Why do men have nipples?

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185248

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What else would you pierce when your feeling horny?....Oh yeah....that :)
 

AquaEyes11010

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Technically as a fetus, you have all the parts to become a man or a woman. It's the presence of one gene (located as might be expected on the Y sex chromosome) that determines which of two tubes survive to form the internal sex organs to form, which guides one organ to develop the external anatomy.

Just to clear that up. ;) the penis and testicles may not extend during fetal development and the external anatomy may not be complete until later periods, but we all start at the same place and that is being neither male nor female. You could think of it as bipotential sex determinations. And technically, its the lack of the SRY gene found in males that makes the fetus into a female.

It's interesting stuff. With the formation of different internal sex organs, you have the formation of different hormones that clearly have very different effects on males and females. Physically. Males do not have mammary glands, but they do have nipples. Same with females until they reach puberty when progesterone stimulates various events, including, well, "formation"of tits.

One thing I did not was that men could lactate. You learn something new every day.

And my post may not be completely accurate, I'm going by what I remembered on Human Anatomy and Physiology. The reproductive system is what I knew best out of that whole class. :)



Becoming male is about more than masculinization. It also requires defeminization. Before sexual differentiation, we are NOT "female by default." We have a neutral default, and the presence of the SRY gene initiates masculinization and defeminization, but it involves many steps. Males typically lose their Mullerian ducts, while females typically lose their Wolffian ducts. True, without the SRY gene to get things started, external genitalia will resemble that of a female, but internal anatomy (uterus, ovaries, oviducts) requires additional input. Mutations along the way can allow masculinization but not initiate defeminization. People who are XY but lack receptors for androgen will look outwardly female because their body didn't masculinize, but internally they have testes and lack a uterus (because they DID defeminize). Or individuals lacking the SRY gene can display masculinizing effects on the body as a result of mutations in genes involved in the steps to produce cortisol.

Nipples are an example of something conserved in the neutral default which develop initially, but mature into functional "milk dispensers" with the additional influence of hormones which begin when the hypothalamus kick-starts puberty and starts production of estrogen in the ovaries. Without this added influence, they remain without developing further.

:)
 
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185248

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Because we would look funny with 1 nipple? Then I would not be able to have the sensation of one holed and one not....Gasp...horror...
 

Catharsis

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Becoming male is about more than masculinization. It also requires defeminization. Before sexual differentiation, we are NOT "female by default." We have a neutral default, and the presence of the SRY gene initiates masculinization and defeminization, but it involves many steps. Males typically lose their Mullerian ducts, while females typically lose their Wolffian ducts. True, without the SRY gene to get things started, external genitalia will resemble that of a female, but internal anatomy (uterus, ovaries, oviducts) requires additional input. Mutations along the way can allow masculinization but not initiate defeminization. People who are XY but lack receptors for androgen will look outwardly female because their body didn't masculinize, but internally they have testes and lack a uterus (because they DID defeminize). Or individuals lacking the SRY gene can display masculinizing effects on the body as a result of mutations in genes involved in the steps to produce cortisol.

Nipples are an example of something conserved in the neutral default which develop initially, but mature into functional "milk dispensers" with the additional influence of hormones which begin when the hypothalamus kick-starts puberty and starts production of estrogen in the ovaries. Without this added influence, they remain without developing further.

:)
lol! I'm glad someone knew what I was talking about. I didn't really want to get into such technical details for a thread that could be more hot than smart. ;) Although, I was under the assumption that both ducts will develop into the internal sexual organs (until the Wolffian duct descends out of the body as testes in males), and the hormonal guidance from these organs will determine the external anatomy from the bipotential gonad in the fetus.

Nevertheless, my only only point was to broadly discuss that the belief that everyone starts out as female is not necessarily true, which you also mentioned (refer to the bolded part of your post), albeit in a much simpler way than I did. :)
 

bobbyboyle

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Becoming male is about more than masculinization. It also requires defeminization. Before sexual differentiation, we are NOT "female by default." We have a neutral default, and the presence of the SRY gene initiates masculinization and defeminization, but it involves many steps. Males typically lose their Mullerian ducts, while females typically lose their Wolffian ducts. True, without the SRY gene to get things started, external genitalia will resemble that of a female, but internal anatomy (uterus, ovaries, oviducts) requires additional input. Mutations along the way can allow masculinization but not initiate defeminization. People who are XY but lack receptors for androgen will look outwardly female because their body didn't masculinize, but internally they have testes and lack a uterus (because they DID defeminize). Or individuals lacking the SRY gene can display masculinizing effects on the body as a result of mutations in genes involved in the steps to produce cortisol.

Nipples are an example of something conserved in the neutral default which develop initially, but mature into functional "milk dispensers" with the additional influence of hormones which begin when the hypothalamus kick-starts puberty and starts production of estrogen in the ovaries. Without this added influence, they remain without developing further.

:)
Great explanation :smile: