stimulation. Like eccrine glands, they continuously secrete a thin, watery sweat. Others Specialized sweat glands, including the ceruminous glands, mammary glands, ciliary glands of the eyelids, and sweat glands of the nasal vestibulum, are modified apocrine glands. Ceruminous glands are near the ear canals, and produce cerumen (earwax) that mixes with the oil secreted from sebaceous glands. Mammary glands use apocrine secretion to produce milk. Sweat Sweat glands are used to regulate temperature and remove waste by secreting water, sodium salts, and nitrogenous waste (such as urea) onto the skin surface. The main electrolytes of sweat are sodium and chloride, though the amount is small enough to make sweat hypotonic at the skin surface. Eccrine sweat is clear, odorless, and is composed of 98–99% water; it also contains NaCl, fatty acids, lactic acid, citric acid, ascorbic acid, urea, and uric acid. Its pH ranges from 4 to 6.8. On the other hand, the apocrine sweat has a pH of 6 to 7.5; it contains water, proteins, carbohydrate waste material, lipids, and steroids. The sweat is oily, cloudy, viscous, and originally odorless; it gains odor upon decomposition by bacteria. Because both apocrine glands and sebaceous glands open into the hair follicle, apocrine sweat is mixed with sebum. Mechanism Both apocrine and eccrine sweat glands use merocrine secretion, where vesicles in the gland released sweat via exocytosis, leaving the entire cell intact. It was originally thought that apocrine sweat glands use apocrine secretion due to histological artifacts resembling "blebs" on the cell surface, however, recent electron micrographs indicate that the cells use merocrine secretion. In both apocrine and eccrine sweat glands, the sweat is originally produced in the gland's coil, where it is isotonic with the blood plasma there. When the rate of sweating is low, salt is conserved and reabsorbed by the gland's duct; high sweat rates, on the other hand, lead to less salt reabsorption and allow more water to evaporate on the skin (via osmosis) to increase evaporative cooling. Secretion of sweat occurs when the myoepithelial cell cells surrounding the secretory glands contract. Eccrine sweat increases the rate of bacterial growth and volatilizes the odor compounds of apocrine sweat, strengthening the latter's acrid smell. Normally, only a certain number of sweat glands are actively producing sweat. When stimuli call for more sweating, more sweat glands are activated, with each then producing more sweat. Stimuli Thermal Both eccrine and apocrine