The breasts are the most prominent superficial structures in the anterior thoracic wall consisting of glandular tissue and a supporting fibrous and fatty matrix.

This glandular tissue, or mammary glands, are found in the subcutaneous tissue overlying the pectoralis major and minor muscles.

The amount of fat surrounding this glandular tissue will determine the size of the breasts.

Breasts have a circular body and a nipple in the center, surrounded by a pigmented area of skin called the areola.

Each breast has the following boundaries: transversally from the lateral border of the sternum to the midaxillary line and vertically from the second through the sixth ribs.

Two thirds of the underlying tissue of the breast is formed by the pectoral fascia covering the pectoralis major and the other third is formed by the fascia that covers the serratus anterior muscle.

A small part of the breast might extend along the inferolateral edge of the pectoralis major, going towards the axillary fossa or the armpit.

Here it forms an axillary process or tail, called the tail of Spence.

Now, let’s take a look at this sagittal section of the female breast.

As you can see, there’s a fine space between the breast and the pectoral fascia.

This is called the retromammary space or bursa, which is a loose subcutaneous tissue plane.

This plane contains a small amount of fat which allows the breast to move a bit on the pectoral fascia.

Breasts contain the mammary glands responsible for lactation in females.

Mammary glands are made up of 12 to 20 lobes, each of them containing many smaller lobules.

These smaller lobules have grape-like clusters of alveoli that contain mammary secretory epithelial cells, the milk producing cells of lactation.

These alveoli, lobules and lobes are connected through a network of ducts called the lactiferous ducts, and eventually form a unique lactiferous duct for each lobe which opens independently to the areola to drain the milk produced during lactation.