Nipple

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Information about Nipple

This article is about the anatomical structure. For other uses, see nipple (disambiguation).

Human female nipple and areola. Nipple in erect state.

Human male torso with nipples

In its most general form, a nipple is an appurtenance from which a fluid emanates, in this instance breast milk, to nurture a mother's young.

Anatomy

In the anatomy of mammals, a nipple or mammary papilla 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. In the male, nipples are often not considered functional with regard to breastfeeding, although male lactation is possible. Mammalian infants have a rooting instinct for seeking the nipple, and a sucking instinct for extracting milk.

Mammals typically have an even number of nipples arranged around bilaterally. In the primitive mammals (monotremes such as the platypus), the mammary glands empty onto the skin without a nipple.

In human anatomy, the two nipples are located near the center of the breasts, surrounded by an area of sensitive, pigmented skin known as the areola. The pigments of the nipple and areola are brown eumelanin (a brown pigment) and to a greater extent pheomelanin (a red pigment). The nipple and areola of males and females can be erotic receptors, or considered sex organs. Stimulation or sexual arousal can cause the nipples to become erect, due to the release of the polypeptide neurotransmitter oxytocin. Breastfeeding or exposure to cold temperatures often has this effect as well.

The average projection and size of human female nipples is slightly more than 3/8 inches (0.4 in./10mm.) ^[1]. Pregnancy and nursing tend to increase nipple size somewhat, and this increase may remain permanently thereafter. Pregnancy also increases the pigmentation of the nipples. 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'.

Embryologically, nipples develop along the 'milk lines' which in humans extend from the axilla (armpit) down to the pubis (groin) on both sides. 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. Most people develop two nipples (one on each breast) but some have supernumerary nipples. Occasionally, these have lactiferous glands attached.

Sometimes, babies (male or female) are born producing milk. This, called 'witch's milk', is caused by maternal estrogens acting on the baby and is quite normal. Witch's milk disappears after several days.

Nipples on male mammals

Starting at conception and lasting until about 14 weeks, all mammalian fetuses within the same species look the same, regardless of gender. After 14 weeks, genetically-male fetuses begin producing male hormones such as testosterone. As "female" is the "developmental default" for mammals, by 14 weeks, the nipples have already formed.

Most of the time, males' nipples don't change much past this point. However, some males develop a condition known as gynecomastia, in which the fatty tissue around and under the nipple develops into something similar to a female breast. Males who develop gynecomastia during puberty is said the effects are temporary unless they are obese. This may happen whenever the testosterone level drops because of medications (like those that treat prostate cancer) and by natural hormonal changes associated with aging, obesity, or puberty.

References

1. ^ M. Hussain, L. Rynn, C. Riordan and P. J. Regan, Nipple-areola reconstruction: outcome assessment; European Journal of Plastic Surgery, Vol. 26, Num. 7, December, 2003

Stephen Jay Gould, "Male Nipples and Clitoral Ripples", in Adam's Navel and Other Essays, London: Penguin, 1995.

• • [ e] Female reproductive system
Ovaries/Oogenesis	Germinal epithelium • Tunica albuginea • cortex (Cumulus oophorus, Stroma) • Medulla
Follicles/Folliculogenesis	corpus (hemorrhagicum, luteum, albicans) • Theca folliculi (externa, interna) • Follicular antrum (Follicular fluid) • Corona radiata • Zona pellucida • Membrana granulosa (Granulosa cells)
Ligaments	Proper • Suspensory • Round • Broad (Mesovarium, Mesosalpinx, Mesometrium) • Cardinal
Fallopian tubes	Isthmus • Ampulla • Infundibulum • Fimbria
Uterus	cervix/neck (External orifice, Canal of the cervix, Internal orifice) • corpus/body (Cavity of the body, Fundus) • layers (Endometrium, Myometrium, Perimetrium)
Vulva	Mons pubis • Labium (Labial commissures, Frenulum labiorum pudendi, Labia majora, Cleft of venus, Labia minora, Vulval vestibule, interlabial sulci) • Clitoris (Clitoral hood , Clitoral glans, Frenulum clitoridis, Clitoral crura, Corpus cavernosa, Vestibular bulbs) • Vagina (Bartholin's glands, Bartholin's ducts, Skene's glands, Skene's ducts, Fossa of vestibule of vagina, Vaginal fornix, Hymen)
Breast	Mammary glands • Nipple • Areola • Lactiferous duct
Other	G-spot • Urethral sponge

Nipple may refer to:

The nipple, in human or mammalian anatomy.
The flexible nozzle on a Baby bottle simulating a human nipple.
A nipple (plumbing), which is a type of pipe fitting.
A spoke nipple, which binds each spoke to a bicycle wheel rim.

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For the decoration, see .

Appurtenances (from late Latin appertinentia, from appertinere, "to appertain") is a legal term for what belongs to and goes with something else, the accessories or things usually conjoined with the substantive
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Breast milk usually refers to the milk produced by a human female which is usually fed to infants by breastfeeding. It provides the primary source of nutrition for newborns before they are able to eat solid food and digest a wider variety of food.
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Anatomy (from the Greek ἀνατομία anatomia, from ἀνατέμνειν
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Mammalia
Linnaeus, 1758

Subclasses & Infraclasses

Subclass †Allotheria*
Subclass Prototheria
Subclass Theria

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Skin layers: epidermis, dermis, and subcutis, showing a hair follicle, sweat gland & sebaceous gland.]] In zootomy and dermatology, skin is the largest organ of the integumentary system made up of multiple layers of epithelial tissues that guard underlying muscles and organs.
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Lactiferous ducts are lobes of the mammary gland at the tip of the nipple. They are also referred to as galactophores, galactophorous ducts, mammary ducts, mamillary ducts and milk ducts.
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Milk is an opaque white liquid produced by the mammary glands of female mammals (including monotremes). Mammary glands are highly specialized sweat glands. The female ability to produce milk is one of the defining characteristics of mammals.
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Mammary glands are the organs that, in the female mammal, produce milk for the sustenance of the young. These exocrine glands are enlarged and modified sweat glands and are the characteristic of mammals which gave the class its name.
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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.
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Male (♂) refers to the sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilisation.
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Breastfeeding is the feeding of an infant or young child with milk from a woman's breasts. Babies have a sucking reflex that enables them to suck and milk.

With few exceptions, human breast milk is the best source of nourishment for human infants.
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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. Though boys and men have nipples, many are unaware that they also have mammary glands.
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Suction is the creation of a partial vacuum, or region of low pressure. The pressure gradient between this region and the ambient pressure will propel matter toward the low pressure area.
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Monotremata
C.L. Bonaparte, 1837

Families

†Kollikodontidae
Ornithorhynchidae
Tachyglossidae
†Steropodontidae
Monotremes (from the Greek monos 'single' + trema
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breast refers to the upper ventral region of an animal’s torso, particularly that of mammals, including human beings. The breasts of a female mammal’s body contain the mammary glands, which secrete milk used to feed infants.
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areola, plural areolae, (diminutive of Latin area, "open place") is used to describe any small circular area such as the colored skin surrounding the nipple.
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Broadly, melanin is any of the polyacetylene, polyaniline, and polypyrrole "blacks" and "browns" or their mixed copolymers. The most common form of biological melanin is a polymer of either or both of two monomer molecules: indolequinone, and dihydroxyindole carboxylic acid.
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A sex organ, or primary sexual characteristic, as narrowly defined, is any of those anatomical parts of the body which are involved in sexual reproduction and constitute the reproductive system in a complex organism; namely:

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Sexual arousal is the process and state of an animal being ready for sexual activity and feeling an urge for sexual contact.

Human sexual arousal

Unlike most animals, human beings of both sexes are potentially capable of sexual arousal throughout the year, therefore, there
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erection of the penis, clitoris or a nipple is its enlarged and firm state. It depends on a complex interaction of psychological, neural, vascular and endocrine factors. The term is also applied to the process that leads to this state.
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Peptides (from the Greek πεπτίδια, "small digestibles") are short polymers formed from the linking, in a defined order, of α-amino acids.
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Neurotransmitters are chemicals that are used to relay, amplify and modulate signals between a neuron and another cell. According to the prevailing beliefs of the 1960s, a chemical can be classified as a neurotransmitter if it meets the following conditions:

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Oxytocin (ŏk'sĭ-tō'sĭn) (Greek: "quick birth") is a mammalian hormone that also acts as a neurotransmitter in the brain. In females, it is released in large amounts after distension of the cervix and vagina during labor, and after stimulation of the
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Glands of Montgomery are sebaceous glands in the areola (of the nipple). The glands makes oily secretions (lipoid fluid) to keep the areola and the nipple lubricated and protected.

The glands become exposed and raised when the nipple is stimulated.
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Embryology is the study of the development of an embryo. An embryo is defined as any vertebrate in a stage before birth or hatching. Embryology refers to the development of the egg cell (zygote) after fertilization and the differentiation of cells into tissues and organs.
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Nipple

Information about Nipple

Anatomy

Nipples on male mammals

See also

References

Human sexual arousal