The testes are located in a skin-covered, highly pigmented, muscular sack called the
scrotum
that extends from the body behind the penis (see Figure \(\PageIndex{1}\)). This location is important in sperm production, which occurs within the testes, and proceeds more efficiently when the testes are kept 2 to 4°C below core body temperature. The dartos muscle makes up the subcutaneous muscle layer of the scrotum (Figure \(\PageIndex{2}\)).