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.Each lactiferous duct has a dilated portion deep to the areola called the lactiferous sinus in which there’s a small drop of milk that accumulates or remains in a nursing mother, which becomes expelled from the areola when compressed during feeding.Next, the stroma of the breast is composed of adipose tissue and fibrous connective tissue.In a non-lactating state, the adipose tissue is situated between the lobes and makes up most of the breast volume.The fibrous connective tissue of the stroma goes on to form fibrous condensations, called the suspensory ligaments of Cooper, which firmly attach the mammary glands to the dermis of the overlying skin.These fibrous connective tissue attachments help support the lobes and lobules of the mammary glands.Moving on, the areolae surround the nipples, which are typically located around the 4th intercostal space lateral to the mid clavicular line; but this varies depending on the size of the breast.Each areola contains a large number of sebaceous glands, which get bigger during pregnancy and secrete an oily substance that acts as a lubricant for the areola and nipple.The nipples are conical or cylindrical prominences in the centers of the areola.Keep in mind that nipples have no fat, hair, or sweat glands.The lactiferous ducts open into the tips of the nipples.Structurally, the nipples are composed of circularly arranged smooth muscle fibers that compress the lactiferous ducts to help express milk during lactation.Now let’s look at the arterial supply of the breast, which derives from several arteries: the medial mammary branches, the lateral thoracic artery, the thoracoacromial arteries and posterior intercostal arteries.The medial mammary branches come from the internal thoracic artery which originates from the subclavian artery.The lateral thoracic and thoraco-acromial arteries are branches of the axillary artery.The posterior intercostal arteries are branches of the thoracic aorta in the 2nd, 3rd, and 4th intercostal spaces.Finally, the veins of the breast mainly drain into the axillary vein, but some also drain to the internal thoracic vein .Let’s move on to the lymphatic drainage of the breast.Basically, lymph passes from the nipple, areola and glandular lobules to the subareolar lymphatic plexus.From here, most lymph,especially from the lateral breast quadrants, initially drains to the anterior or pectoral nodes and then to the axillary lymph nodes.Sometimes, some lymph may drain directly to other axillary nodes or even to interpectoral, deltopectoral, supraclavicular or inferior deep cervical nodes.The remaining lymph, especially from the medial breast quadrants, drains to the parasternal lymph nodes or to the opposite breast.Lymph from the inferior quadrants may pass deeply to abdominal lymph nodes, specifically to the subdiaphragmatic inferior phrenic lymph nodes.Lymph from the skin of the breast, with the exception of the nipple and areola, drains into the ipsilateral axillary, inferior deep cervical, and infraclavicular lymph nodes and also into the parasternal lymph nodes of both sides.Lymph from the axillary nodes first drains into the clavicular lymph nodes and then into the subclavian lymphatic trunk.And finally, lymph from the parasternal nodes enters the bronchomediastinal lymphatic trunks which goes on to eventually drain into the venous circulation.Finally, the nerves of the breast come from anterior and lateral cutaneous branches of the 4th through 6th intercostal nerves.The branches of the intercostal nerves go through the pectoral fascia covering the pectoralis major in order to reach the overlying subcutaneous tissue and skin of the breast.The branches of the intercostal nerves carry sensory fibers from the skin of the breast and sympathetic fibers to the blood vessels in the breasts and smooth muscle in the skin and nipple.All right, as a quick recap.The breasts extend transversally from the lateral border of the sternum to the midaxillary line and vertically from the 2nd through the 6th ribs.A small part of the breast might extend along the inferolateral edge of the pectoralis major, forming the tail of Spence.The retromammary space is between the breast and the pectoral fascia, and allows movement of the breast to the structures deep to it.The mammary glands are made up of 120 to 2012 lobes, each of them containing several small lobules, which further contain clusters of alveoli that have mammary secretory epithelial cells.The alveoli, lobules and lobes are connected to ducts that join to form larger ducts called lactiferous ducts, which drain the mammary glands through lactiferous sinuses to the tip of the nipple..The nipples are conical or cylindrical prominences in the centers of the areola and have no fat, hair, or sweat glands.The areola are pigmented areas of skin surrounding the nipple.The stroma of the breast is composed of adipose tissue and fibrous connective tissue which make up the bulk of the breast tissue and support the mammary glands respectively.Arteries of the breast include the medial mammary branches, the lateral thoracic artery, the thoraco-acromial arteries and posterior intercostal arteries.The venous drainage is mainly to the axillary vein, but there is some drainage to the internal thoracic vein.Lymph from the lateral breast quadrants drains to the axillary lymph nodes, initially to the anterior or pectoral nodes.The remaining lymph, especially from the medial breast quadrants, drains to the parasternal lymph nodes or to the opposite breasts.Lymph from the inferior quadrants may pass deeply to abdominal lymph nodes.Lymph from the skin of the breast, with the exception of the nipple and areola, drains into the ipsilateral axillary, inferior deep cervical, and infraclavicular lymph nodes and also into the parasternal lymph nodes of both sides.The nerves innervating the breast come from anterior and lateral cutaneous branches of the 4th through 6th