乳頭　　　

WordNet

a flexible cap on a babys feeding bottle or pacifier
the small projection of a mammary gland (同)mammilla, mamilla, pap, teat, tit
of or relating to or resembling papilla (同)papillose
a rubber or plastic shield to protect the nipples of nursing women

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(人間や動物の)乳首 / 乳首に似た物;《米》(ほ乳びんの)乳首

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/09/29 19:59:46」(JST)

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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, in females, breast milk is delivered to a mother's young. In this sense, it is often called a teat, especially when referring to non-humans, and the medical term used to refer to it is papilla. A breast or nipple is sometimes called a "pap".^[1] The rubber mouthpiece of a baby bottle or pacifier may also be referred to as a "nipple" or a "teat". In humans, nipples of both males and females are also one of the erogenous zones. In many cultures, human female nipples are sexualized^[2] and it is considered a taboo^[3]^[4] or a public indecency to uncover them in public.

Etymology

The word "nipple" most likely originates as a diminutive of neb, an Old English word meaning "beak", "nose", or "face", and which is of Germanic origin.^[5] The words "teat" and "tit" share a Germanic ancestor. The second of the two, tit, was inherited directly from Proto-Germanic, while the first entered English via Old French.^[6]^[7]

Anatomy

The breast: cross-section scheme of the mammary gland:
1. Chest wall
2. Pectoralis muscles
3. Lobules
4. Nipple
5. Areola
6. Milk duct
7. Fatty tissue

8. Skin

In the anatomy of mammals, a nipple, 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 dominant innervation to the nipple is derived from the lateral cutaneous branches of fourth intercostal nerve.^[8] 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 19.^[9]

In humans

Changes in size

The average projection and size of human female nipples is slightly more than 3/8 of an inch (10mm).^[10] Pregnancy and nursing tend to increase nipple size, sometimes permanently. Pregnancy also deepens the pigmentation.

Sexual activity

Nipples of both males and females are one of the erogenous zones, which are generally stimulated by hands or by mouth during foreplay, which leads to sexual arousal.^[11] The male and female breast have a similar nerve supply but the nerves lie closer together in men, whereas in a female breast they are spread out more widely.^[12] After puberty, female breasts turn more sensitive, likely due to hormonal influences.^[13] During arousal they generally become stiff, erect and protrude.

Nipple stimulation is sometimes intense enough to elicit an orgasm in some women. Research has suggested the sensations are genital orgasms caused by nipple stimulation, and may also be directly linked to "the genital area of the brain".^[14]^[15] In women, one study indicated that sensation from the nipples travels to the same part of the brain as sensations from the vagina, clitoris and cervix. Nipple stimulation may trigger uterine contractions, which then produce a sensation in the genital area of the brain.^[15]

In male mammals

A human male nipple

From conception until sexual differentiation, all mammalian fetuses within the same species look the same, regardless of sex. In humans, this lasts for around 6 weeks, after which genetically-male fetuses begin producing male hormones such as testosterone.^[16] Usually, males' nipples do not 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. This may happen whenever the testosterone level drops. Gynecomastia, although not as severe, may occur in pubescent boys undergoing physical changes due to the rapid and uncontrolled release of hormones, including estrogen. The heightened levels of estrogen in pubescent male bodies leads to the swelling of the nipple and surrounding tissue – this can often look similar to a female human nipple – and may cause slight discomfort. Thus, because the "female template" is the default for humans, the question is not why evolution has not selected against male nipples, but why it would be advantageous to select against male nipples to begin with:

The uncoupling of male and female traits occurs if there is selection for it: if the trait is important to the reproductive success of both males and females but the best or "optimal" trait is different for a male and a female. We would not expect such an uncoupling if the attribute is important in both sexes and the "optimal" value is similar in both sexes, nor would we expect uncoupling to evolve if the attribute is important to one sex but unimportant in the other. The latter is the case for nipples. Their advantage in females, in terms of reproductive success, is clear. But because the genetic "default" is for males and females to share characters, the presence of nipples in males is probably best explained as a genetic correlation that persists through lack of selection against them, rather than selection for them. Interestingly, though, it could be argued that the occurrence of problems associated with the male nipple, such as carcinoma, constitutes contemporary selection against them.

In a now-famous paper, Stephen Jay Gould and Richard C. Lewontin emphasize that we should not immediately assume that every trait has an adaptive explanation. Just as the spandrels of St. Mark's domed cathedral in Venice are simply an architectural consequence of the meeting of a vaulted ceiling with its supporting pillars, the presence of nipples in male mammals is a genetic architectural by-product of nipples in females. This idea implies men have nipples because females do.^[17]

References

^ "pap". Oxford English Dictionary (3rd ed.). Oxford University Press. September 2005. (Subscription or UK public library membership required.)
^ Todd Beer (2015-05-12). "Social Construction of the Body: The Nipple". sociologytoolbox.com. Retrieved 2015-05-16.
^ "When Did Bare Breasts Become Taboo?". Slate. 2012-09-19. Retrieved 2015-05-16.
^ Sara Sheridan (2014-11-15). "Toplessness - the one Victorian taboo that won't go away". BBC Magazine. Retrieved 2015-05-16.
^ Harper, Douglas (2001–2010). "nipple". Online Etymological Dictionary. Retrieved 15 August 2011.
^ Harper, Douglas (2001–2010). "teat". Online Etymological Dictionary. Retrieved 15 August 2011.
^ Harper, Douglas (2001–2010). "tit (1)". Online Etymological Dictionary. Retrieved 15 August 2011.
^ Grabb & Smith's Plastic Surgery 6th edition. Chapter 59 page 593
^ "The Wonder of Milk". Earthlife.net. Retrieved 2013-05-09.
^ 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
^ Winkelmann RK (1959). "The erogenous zones: their nerve supply and significance". Mayo Clin Proc 34 (2): 39–47.
^ Sarhadi NS; Shaw Dunn, J; Lee, FD; Soutar, DS (1996). "An anatomical study of the nerve supply of the breast, including the nipple and areola". British Journal of Plastic Surgery 49 (3): 156–164. doi:10.1016/S0007-1226(96)90218-0. PMID 8785595.
^ Robinson JE; Short, R V (1977). "Changes in breast sensitivity at puberty, during the menstrual cycle, and at parturition". BMJ 1 (1): 1188–1191. doi:10.1136/bmj.1.6070.1188.
^ Levay, Simon; Sharon McBride Valente (15 November 2005). Human Sexuality, Second Edition. Sinauer Associates, Inc. ISBN 978-0-87893-465-2.
^ ^a ^b Komisaruk, B. R., Wise, N., Frangos, E., Liu, W.-C., Allen, K. and Brody, S. (2011). "Women's Clitoris, Vagina, and Cervix Mapped on the Sensory Cortex: fMRI Evidence". The Journal of Sexual Medicine 8 (10): 2822. doi:10.1111/j.1743-6109.2011.02388.x. Surprise finding in response to nipple stimulation Lay summary Check |url= scheme (help) – CBSnews.com (August 5, 2011).
^ "The Developing Embryo". Gender.org/Jed Bland. Retrieved August 3, 2011.
^ Simons, Andrew M. "Why do men have nipples? Scientific American (September 17, 2003)

UpToDate Contents

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1. 授乳および離乳の一般的問題 common problems of breastfeeding and weaning
2. 小児および思春期における乳房疾患：概要 breast disorders in children and adolescents an overview
3. 乳頭分泌 nipple discharge
4. 乳房パジェット病 paget disease of the breast
5. 陥没乳頭 nipple inversion

English Journal

Partial trisomy 4q and partial monosomy 9p in a girl with choanal atresia and various dysmorphic findings.

Cakmak-Genc G1, Karakas-Celik S2, Dursun A2, Piskin İE3.
Gene.Gene.2015 Sep 1;568(2):211-4. doi: 10.1016/j.gene.2015.05.022. Epub 2015 May 13.
We report a new-born girl with partial trisomy of 4q28-qter and partial monosomy of 9p24-9ter. Our patient has choanal atresia, hypertelorism, wide nasal bridge, high arched palate, discrete nipples, heart defects, myoclonic seizures and various dysmorphic findings. Standard chromosomal analysis wit
PMID 25979671

Comparison patterns of 4 T1 antigens recognized by humoral immune response mediated by IgG and IgM antibodies in female and male mice with breast cancer using 2D-immnunoblots.

Díaz-Zaragoza M1, Hernández-Ávila R2, Govezensky T2, Mendoza L3, Meneses-Ruíz DM2, Ostoa-Saloma P4.
Immunobiology.Immunobiology.2015 Sep;220(9):1050-8. doi: 10.1016/j.imbio.2015.05.012. Epub 2015 May 18.
The early detection of cancer is one of the most promising approaches to reduce its growing burden and develop a curative treatment before the tumor is established. The early diagnosis of breast cancer is the most demanding of all tumors, because it is the most common cancer in women worldwide. We h
PMID 26026196

Correlation of astrocyte elevated gene-1, basic-fibroblast growth factor, beta-catenin, Ki-67, tumor necrosis factor-alfa with prognostic parameters in ductal carcinomas and ductal intraepithelial neoplasms.

Erdem H1, Gundogdu B, Ankarali H, Yasar M, Sener E, Oktay M, Bahadir A, Uzunlar AK, Gursan N, Ozaydin I, Sahiner C.
Nigerian journal of clinical practice.Niger J Clin Pract.2015 Sep-Oct;18(5):638-43. doi: 10.4103/1119-3077.158961.
BACKGROUND: Breast cancer is the second most frequent cancer in the world. Although it is widely accepted that the etiology of breast cancer includes both genetic and environmental factors, the molecular mechanism of its development and progression remains poorly understood, and thus far, no specifi
PMID 26096243

Change in the hedonic value of an aversive stimulus in the presence of a pre-exposed odor.

Kamenetzky GV1, Suárez AB2, Pautassi RM3, Mustaca AE2, Nizhnikov ME4.
Physiology & behavior.Physiol Behav.2015 Sep 1;148:51-7. doi: 10.1016/j.physbeh.2014.12.041. Epub 2014 Dec 24.
Rats exhibit a sensitive period from the time of birth until postnatal day 10 during which they develop preferences for odors even if those odors are paired with a moderately aversive stimulus. It is still unknown whether pre-exposure to an odor produces alterations on intake responses of basic tast
PMID 25543090

Japanese Journal

分娩直後のカンガルーケア(BKC)のプロセスと所要時間

神谷摂子,高橋弘子,恵美須文枝
日本保健科学学会誌 15(3), 121-131, 2012-12-25
本研究はBKC中の児の行動を観察し,どのような経過でそれぞれのステージが進行し,また,それぞれのステージが次の段階に移行するまでの所要時間はどれくらいかかるのかを明らかにすることを目的に,2003年7〜9月までに正常分娩し,研究への参加に同意が得られた母子10例を対象に,児娩出場面からBKC終了又は児が入眠傾向になった時点までを観察記録とビデオ撮影による参加観察を行った。分析は,BKC中の児の動作 …
NAID 110009561816

P1-031 Nipple stimulationとMamma massageによる分娩(Group2 分娩,ポスターセッション)

小倉真由美,鬼澤宏美
母性衛生 53(3), 233, 2012-11-16
NAID 110009608884

Modeling and Optimization of Sub-Wavelength Grating Nanostructures on Cu(In,Ga)Se2 Solar Cell

Kuo Shou-Yi,Hsieh Ming-Yang,Lai Fang-I [他],Liao Yu-Kuang,Kao Ming-Hsuan,Kuo Hao-Chung
Jpn J Appl Phys 51(10), 10NC14-10NC14-3, 2012-10-25
… From the simulation results, AZO structures with nipple arrays effectively suppress the Fresnel reflection compared with nanorod- and cone-shaped AZO structures. …
NAID 40019455962