I've done some research and I figured out that the two muscles of the scrotal sac, the dartos and cremaster muscles contracts involuntarily when it is cold to move the testes closer to the heat of the body in the pelvic region causing the scrotum to appear slightly wrinkled.

But I've also noticed that it also occurs when preparing to defecate and then when I'm done, it relaxes.

Why does it occur and is there any biological or scientific evidence as to why it happens?


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