What is regulates the temperature for testes?

The temperature of the testes is regulated by the dartos muscle and cremaster muscle. The dartos muscle is a thin layer of muscle that lies just beneath the skin of the scrotum. It contracts when the temperature is too cold, pulling the testes closer to the body to keep them warm. The cremaster muscle is a thicker layer of muscle that lies deeper within the scrotum. It contracts when the temperature is too hot, relaxing the testes to allow them to hang down away from the body to cool off.