Scrotum
In male animals, the scrotum is an external bag of skin and muscle containing the testicles. It is an extension of the abdomen, and is located between the penis and anus.
The function of the scrotum appears to be to keep the testicles at a temperature slightly lower than that of the rest of the body. For the human, a temperature around 94 degrees Farenheit appears to be ideal; 98-degree temperatures may be damaging to sperm count. The temperature is controlled by making the scrotum tighter, hence moving the testicles closer to the abdomen, when it is cold, and conversely, through the cremasteric reflex, the gradual tightening and loosening of the cremaster muscle in the abdomen and the dartos fascia (muscular tissue under the skin) in the scrotum.
See also: perineum, sex organ, castration
