Anatomy

• In females, the breasts contain the mammary glands – an accessory gland of the female reproductive system. The mammary glands are the key structures involved in lactation.
• Surface anatomy:

  • Extends horizontally from the lateral border of the sternum to the mid-axillary line
  • Vertically spans the 2nd to 6th costal cartilages
  • Lies superficially to the pectoralis major and serratus anterior muscles
• The breast can be considered to be composed of two regions:

  • Circular body – largest and most prominent part of the breast.
  • Axillary tail – smaller part, runs along the inferior lateral edge of the pectoralis major towards the axillary fossa.
• The breast is composed of mammary glands surrounded by a connective tissue stroma.
• Mammary glands:

  • Modified sweat glands
  • Consist of a series of ducts and secretory lobules
  • Each lobule consists of many alveoli drained by a single lactiferous duct
  • These ducts converge at the nipple
• Vasculature:

  • Arterial supply to the medial aspect of the breast is via the internal thoracic artery - a branch of the subclavian artery
  • The lateral breast receives blood from four vessels - originate from the axillary and intercostal arteries
• There are three groups of lymph nodes that receive lymph from breast tissue:

  • Axillary nodes - 75%
  • Parasternal nodes - 20%
  • Posterior intercostal nodes - 5%
• There are 5 groups of axillary lymph nodes, they all drain into the apical nodes:

  • Pectoral
  • Posterior
  • Central
  • Lateral
  • Apical
• Venous drainage of the breast is into the axillary and internal thoracic veins
• Lymphatic drainage:

  • Most of breast and lateral - anterior 'pectoral' nodes and then to the axillary lymph nodes
  • Medial quadrants - parasternal lymph nodes or opposite breast
  • Inferior quadrants- deep abdominal lymph nodes
• Lymph from the axillary nodes drains into the clavicular nodes and then the subclavian lymphatic trunk
• Lymph from the parasternal nodes drains into the bronchomediastinal lymphatic trunk and into the systemic circulation