breast (anatomy)

Last reviewed 01/2018

The breasts are paired structures situated on the anterior thorax. They sit superficial to the pectoral muscles usually within the boundaries of ribs 3 to 7 and the parasternal and anterior axillary lines. The mammary glands are located within the breasts and they are accessory female reproductive organs which produce milk at the end of pregnancy. Although both genders have breasts, usually the mammary glands are only rudimentary in males. Although varying in position with age, the nipple typically resides at the level of the fourth intercostal space just lateral to the mid-clavicular line. Another landmark for this level is about 2-3 cm below the level of the mid-humerus.

The areola is an area of pigmented skin around the nipple that contains lots of sebaceous areolar glands. The superior and lateral part of the mammary gland ascends into the axilla as the 'axillary tail'. Supportive ligaments pass from the deep fascia over pectoralis major and serratus anterior, through the breast to the deep surface of the skin. These are called suspensory ligaments of Cooper.

The blood supply of the breast derives from perforating vessels from several sources:

• internal mammary artery (60%)
• lateral thoracic artery (30%)
• intercostal arteries
• axillary artery
• thoracodorsal artery
• subscapular artery
• pectoral arteries

Lymphatic drainage from the breast is described in the submenu, but key basins include:

• axillary nodes
• internal mammary nodes
• subdiaphragmatic nodes
• intra-abdominal nodes

The innervation of the breast is from the branches of the first to seventh intercostal nerves.