Anatomy of the Breast

Anatomy of the Breast

• The breast, as mammary glands, is for feeding infants with breast milk during lactation.
• The round shape of the breast limits the loss of maternal body heat.
• Milk production depends on a higher temperature for the mammary gland tissues (lactiferous ducts).
• The breast is located on the anterior thoracic wall.
• It extends horizontally from the lateral border of the sternum to the mid-axillary line.
• Vertically, it spans between the 2nd and 6th intercostal cartilages.
• It lies superficially to the Pectoralis Major (PM) and Serratus Anterior muscles.

Regions of the Breast

• The breast has two main regions:
  • Circular body: The largest and most prominent part of the breast.
  • Axillary tail: A smaller part along the inferior lateral edge of the Pectoralis Major muscle, towards the axillary fossa.

Parts of the Breast

• The nipple is centrally located, composed of smooth muscle fibers.
• The areola surrounds the nipple, and is a pigmented area of skin.
• Numerous sebaceous glands in the areola enlarge during pregnancy, secreting an oily substance that lubricates the nipple.

Composition of the Breast

• The breast is composed of mammary glands surrounded by a connective tissue stroma.
• Mammary glands are modified sweat glands.
• They consist of ducts and secretory lobules (15-20).
• Each lobule has many alveoli drained by a single lactiferous duct.
• These ducts converge at the nipple.

Connective Tissue Stroma

• The connective tissue stroma supports the mammary glands.
• It has fibrous and fatty components.
• The fibrous stroma forms suspensory ligaments (of Cooper).
• These ligaments attach and secure the breast to the dermis and underlying pectoral fascia.
• They also separate secretory lobules of the breast.

Lymphatic Drainage

• Breast lymphatic drainage is clinically important due to its role in breast cancer metastasis.
• Three groups of lymph nodes receive lymph from breast tissue:
  • Axillary nodes (75%)
  • Parasternal nodes (20%)
  • Posterior intercostal nodes (5%)
• The skin of the breast drains to axillary, inferior deep cervical, and infraclavicular nodes.
• The nipple and areola drain to the subareolar lymphatic plexus.

Disposition of Axillary Lymph Nodes

• Axillary lymph nodes include pectoral, subscapular, and humeral groups. These drain to the central and apical axillary nodes.

Importance of Lymphatic Drainage of the Breast

• Approximately 75% of breast lymph travels to the axillary lymph nodes, on the same side of the body.
• 25% travels to the parasternal nodes (beside the sternum).
• A small amount travels to the other breast and abdominal lymph nodes.

The Axillary Lymph Nodes (ALN)

• ALNs consist of pectoral, subscapular, and humeral groups.
• These drain to the central and apical axillary lymph nodes.

Nerve Supply

• The breast is innervated by the anterior and lateral cutaneous branches of the 4th to 6th intercostal nerves.
• These nerves contain sensory and autonomic nerve fibers that regulate smooth muscle and blood vessel tone.
• Nerve function doesn't control milk secretion.
• Milk secretion is controlled by prolactin, secreted from the anterior pituitary gland.

Clinical Significance

• Common benign conditions include puerperal mastitis and fibrocystic breast changes/mastalgia.
• Lactation unrelated to pregnancy can occur (galactorrhea) due to drugs, stress, or endocrine disorders.
• Newborn infants can produce milk due to the mother's circulating hormones (prolactin, oxytocin, etc.).
• Breast cancer is a common cause of cancer death in women.
• Breast cancer risk can be decreased by regular breast exams, mammograms, self-exams, healthy diet, and exercise.

Explore the fascinating structure and function of the breast in this quiz. Learn about its anatomy, regions, and parts, including the importance of lactation and temperature regulation. Test your understanding of the breast as a critical component of the mammary system.