Scanning electron micrograph of skin from a human finger, showing a sweat pore. The picture, centre, shows the entrance pore that leads down to the (unseen) gland beneath. The pore displays a spiral structure at the surface of the epidermis. Sweat glands on the hands are eccrine glands that secrete a very dilute solution of salts, lactic acid and urea. Their function is to regulate body temperature. Their greatest density is found on the hands and feet, with 600-700 glands per square centimetre. The action of the glands is mediated by the central nervous system in response to a rise in body temperature due to environmental factors (e.g.hot weather) or physical exercise. Failure to sweat, a condition known as anhidrosis, may lead to heat intolerance; weakness, dizziness, fatigue, or difficulty in breathing. In extreme cases, death from hyperthermia may ensue. Mag x 440 at 10x8