Normal nipples are cylindrical protrusions with holes, with a diameter of about 1 cm and a height of about 1.5-2 cm, and are dark. Nipple, also called nipple, is a cylindrical part protruding from the center of mammalian breast, which is harder than areola and breast. Human female nipple is an important sexual sensitive area, which has the function of breastfeeding.

The nipple is composed of tight smooth muscle and connective tissue. Smooth muscles are arranged in a ring or radial pattern. When encountering sexual or mechanical stimulation, smooth muscle contracts, which can make the nipple hard and convex. The breasts of adult women are hemispherical, the nipples are cylindrical, the skin in the central part is reddish, and the sebaceous glands are called areola. The breast is mainly composed of 15~20 glands (mammary glands), lobules and adipose tissue.

Extended data

Development process: before puberty, girls' nipples will bulge separately. Since then, nipples and breasts have raised a hill. With the further enlargement of the breast, the nipple and areola protrude and the breast contour increases. When nipples reach maturity, most people's nipples are protruding outward.

Unmarried women and infertile women have smaller nipples. Only after pregnancy, the breasts and nipples are affected by estrogen and progesterone of pregnant women, mammary vesicles and mammary ducts proliferate, and nipples gradually increase and become more prominent, preparing for feeding children.

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