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 male testes produce male sex cells called sperm. The hypothalamus and the pituitary gland in the brain control the production of sperm and male sex hormones in the testes.Negative feedback systems ensure that the number of sperm cells and constant levels of testosterone are maintained.he male testes produce male sex cells called sperm. The hypothalamus and the pituitary gland in the brain control the production of sperm and male sex hormones in the testes.