There is a good supply of blood vessels and nerves in the nipples. Arteries tend to supply oxygen rich blood from the heart to breasts and veins carry away de-oxygenated blood back to the heart.
The arteries that supply the blood to the breasts are the internal thoracic artery, the lateral thoracic artery, the thoracoacromial artery, and the posterior intercostal arteries. The axillary vein is mainly responsible for taking the blood away from the breast and some to the internal thoracic vein and the intercostal veins.
Blood is drained away from the breasts by veins leading to a large vein called the superior vena cava which enters the right side of the heart.