Science Questions

Why do the male private parts shrink in cold weather?

Sun, 28th Nov 2010

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Question

@NeilDenham1978 asked:

I am not sure quite how to phrase this... but in this very cold weather why do the male private parts shrink so much?

Answer

Chris -   There is actually a physiology behind this.  Itís not just people claiming this and making up.  It is true, honest.  And the reason for this is in fact, the rate at which sperm is made in the testes occurs optimally at a temperature which is 1 degree below body temperature, so about 36 degrees where normal body temperature is 37 degrees C and that's why they dangle down in a little bag to keep them a little bit cooler than body temperature.  Sperm actually can be stored and lives quite happily at a higher temperature and so thatís why when a sperm has been made, itís moved up inside the body to structures called the seminal vesicles where itís nourished and kept alive until itís needed.  But the actual synthetic process occurs better at the lower temperature and that's why the testes are dangling down.  And you have supplying or enveloping, wrapping around the testes in the scrotum, you have muscles called the cremaster muscles and thereís a reflex called the cremaster reflex which shortens those muscles to bring the testes up closer to the body when they're cold, but also when you're scared for obvious reasons, because terror can mean you have to run away or you might get booted somewhere sensitive, so you can elevate them.  And so, you bring them up, closer to the body when you are cold and you drop them down a bit when you are too hot to keep the temperature right for making sperm at the right rate.  So that's why things tend to get a warmer blood flow closer to the body and therefore, appear to shrink when itís cold, and they dangle down a bit further when itís a bit warmer.  So there is some real sound science behind this.

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