The Breast
The female breast varies enormously in size and shape. Since it consists mostly of a fat pad, its shape will change according to the body's position and the pull of gravity. It is thus important to understand the breast's attachment to the torso.
The upper extent of the breast is about halfway up the pectoralis muscle. The circle of the breast is cut by the lateral portion of pectoralis, sending a small portion into the armpit; this part of the breast is called the axillary tail. The medial extent is the lateral border of the sternum. The lower extent is the the sixth rib, below the level of the sternum, over the very top of external oblique. These attachments hold true regardless of the size or position of the breast.
The nipple is surrounded by a colored portion called the areola (uh-REE-oh-luh) which varies greatly in diameter. It may overlie a mass of its own that sits on the greater hemisphere of the breast.
In an upright figure, nipples can be seen to diverge laterally; they should not, in any case, be drawn to point straight forward. The hang of the breast in an upright figure flattens its top curve and fills its lower curve.
The fat pad under the male breast is slight, leaving the nipple to lie close to the pectoralis muscle near the lower lateral border. On a muscular pectoralis, the nipple is moved away from this border slightly medially.