Nipple

The nipple is a raised region of tissue on the surface of the breast from which, in lactating females, milk from the mammary gland leaves the body through the lactiferous ducts to nurse an infant. The milk can flow through the nipple passively, or it can be ejected by smooth muscle contractions that occur along with the ductal system. The nipple is surrounded by the areola, which is often a darker colour than the surrounding skin. When referring to non-humans, the female nipple is often called a teat. "Nipple" or "teat" can also be used to describe the flexible mouthpiece of a baby bottle. Male mammals also have nipples, but without the same level of function or prominence. In humans, the nipples of both females and males can be sexually stimulated as part of sexual arousal. In many cultures, female nipples are sexualized, or regarded as sex objects and evaluated in terms of their physical characteristics and sex appeal. As such, there are often mores for their coverage.