How Does a Human Sweat Gland Work?
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About Sweating
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Sweating is one of the ways that the human body regulates temperature. This can be in response to a rise in external temperature, or in internal temperature, from a fever, muscle exertion, or even anxiety. When the hypothalamus, an important gland in the brain, receives feedback that the body is hot, it sends signals to the sweat glands to begin pulling water and electrolytes from the body. Myoepithelial cells around the gland contract, forcing the sweat glands to discharge the fluid. The excretion and evaporation of sweat causes the body to cool.
Merocrine Sweat Glands
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Merocrine sweat glands are the most numerous in the body; an adult has approximately 3 million of them. While merocrine sweat glands are located all over the body, the palms of the hands and soles of the feet have the highest concentration of them. The degree to which one sweats is determined by both hormonal and neural feedback. Sweat produced by the merocrine glands is 99 percent water, with a small amount of electrolytes. One of these electrolytes, sodium chloride, gives sweat its salty taste.
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Apocrine Sweat Glands
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Apocrine sweat glands are larger than merocrine glands, and they extend more deeply into the dermis. The apocrine glands are only in the armpits, groin and around the nipples, and they don't become active until puberty. Unlike merocrine glands, which discharge sweat onto the skin, apocrine glands discharge sweat into a hair follicle. Sweat produced by these glands is thicker, cloudier, and may have an odor. There is some evidence that they may also give off pheromones, but more research is needed.
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Resources
- Photo Credit Diagram of dermal layers with sweat gland; National Institutes of Health.
