The scrotum is the bag that holds the testicles in male mammals. It is made of skin and muscle and is found between the penis and anus. It is often covered in pubic hair and becomes tight when the male is aroused. Informally it is called a ballbag or ballsack.
The function of the scrotum is to keep the testicles less warm than the rest of the body. Human testicles work best at 36.8 degrees Celsius (98 degrees Fahrenheit) when normal body temperature is 37 degrees Celsius (98.6 degrees Fahrenheit). Higher temperatures than 36.8 degrees will damage the sperm inside the testicles.
The temperature is controlled by moving the testicles closer to the abdomen when they are too cold, and away when too hot. This is done by muscles contracting or relaxing. This lifts and lowers the testicles inside the scrotum. They can also be lifted by tightening the anus and pelvic muscles.
The best temperature for the testes varies between species, but usually it's a bit cooler than body temperature. This means that the testicles always have to be held outside of the body.
Another explanation is to protect the testes from jolts and being crushed inside the body. Animals that have slow movements - such as elephants, whales, and moles - have internal testes and no scrotum.
Other pages [change]