Nipple

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In its most general form, a nipple is a structure from which a fluid emanates. More specifically, it is the projection on the breasts or udder of a mammal by which breast milk is delivered to a mother's young. In this sense, it is often called a teat, especially when referring to non-humans. The rubber mouthpiece of a baby bottle or pacifier may also be referred to as a "nipple" or a "teat".

Contents

Etymology

The word "teat" is of Germanic origin, having the same origin as the Dutch word "tiet" and German "Zitze". In turn, this word has Indo-European roots, as may be seen in the Welsh word "teth". The Old English for teat was "tit", which is still used as a vulgar or slang term for "breast" in Modern English.

Anatomy

In the anatomy of mammals, a nipple or mammary papilla or teat is a small projection of skin containing the outlets for 15-20 lactiferous ducts arranged cylindrically around the tip. The skin of the nipple is rich in a supply of special nerves that are sensitive to certain stimuli. The physiological purpose of nipples is to deliver milk to the infant, produced in the female mammary glands during lactation.

Marsupials and eutherian mammals typically have an even number of nipples arranged bilaterally, from as few as two to as many as 20.[1] They develop in the embryo, along the 'milk lines'. Most mammals develop multiple nipples along each milk line, with the total number approximating the maximum litter size, and half the total number (i.e. the number on one side) approximating the average litter size for that species. Monotremes, such as the platypus, lack teats; their young drink milk directly from pores in the skin (similar to sweat glands), or by sucking it off of hairs surrounding the pores.

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