Nipple

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Nipple

In its most general form, a nipple is a structure

Structure

Structure is a fundamental and sometimes intangible notion covering the recognition, observation, nature , and stability of patterns and relationships of entities....
from which a fluid emanates. More specifically, it is the projection on the breasts of a mammal by which breast milk

Breast milk

Breast milk refers to the milk produced by a mother to feed her baby. It provides the primary source of nutrition for newborns before they are able to eat and digest other foods; older infants and toddlers may continue to be breastfeeding....
is delivered to a mother's young.

he anatomy

Anatomy

Anatomy is a branch of biology that is the consideration of the body plan. It is a general term that includes human anatomy, animal anatomy and plant anatomy ....
of mammal

Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
s, a nipple
Nipple

In its most general form, a nipple is a structure from which a fluid emanates. More specifically, it is the projection on the breasts of a mammal by which breast milk is delivered to a mother's young....
or mammary papilla is a small projection of skin

Skin

The skin is the outer covering of the body, also known as the epidermis. It is the largest organ of the integumentary system made up of multiple layers of epithelial biological tissue, and guards the underlying muscles, bones, ligaments and organ s....
containing the outlets for 15-20 lactiferous duct

Lactiferous duct

Lactiferous ducts lead from the lobules of the mammary gland to the tip of the nipple. They are also referred to as galactophores, galactophorous ducts, mammary ducts, mamillary ducts and milk ducts....
s arranged cylindrically around the tip.

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Encyclopedia

In its most general form, a nipple is a structure

Structure

Breast milk

Anatomy

In the anatomy

Anatomy

Anatomy is a branch of biology that is the consideration of the body plan. It is a general term that includes human anatomy, animal anatomy and plant anatomy ....
of mammal

Mammal

Skin

Lactiferous duct

Nerve

A nerve is an enclosed, cable-like bundle of Peripheral nervous system axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons....
s that are sensitive to certain stimuli. The physiological purpose of nipples is to deliver milk

Milk

Milk is an opaque white liquid produced by the mammary glands of female mammals . It provides the primary source of nutrition for newborn mammals before they are able to digestion other types of food....
to the infant, produced in the female mammary gland

Mammary gland

Mammary glands are the organ s that, in mammals, produce milk for the sustenance of the young. These exocrine glands are enlarged and modified sweat glands and give mammals their name....
s during lactation

Lactation

Lactation describes the secretion of milk from the mammary glands, the process of providing that milk to the young, and the period of time that a mother lactates to feed her young....
. In the male

Malé

Mal? , population 104,403 , is the Capital , the largest city in terms of population, and the name of an island in the Maldives. It is located at the southern edge of North Male' Atoll Kaafu Atoll....
, nipples are often not considered functional with regard to breastfeeding

Breastfeeding

Breastfeeding is the feeding of an infant or young child with breast milk directly from human breasts rather than from a baby bottle or other container....
, although male lactation

Male lactation

The phenomenon of male lactation in humans has become more common in recent years due to the use of medications that stimulate a man's mammary glands....
is possible. Mammalian infants have a rooting instinct (moving their head so as to bring their mouth towards whatever is touching their face) for seeking the nipple, and a suck
Suction

Suction is the flow of a fluid into a partial vacuum, or region of low pressure. The pressure gradient force between this region and the ambient pressure will propel matter toward the low pressure area....
ing instinct for extracting milk.

Mammals typically have an even number of nipples arranged around bilaterally. They develop in the embryo

Embryo

An embryo is a multicellular organism ploidy eukaryote in its earliest stage of development, from the time of first cell division until birth, Egg , or germination....
, along the 'milk line

Milk line

The milk lines are two parallel lines, formed by thickenings of the epidermis along the ventral surface of mammals of both sexes. They extend from the upper limbs to the lower limbs and are developed in the embryo....
s'. 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. In the primitive mammals (monotreme

Monotreme

Monotremes are mammals that lay eggs instead of giving birth to live young like Marsupialias and Placentalia .They are conventionally treated as comprising a single order Monotremata, though a recent classification proposes to divide them into the orders Platypoda and Tachyglossa ....
s such as the platypus

Platypus

The Platypus is a semi-aquatic mammal Endemic to Eastern states of Australia, including Tasmania. Together with the four species of echidna, it is one of the five extant species of monotremes, the only mammals that lay Egg instead of giving birth to live young....
), the mammary glands empty onto the skin without a nipple. In cetaceans such as whales, the infant cannot form a suction-seal to nurse, due to its mouth structure. Therefore the whale's nipple is unlike that of any other mammal. Rather than requiring a sucking action, the discharge of milk is powered by maternal muscles. The calf takes the extended nipple into its mouth, and the mother ejects or expels her milk into the mouth of the calf.

Most human

Human

A human being, also human or man, is a member of a species of bipedalism primates in the family Hominidae . Mitochondrial DNA evidence indicates that modern humans originated in east Africa about 200,000 years ago....
s have two nipples after birth, located near the center of each breast

Breast

The breast is the upper ventral region of an animal?s torso, particularly that of mammals, including human beings. The breasts of a female primate?s body contain the mammary glands, which secrete milk used to feed infants....
and surrounded by an area of sensitive, pigmented skin known as the areola

Areola

In human anatomy, the term areola, plural areolae, is used to describe any circular area such as the colored skin surrounding the nipple....
. Human fetuses develop several more nipples along the milk lines, which extend from the axilla (armpit), along the abdominal muscles, down to the pubis

Pubis

Pubis may refer to:* Pubis * Mons pubis, a padding of fat that protects the pubis bone...
(groin) on both sides. Those nipples usually disappear before birth, but sometimes remain, resulting in supernumerary nipple

Supernumerary nipple

A supernumerary nipple is an supernumerary body part nipple occurring in mammals, including humans. Often mistaken for mole , supernumerary nipples are diagnosed at a rate of 1 in 18 humans....
s which occasionally have lactiferous glands attached, but usually do not.

The pigments of the nipple and areola are brown eumelanin (a brown pigment) and to a greater extent pheomelanin (a red pigment). Exposure to cold temperatures and breastfeeding

Breastfeeding

Breastfeeding is the feeding of an infant or young child with breast milk directly from human breasts rather than from a baby bottle or other container....
are primary causes for the nipples to become erect; nipple erections are a product of the pilomotor reflex which causes goose bumps

Goose bumps

Goose bumps, also called goose flesh, goose pimples, chill bumps, or the medical term cutis anserina, are the bumps on a person's skin at the base of body hairs which may involuntarily develop when a person is cold or experiences strong emotions such as fear or awe....
. Sexual arousal

Sexual arousal

Sexual arousal is the the arousal of sexual desires in preparation for sexual behavior....
may also cause the nipples to become erect. The nipple and areola of males and females can be erotic receptors, sometimes intense enough to elicit orgasm

Orgasm

An orgasm is the conclusion of the Human sexual response cycle#Plateau phase of Human sexual response cycle, and may be experienced by both males and females....
in some individuals of either sex. They are not, however, sex organs because since mammals of both sexes all have nipples, nipples don't possess the defining quality of a sex organ of differentiating the sex of any animal.

The average projection and size of human female nipples is slightly more than 3/8 inches (10mm).. Pregnancy and nursing tend to increase nipple size, sometimes permanently. Pregnancy also increases the pigmentation. The erection of the nipple is partially due to the cylindrically arranged muscle cells found within it. In many women, there are small bulges on the areola, which are called 'Montgomery bodies

Glands of Montgomery

Glands of Montgomery are sebaceous glands in the areola . The glands makes oily secretions to keep the areola and the nipple lubricated and protected....
'.

Sometimes, babies (male or female) are born producing milk. This is called 'witch's milk

Witch's milk

Witch's milk or neonatal milk is milk secreted from the breasts of some newborn infants. It is the result of influence by the mother's hormones before birth....
'; it is caused by maternal estrogen

Estrogen

Estrogens are a group of steroid compounds, named for their importance in the estrous cycle, and functioning as the primary female sex hormone....
s acting on the baby and is quite common. Witch's milk disappears after several days.

Nipples on male mammals

From conception until sexual differentiation

Sexual differentiation

Sexual differentiation is the process of development of the differences between males and females from an undifferentiated zygote . As male and female individuals develop from zygotes into fetuses, into infants, children, adolescents, and eventually into adults, sex and gender differences at many levels develop: genes, chromosomes, gonads, ho...
, all mammalian fetus

Fetus

A fetus is a developing mammal or other viviparous vertebrate, after the embryonic stage and before childbirth. The plural is fetuses, or sometimes feti....
es within the same species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring....
look the same, regardless of sex. In humans this lasts for around 14 weeks after which, genetically-male fetuses begin producing male hormone

Hormone

Hormones are chemicals released by cells that affect cells in other parts of the body. Only a small amount of hormone is required to alter cell metabolism....
s such as testosterone

Testosterone

Testosterone is a steroid hormone from the androgen group. In mammals, testosterone is primarily secreted in the testis of males and the ovaries of females, although small amounts are also secreted by the adrenal glands....
. Usually, males' nipples do not change much past this point. However, some males develop a condition known as gynecomastia

Gynecomastia

Gynecomastia, or gynaecomastia, is the development of abnormally large mammary glands in males resulting in breast enlargement, which can sometimes cause secretion of milk....
, in which the fatty tissue around and under the nipple develops into something similar to a female breast. This may happen whenever the testosterone level drops.

Nipple

Anatomy

Nipples on male mammals

See also