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).
Core temperature is regulated by the hypothalamus (in the brain), which is often called the bodys thermostat. The hypothalamus responds to various temperature receptors located throughout the body and makes physiological adjustments to maintain a constant core temperature.For example, on a hot day, temperature receptors located in the skin send signals to the hypothalamus to cool the body by increasing the sweat rate.he hypothalamus responds to various temperature receptors located throughout the body and makes physiological adjustments to maintain a constant core temperature. For example, on a hot day, temperature receptors located in the skin send signals to the hypothalamus to cool the body by increasing the sweat rate.