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).
The testicles (also called testes) are part of the male reproductive system. 1  The testicles are two oval organs that are located inside the scrotum, the loose sac of skin that hangs behind the penis. 2  The testicles make the male hormones, including testosterone, and produce sperm, the male reproductive cells. The testicles are two oval organs that are located inside the scrotum, the loose sac of skin that hangs behind the penis. 2  The testicles make the male hormones, including testosterone, and produce sperm, the male reproductive cells.