What is the nipple?
The nipple (mammilla) rises in the center of the circular, dark-toned areola that forms the center of the breast. The 12 to 15 milk ducts, which widen under the nipple and areola to form milk sacs and then rise vertically in the nipple, open outward in the coves of the nipple tip.
There are smooth muscle cells in both the nipple and areola that contract in response to mechanical stimulation (such as from the infant’s mouth): This causes the nipple to erect, giving it a more or less wrinkled appearance depending on the contraction of the muscles. This erection makes the nipple easier for the infant to grasp during sucking. In response to the mechanical stimulation of the nipple during breastfeeding, the hypothalamus in the brain secretes the two hormones oxytocin and prolactin:
Oxytocin causes the milk ducts to contract, causing milk to leak from the nipple. It also promotes contractions of the uterus, which are important for involution after childbirth. Prolactin stimulates milk production.
Nipple shapes
Nipples: color, sebaceous and scent glands.
The areola and nipple in girls and young women are usually pale pink to brownish in color. Under the influence of pregnancy they become darker, because the pigmentation increases.
The areola is surrounded by circularly arranged bumps. These are small sebaceous glands (Montgomery glands) whose secretion moisturizes the skin of the areola.
What is the function of the nipple?
The nipple’s primary function is to allow the newborn and infant to suckle and thus feed.
What problems can the nipple cause?
Flat or inverted nipples are usually congenital and harmless. However, they must be distinguished from a disease-related retraction of the nipple, which usually only occurs on one side. The cause of the latter is usually a tumor.
The nipple may be completely absent (athelie), usually associated with the absence of the entire breast in question (amastia).
Nipple inflammation (thelitis) may occur during breastfeeding or in the puerperium. Fissures or rhagades of the nipple are also usually due to pregnancy or the puerperium.
Benign and malignant neoplasms (growths, tumors) can develop in the nipple area.
Some women also have an additional “whole” breast along the milk line (usually under the armpit). Doctors refer to this as polymastia. The excess breast (including nipple and areola) can be removed completely by surgery.
