sentences:  They reach their peak of development in humans, where they may number 200–400/cm² of skin surface.They produce a clear, odorless substance, sweat, consisting primarily of water.Eccrine glands are composed of an intraepidermal spiral duct, the "acrosyringium"; a dermal duct, consisting of a straight and coiled portion; and a secretory tubule, coiled deep in the dermis or hypodermis.