paired structure on the anterior thoracic wall, in the pectoral region. present in both males and females, yet are more prominent in females following puberty.

In females: contain mammary glands – a key accessory gland of the female reproductive system involved in lactation.

Surface anatomy

• anterior thoracic wall
  • extends horizontally from the lateral border of the sternum to the mid-axillary line.
  • Spans vertically, between the 2nd and 6th costal cartilages.
  • superficial to the pectoralis major and serratus anterior muscles.
• nipple
  • centre of breast, composed mostly of smooth muscle fibres.
  • Surrounding pigmented area of skin areolae.
    • contains sebaceous glands which enlarge during pregnancy, secreting an oily substance that acts as a protective lubricant for the nipple.

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.

Anatomical structure

Composed of mammary glands surrounded by a connective tissue stroma.

• Mammary Glands
  • modified sweat glands consisting of a series of ducts and secretory lobules (15-20).
  • lobule = many alveoli drained by a single lactiferous duct. These ducts converge at the nipple like spokes of a wheel.
• Connective Tissue Stroma
  • supporting structure surrounding mammary glands. Has a fibrous and a fatty component.
  • fibrous stroma condenses to form suspensory ligaments (of Cooper). These ligaments function to:
    • Attach and secure the breast to the dermis and underlying pectoral fascia.
    • Separate the secretory lobules of the breast.
• Pectoral Fascia
  • The base of the breast lies on the pectoral fascia which acts as an attachment point for the suspensory ligaments.
  • layer of loose connective tissue between the breast and pectoral fascia – known as the retromammary space. This is a potential space, often used in reconstructive plastic surgery.

Vasculature

Arterial supply to the medial aspect of the breast is via the internal thoracic artery (also known as internal mammary artery) – a branch of the subclavian artery.

The lateral part of the breast receives blood from four vessels:

• Lateral thoracic and thoracoacromial branches – originate from the axillary artery.
• Lateral mammary branches – originate from the posterior intercostal arteries (derived from the aorta). They supply the lateral aspect of the breast in the 2nd, 3rd and 4th intercostal spaces.