What to know about breast anatomy

The breasts lie on top of the chest wall and over the pectoral muscles. They contain glands, lobules, fatty tissue, and other structures. Milk ducts lead to the nipples, which are surrounded by a darker area called the areola.
Both males and females have breasts, but they are more developed in females.
Each breast contains many glands and other structures that allow them to perform their functions. Namely, the primary biological function of the breast is to produce milk to feed infants. However, the breast can also be a symbol of femininity and play a role in sexual attraction and pleasure.
Breast cancer is a type of cancer that begins in the breast. Other than skin cancer, it is the most common cancer in American women, and while much rarer, can also occur in men. Awareness of the symptoms and the need for screening are important ways of reducing the risk of breast cancer.
Breast cancer
most common
much rarer
men
In this article, we will explore the various components that comprise male and female breasts. It will also discuss how a person can perform a self-examination for breast cancer.
Sex and gender exist on spectrums. For the purposes of this article, we use “male” and “female” to refer to a person’s sex assigned at birth. Learn more.
Learn more.
Breast definition
Share on Pinterest
The breasts are glandular organs that sit atop the chest wall and pectoral muscles. The breasts are present in both sexes. However, the female breasts are more developed. The breasts are also an important component of the female reproductive system.
When puberty occurs, the female breasts develop at an accelerated rate due to the effects of estrogen and other hormones. These result in the development of adipose (fatty) tissue that gives the female breasts their hemispherical shape, as well as the development of glandular tissue and the duct system.
puberty
The male breast structure is nearly identical to the female breast. However, they usually lack the specialized structures that allow female breasts to produce and secrete milk. In some cases, men may develop a condition known as gynecomastia. This is where the mammary glands enlarge and resemble female breasts.
gynecomastia
Function of breasts
The primary function of the female breasts is to produce milk for breastfeeding. During pregnancy, the hormone prolactin stimulates milk production, while the hormone oxytocin stimulates the release of milk from the glands. The female breast also has a sexual function, as stimulation of the breasts or nipples may enhance pleasure.
primary function
In males, the breasts do not have a functional role. However, they may also enhance sexual pleasure following manipulation of the breast and nipples.
Anatomy of the breast
Click on the BodyMap above to interact with a 3D model of the breast.
Breast structure
Different structures make up the breasts, including structures underneath the skin. These structures include:
include
The chest wall includes the bones, skin, fat, muscles, and various other tissues that protect the organs between the neck and the abdomen.
includes
The bones that make up the chest wall include the ribs, the breastbone (which a person can feel in between the breasts), and the spine. It also helps to support breathing and the movement of the upper arms and shoulders.
The pectoral muscles make up the chest muscles. They are present underneath the breasts and provide support. The pectoral muscles include:
pectoral muscles
pectoralis major
pectoralis minor
serratus anterior
subclavius
The lobules are glands that are responsible for producing milk in the breast. The lobules are in clusters and form lobes.
There are between 15–20 lobes embedded in the breasts’ fatty tissue, and they radiate around the nipple. Some breast cancers start in the lobules and are known as lobular cancers. Male breasts typically lack lobules, as they do not produce milk.
15–20 lobes
lobular cancers
The ducts are the tubes that carry milk from the lobules to the nipple. A collection of lobules along with a duct form the terminal ductal lobular unit. There are many terminal ductal lobular units present in the breast. Most breast cancers start in the terminal ducts and are known as ductal cancers.
The mammary glands are accessory glands present in the chest with specialized functions. It is an apocrine type of gland and its main function in females is to secrete milk.
The mammary glands are predominantly located in the pectoral region of the chest. However, a part of the mammary gland, known as the axillary tail, extends to the axilla, which is the region below the armpits.
Fatty tissue, along with fibrous tissue, makes up the connective tissue that holds all the structures within the breasts in place. The fatty tissue fills the space between glandular (lobes and ducts) and fibrous (ligaments) tissue.
The fatty tissue determines the size of the breast. During puberty, increased estrogen levels stimulate the buildup of fatty tissue and glandular tissue which increases the size of the female breast.
The lymph nodes are small organs present throughout the body. The lymph nodes produce a fluid called lymph which contains lymphocytes. Lymphocytes are immune cells that fight infections and diseases. Lymph vessels transport filtered lymph fluid from the breast to the lymph nodes.
lymph nodes
The axillary group of lymph nodes drains 75–80% of the lymph from the breasts. These lymph nodes are present in the underarm region. The internal mammary group of lymph nodes drains the remaining 20–25% of lymph. These nodes are present in the breast region.
75–80%
20–25%
The areola is the darker, pigmented, round area around the nipple. The areola has small bumps on its surface. These are sebaceous glands that release oily secretions that stop the areola and nipple from cracking.
The nipple is the raised projection in the middle of the areola. About 15–20 ducts connect to the nipple. The nipple provides an exit for milk release during breastfeeding. The nipple also contains smooth muscles that can cause the nipple to become erect.
15–20 ducts
Checking for breast cancer
Breast cancer occurs when cells in the breast grow at an uncontrollable and accelerated rate. This can be due to mutations or changes in the genes that control the growth of breast cells. Breast cancer can spread to other regions of the body through the blood or lymph.
According to the American Cancer Society, breast cancer is the second leading cause of cancer death in women after lung cancer. The lifetime risk of getting breast cancer is about 1 in 833 for men.
second
1 in 833
Breast cancer treatment is more likely to be successful if a person can detect the cancer early. People can self-examine their breasts regularly to increase the likelihood of early detection.
more likely
Both men and women can do similar self-examinations to check their breast health.
A person should start by first examining their breasts in a mirror with their shoulders straight and their arms on their hips. They should check that their breasts are their usual size, shape, color and that the breasts are evenly shaped.
People should look for changes such as:
dimpling, puckering, or bulging of the skin
changes in the position of the nipple or if the nipple is inward instead of sticking out
redness
a rash
swelling
soreness
Next, the person should raise both arms and look for the same changes. They should also check to see if any fluid comes out of any or both nipples.
The person should then lie down and examine their breast with their hands. To examine the left breast, a person should use their right hand and vice versa for their right breast.
They should examine the breast using a circular motion, starting at the nipple, and then fanning out in a circular motion, ensuring they reach their collarbone, upper abdomen, and the underarm region. A person should apply firm enough pressure to feel any lumps.
Lastly, the person should repeat the previous step while standing up.
If a person notices any changes, finds a lump, or experiences discharge from the nipple, they should seek advice from their primary care physician. A doctor will be able to check and order tests to ensure a correct diagnosis.
Click here to learn more about performing a self-examination for breast cancer.
Click here to learn more about performing a self-examination for breast cancer.
Summary
The breasts are glandular organs present in the chest area of the upper body. They consist of specialized structures, including lobules and ducts, that facilitate milk production in females and are usually non-functional in males.
Breast cancer can occur in males and females. Therefore, it is vital for people to perform regular self-examinations to check for breast cancer. This includes visually examining the breast as well as manually examining the breast in a circular motion for lumps or skin changes. Early detection may help treat possible breast cancer more successfully.