nipple
Meaning of nipple: The raised opening at the center of the breast where the milk ducts reach the surface, ringed by darker skin.
Definition of nipple
The nipple is the small raised structure at the center of the breast through which milk leaves the body. Several milk ducts open at its tip, each draining one section of the gland. It sits within the areola, a ring of darker skin holding small glands that lubricate the surface, and it contains smooth muscle that makes it firm in response to cold or touch.
What is it made of?
Under the surface are the ends of the milk ducts, bundles of smooth muscle arranged in rings and lines, and one of the densest nerve supplies on the body. There is no fat inside it. The muscle contracts on cold, touch or feeding, which stiffens the tip and helps milk move. The surrounding areola carries small raised bumps, oil glands whose secretion protects the skin during feeding. Color deepens during pregnancy and generally stays darker afterward. Shape varies widely between people, and a tip that has always sat flat or turned inward is a normal variant found in a substantial minority.
What happens during breastfeeding?
Suckling stimulates the nerve endings, and the signal travels to the brain. Two hormones answer. One drives milk production in the gland, and the other squeezes the muscle cells around the milk sacs so milk is pushed down the ducts, felt as the let-down. The infant needs a wide mouthful of breast tissue rather than the tip alone, and pain or cracking usually reflects how the baby is attached rather than any fault in the nipple itself.
Which changes are examined?
| Change | What it may indicate |
|---|---|
| New pulling inward in an adult | Tethering by an underlying process, and it is assessed promptly |
| Persistent scaly, itchy rash on the tip | Eczema, or Paget disease of the breast, which looks similar |
| Fluid from one duct, clear or bloodstained | Investigated further, as covered under nipple discharge |
| Milky fluid from both, unrelated to feeding | Usually a hormonal cause rather than a breast one |
| Lifelong inward position | A common normal variation |
Also known as
Used in a sentence
Examination noted no nipple retraction, skin change or discharge.
Good to know
A nipple that has always turned inward is a common normal variation, while one that newly pulls inward in an adult, or develops a persistent scaly rash, is a change that prompts examination.