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Anatomy of the Breast

The breast is made up of several structures including breast tissue and fat. It also contains blood vessels, lymphatic vessels, nerves and connective tissue.

Breast Tissue:
The breast tissue is composed of 15 to 20 breast lobes of which are further divided into smaller lobules. The lobules produce milk during pregnancy and lactation. The breast tissue also includes the mammary ducts. These are small conduits that carry the milk from the lobules to the nipple during lactation. There are between 5 to 10 ductal systems in each breast opening at the nipple.

Connective Tissue:
The connective tissue is also called the stroma. This tissue supports the breast elements including the ducts and lobules. There are ligaments that stretch from the chest wall muscle to the skin which hold the breast in place (Cooper’s ligaments). The lymphatic and blood vessels are located within the stroma. Breast cancer cells limited to the ducts is defined as a ductal carcinoma in situ. The presence of cancer cells extending beyond the ducts into the stroma is defined as an invasive carcinoma. Once in the stroma, cancer cells can spread to other parts of the body through the lymphatic or blood vessels.

Blood Vessels:
The breasts also have blood vessels. There are different types of blood vessels including veins, arteries, and capillaries. The arteries bring blood with oxygen to the breast tissue. The arterial and venous system connects through the capillaries. The lymphatic fluid is produced at this level and taken to the lymphatic system. The veins carry blood back to the heart and lungs to get oxygen.

Lymphatic System:
The lymphatic system is an essential component of the immune system. It blocks the spread of infections, diseases, and cancer. The lymphatic vessels are distributed throughout every square inch of the body including the breasts. They drain lymph, which is a clear fluid produced in the tissue. This fluid carries damaged cells, dead cells, foreign bodies, bacteria and all substances your body does not need and want out. It can also carry cancer cells. This fluid is brought into the lymph nodes where it concentrates all these materials and they are essentially eaten up and destroyed by immune cells. The lymph nodes draining the breast are located in the axilla, behind the chest bone and above the collarbone. Once in the lymph nodes the fluid gets filtered and cleansed before joining the circulatory system in the neck area.

Fatty Tissue:
The breasts are also composed of fatty tissue. The fatty tissue content increases as women age. After menopause most of the breast glandular tissue atrophy and get replaced with fat.

Muscle:
There is muscle tissue surrounding the lobules that help to squeeze milk into the ducts. There is also muscle tissue around the nipple. The chest muscle underneath the breast is called the pectoralis major. This muscle is surrounded by an envelope of thin tissue. This tissue separates the muscle from the breast. It is called the fascia.

Effect of Aging in the Breast Tissue:
At the time of puberty the breast grow due to hormonal stimulation. The breast lobules and the ductal system become mature. They develop and grow further during pregnancy.When women reach their menopause the ovaries stop producing hormones. As a consequence, there is loss of breast glandular tissue. The breast lobules atrophy and decrease in number. The glandular tissue is replaced by less dense fatty tissue. As a result, the breast density diminishes.