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Anatomy of the Breast
Breast quadrants. From Bates B: A guide to physical examination
and history taking, ed 6, Philadelphia, 1995, Lippincott-Raven. |
The female breast is suspended from the chest
wall between the 2nd and 6th ribs. The breast is bounded medially
by the lateral edge of the sternum and extends laterally to
the anterior axillary line. Breast tissue can be divided into
four quadrants and is roughly circular except at the upper outer
quadrant where the tail of Spence extends into the axilla. The
breast is composed of three types of tissue:
- Glandular tissue
- Fibrous tissue
- Fat
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| Three types of breast tissue. From Bates
B: A guide to physical examination and history taking,
ed 6, Philadelphia, 1995, Lippincott-Raven. |
Glandular tissue produces milk and is made up of lobes arranged
radially around the nipple that each drain into a duct. Each duct
opens onto the nipple surface. This glandular tissue is supported
by fibrous tissue that tethers the breast to the skin and to the
underlying fascia. Fatty tissue surrounds the breast. The proportion
of fat present in breast tissue varies by age, pregnancy, and other
factors.
The nipple—areola complex contains
smooth muscle fibers arranged longitudinally and circularly
in the nipple and in concentric rings in the areola. These smooth
muscle fibers function to contract the areola and compress the
nipple, thereby emptying the milk ducts.
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Lymphatic network. From Bates B: A guide to physical
examination and history taking, ed 6, Philadelphia,
1995, Lippincott-Raven.
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Lymphatic drainage of the breast. From Swartz MH: Textbook
of physical diagnosis: history and examination., ed
3, Philadelphia, 1998, Saunders.
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A rich lymphatic network of vessels in the
breast drains mainly into the axillary and internal mammary
lymph nodes. The axillary nodes are the more numerous. The central
nodes deep within the axilla are the most often palpable. There
are also pectoral, subscapular, and lateral axillary nodes that
are usually not palpable. Lymph from the lower outer quadrant
drains to the lateral and inferior axillary nodes, while lymph
from the areola, upper outer quadrants, and tail drains into
the lymph nodes in the superior part of the axilla. Most of
the lymph from the inner quadrants drains into the internal
mammary lymph nodes even though these are much fewer in number
(Bland).
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