A suitable temperature is maintained inside the testes by involuntary movements of the muscles that connect the scrotum to the body wall. Why scrotum is called as temperature regulator of testis ?

Explanation

Scrotum is a place where testis begins to descend during the third month with a concomitant (existing or occuring together) shortening of gubernaculum. The descent of testis is under the control of testosterone and gonadotropin. Proper. descend is essential for complete fertility because sperm needs low temperature by about `2^@C` from normal body temperature `(37^@C)` to mature than the abdominal temperature. Therefore if the testis do not descend from the abdominal cavity to scrotum the heat higher temperature (which is incompatible to spsrmatogenesis) destroy the sperm producing seminiferous tubule resulting in sterility. Heat does not harm the interstitial cells.