Melasma Overview. Patches of melasma are darker than other areas of skin because they have more pigment. The cells that produce pigment in the skin are called melanocytes. Ultraviolet radiation, or UV rays, from the sun stimulate melanocytes to produce pigment.
The human testicle .The two muscles that regulate the temperature of the testes are the dartos andcremaster muscles:â¢ Dartos Muscle The dartos muscle is a layer of smooth muscle fibers in the subcutaneous tissue of thescrotum (surrounding the scrotum).
Thermal Regulation of the Testes. Successful spermatogenesis is achieved at temperatures a few degrees below core body temperature. The extra-abdominal location of the testes is critical to spermatogenesis. The testes may be several Celsius degrees cooler than core body temperature. Testicular Descent: In a number of mammalian species, including humans, the testes are extra-abdominal.