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 testes work best at temperatures slightly less than core body temperature. The spermatogenesis is less efficient at lower and higher temperatures than 33 Â°C. This is presumably why the testes are located outside the body. There are a number of mechanisms to maintain the testes at the optimum temperature.