Anatomy of the Human Breast

Picture showing CS of Breast

The female breast is composed of lobules of milk-producing glands surrounded by fatty tissue. Ducts run from these glands to outlets at the nipple. The breasts have no muscles but are held by ligaments. A major network of lymph vessels surrounds the breasts and drains into lymph nodes in the armpit area(axilla).

The normal female breast weighs between 50 - 500 grams. The shape and contour of the breast is mostly influenced by the woman's body type. Each breast consists of 15 to 20 sections, called lobes. Each lobe consists of smaller lobules that make up even smaller bulbs referred to as a terminal ductal lobular unit. This network of lobes, lobules and bulbs are all interconnected and end at the nipple. Surrounding the nipple is the slightly raised pigmented skin known as the areola, which contains sweat glands and sebaceous glands. Both the nipple and the surrounding areola contain smooth muscle fibers that are responsible for the erect nipple. The areola also contains Montgomery's glands (often appear as small raised bumps) which lubricate the region.



The breast is drained by lymph nodes to multiple areas that include the skin surrounding the breast, the chest wall, and the axilla (armpit). The majority of the lymphatic drainage is via the axilla region. This is why general surgeons use the lymph nodes in the axillary region to assess the spread of breast cancer when considering the appropriate therapy.



Picture: The anatomy of the breast includes the lactiferous, or milk ducts, and the mammary lobules.

The Microscopic Anatomy:

• The Lobules: The lobules, also called the lobular units, are responsible for the production of milk.
• The Ductal System: The milk is collected by distal lactiferous ducts or acini which merge into minor and then major lactiferous ducts. In most instances, these empty into the major duct or sinus which ends in the nipple. The ductal system has a ductal epithelium surrounded by a myo-epithelium. This ductal epithelium is responsible for the propulsion of milk through the ductal system as it has contractile capabilities. This ductal system is sealed and surrounded by an uninterrupted basement membrane.
• The Stroma: This interlobular tissue, also referred to as connective tissue, contains capillaries and other specialized cells.
• Cooper's Ligaments: These are dense strands of fascia found throughout the entire breast which end on the skin itself.
• The Basement Membrane of the Ductal System: It is essential to visualize the basement membrane in the microscopic analysis of a malignant breast tumor. This will assist in the assessment as to whether a tumor is "in situ" (has not grown through the basement membrane) or "invasive" (has grown through the basement membrane).

Menstrual cycle, pregnancy, breast feeding, weight gain/loss, birth control, and changes in hormones can all contribute to temporary changes in the shape and contour of the breast tissue. Since the breast have no actual supportive muscular tissue within the breast there are no "exercises" that can firm or tone the breast. Younger women may be able to produce a slight lifting affect of the breast by toning the underlying pectoral muscles.