Testes! One, two...three???

We are currently studying the reproductive system in class. Here is some fun trivia about the testes. The information was gathered from Wikipedia.

In land mammals, with the exception of the elephant the testes are located outside of the body, as they are suspended by the spermatic cord and within the scrotum. This is due to the fact that The cremasteric muscle is part of the spermatic cord. When this muscle contracts, the cord is shortened and the testicle is moved closer up toward the body, which provides slightly more warmth to maintain optimal testicular temperature. When cooling is required, the cremasteric muscle relaxes and the testicle is lowered away from the warm body and are able to cool. This phenomenon is known as the cremasteric reflex. It also occurs in response to stress (the testicles rise up toward the body in an effort to protect them in a fight), and there are persistent reports that relaxation indicates approach of orgasm. There is a noticeable tendency to also retract during orgasm.

The testicles can also be lifted voluntarily using the pubococcygeus muscle, which partially activates related muscles. This can sometimes be triggered by tightening or sucking in the stomach or abdomen.

Animals other than mammals do not have externalized testicles. Birds, despite having very high core body temperatures have internal testes: it was once theorized that birds used their air sacs to cool the testes internally, but later studies revealed that birds' testes function at core body temperature.[1] Marine mammals also have internal testes, but it has recently been shown (eg, for dolphins) that they use elaborate vascular networks to provide the necessary temperature lowering for proper operation.

The seminiferous tubules of the testes are the starting point for the process of spermatogenesis, where stem cells adjacent to the inner tubule wall divide in a centripetal direction - beginning at the walls and proceeding into the lumen to produce immature sperm.