammation or injury to the muscular chest wall under the breast. Another cause of mastalgia can be pain from the ligaments in the breast as they are being stretched.
Hair Follicles
Hair follicles are present on the outer breast, usually on the surface of the areola. Due to these follicles, it is not unusual to have a few hairs growing on the areola or breast skin.
A condition called folliculitis can occur in the hair follicles. With folliculitis, the follicle around the hair becomes inflamed and may be red, swollen, and painful. A boil can form if an infection in the inflamed follicle goes deeper into the surface.
What are the areas of breast pain?
Pain can be felt anywhere on the breast, but the most common type of breast pain is cyclical. This type of pain is related to the menstrual cycle and may be felt around the time ovulation until the start of your period. You may feel it in one or both breasts or in your underarm.
Physiology of the Breast
The primary function of the breasts is to produce milk for feeding an infant. This function is driven by female hormones, including:
- Estrogen, which prepares the milk ducts to carry milk
- Prolactin, which prepares the glands to produce milk and promotes the production of progesterone
- Progesterone, which increases the size and number of lobules in the breast
- Oxytocin, which helps release milk during latching
Dense Breasts
Dense breasts are breasts that have more glandular tissue than what is average. Dense breasts are normal, but they are associated with slightly higher chances of developing breast cancer. Dense breast tissue also makes it harder to see breast cancer on a mammogram.
Male Breasts
Male breasts develop from the same cells as female breasts. Male breasts, however, have underdeveloped milk ducts. Males can develop a condition called gynecomastia, which causes enlargement of the breast tissue.
Summary
The outer part of the female breast includes the nipple and areola. Milk ducts, lobes, lobules, lymph nodes, and vessels are located on the inside of the breast.
The female breast produces milk to feed an infant, but it also plays a role in female sexuality. Many conditions can affect the breast, including cysts, mastitis, and different types of breast cancer.
