The scrotum (SKROH-tum), or scrotal sac, is a loose pouch of skin that is an outpocket — ing of the abdominal wall in the groin area directly underneath the penis (I Figure 4.3).
When I took swimming classes in high school, the trip back to the locker room was always a bit traumatic. After peeling off my swimsuit, it seemed like I had to search around for my balls. The other guys seemed to have the same problem, since they were also frantically tugging and pulling to get everything back in place. (authors’ files)
Another kind of stimulation that causes the scrotum to draw closer to the body is sexual arousal. One of the clearest external indications of impending male orgasm is the drawing up of the testes to a position of maximum elevation. The major scrotal muscle involved in this response is the cremasteric muscle. Sudden fear can also cause strong contractions of this muscle, and it is also possible to initiate contractions by stroking the inner thighs. This response is known as the cremasteric reflex.