Breasts: Anatomy and Function

• Mammary glands in the pectoral region make up the breasts.
• Both males and females have breasts, but females' breasts get bigger after puberty.
• A female breast's primary job is to make milk (lactation) so that a newborn can be fed.

Location and Extent

• Breasts extend from the 2nd to the 6th or 7th rib vertically.
• Breasts reach from the lateral edge of the sternum to the mid-axillary line horizontally.
• About 2/3 of the breast is over the pectoralis major muscle.
• The serratus anterior muscle is covered by the remaining third.

Structure

• The breast is made up of glandular, connective, and adipose tissue
• There are 15–20 lobes in the glandular tissue, each of which is drained by a lactiferous duct.
• The lactiferous ducts meet at the nipple.
• Each duct widens into a lactiferous sinus just before it reaches the nipple.
• During lactation, milk is stored in the lactiferous sinuses.
• The connective tissue creates suspensory ligaments, also known as Cooper's ligaments, that hold the breast in place and attach it to the skin and pectoral fascia.
• Adipose tissue fills the spaces between the lobes and surrounds them, which affects the size and shape of the breast.

Nipple and Areola

• Near the center of the breast is a conical projection called the nipple.
• Lactiferous duct openings can be found there.
• The areola is a circular area of pigmented skin around the nipple.
• It has sebaceous glands (Montgomery glands) that release an oily substance to keep the nipple and areola safe while nursing.

Vasculature

• Arterial supply to the breast:
  • Medial mammary branches branch off of the internal thoracic artery (internal mammary artery).
  • The lateral thoracic artery is in charge of the breast's lateral side.
  • The superior aspect is supplied by the thoracoacromial artery.
  • Small posterior intercostal artery branches.
• Venous drainage of the breast:
  • Arteries are followed.
  • Drains into the internal thoracic, axillary, and intercostal veins.

Lymphatic Drainage

• The lymphatic drainage of the breast is important in the clinic because it helps breast cancer spread.
• The majority of the lymph (75%) goes to the axillary lymph nodes, specifically:
  • Pectoral (anterior) nodes
  • Lateral nodes
  • Central nodes
  • Apical nodes
• Along the internal thoracic artery, lymph from the medial breast quadrants drains into the parasternal lymph nodes.
• Some lymph may also flow to the lymph nodes below the diaphragm or to those in the other breast.

Innervation

• The breast is supplied by:
  • Branches of the 4th to 6th intercostal nerves that are located on the front and sides of the body.
• The breast's skin, especially the nipple and areola, is sensed by these nerves.
• Because there are so many nerve endings in the nipple, it is very sensitive.
• The smooth muscle in the walls of the blood vessels and areola is innervated by the sympathetic nervous system.

Development

• Starting in the womb, the breasts start to grow (mammogenesis).
• Estrogen causes the mammary glands to grow and fat to be deposited during puberty, which makes the breasts bigger.
• During pregnancy, the mammary glands continue to grow and change to get ready for lactation.
• After menopause, estrogen levels go down, which causes the mammary glands to shrink and the breasts to get smaller.

Clinical Significance

• Breast cancer is a common disease in women.
• Finding problems early by doing self-exams, getting checked out by a doctor, and getting mammograms is very important for improving results.
• Mastitis is a breast infection that is often brought on by germs getting into the breast while it is lactating.
• Fibrocystic changes are common, non-cancerous diseases that cause breasts to feel painful or lumpy.
• Gynecomastia is the enlargement of the male breast, which can be brought on by hormone imbalances, drugs, or other medical conditions.