Breast Anatomy and Function

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Breast Anatomy • How Breasts Change

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Breast Anatomy
Let's review the structure and function of the breast. Some of the terms like "lymph nodes" and "lobules" may be new to you, but they will help you
understand breast cancer treatment better.

Although the general shape of a breast is circular or teardrop, breast tissue can be found from the collarbone to the bra line, and from the breastbone to the armpit. That is why it is important for you and your physician to examine that entire area during breast examination.

Breasts are made up of milk-producing glands and milk-carrying ducts, imbedded in fatty tissue and fibrous supportive tissue. The glands are grouped in sections, called lobes. Each lobe has many smaller lobules that end in dozens of tiny grape-like bulbs where milk is produced. Slender tubes called ducts carry the milk from the lobes to the nipple. Most of the rest of the breast is composed of fatty tissue and fibrous supportive tissue.

Two muscles, the pectoralis major and the pectoralis minor, are attached to the ribs under the breast. One of these muscles may be cut to allow room for an implant. There are no muscles within the breast itself. The area of darker skin around the nipple is called the areola.

Arteries and veins carry blood to and from the breast, supplying it with nutrients and oxygen.

An important concept to understand is the lymphatic system. Lymph is the fluid that leaks out of the blood vessels and accumulates between cells. Lymph ducts collect this fluid and return it to the main circulation. Along the way, lymphatic fluid is filtered through small bean-shaped structures called lymph nodes, which trap debris such as bacteria, or escaped cancer cells. You may think of the lymphatic system as a network of sewer lines.

Most of the lymphatic fluid from the breast drains toward the armpit area (the axilla), where it is filtered through the axillary lymph nodes. By examining these nodes, the surgeon can get a good indication of whether cancer cells have begun to escape from the breast toward the rest of the body.

 

 

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How Breasts Change
From birth to old age, breasts go through more changes than almost any other organ in the body.

One to two years before menarche (first menstrual period) breasts begin to grow under the influence of the female hormones estrogen and progesterone.

During reproductive years, variations in the levels of these hormones cause the breasts to go through monthly cycles: milk glands become engorged and the breasts swell, as if getting ready for a pregnancy, then return to their inactive state again.

At menopause, levels of hormones drop, many milk producing glands shrink and disappear, and some of the breast tissue is replaced with fat.

All these changes sometimes damage the cells' DNA (the genetic material that
tells the cell how to divide and grow). This damage may lead to cancer.

 

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