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).
View Full Document. It is necessary for the testes to be kept below body temperature for abundant, viable sperm formation. True ï· A scrotal muscle that contracts in response to cold environmental temperature is the cremaster. True ï· Which of these male accessory ducts transports both sperm cells and urine? urethra.