We have two types of sweat glands: eccrine and apocrine. The body has thousands of eccrine glands all over the place, which effectively regulate the body's temperature. As our temperature rises, the nervous system goes to work to stimulate the eccrine glands to release sweat. In a way, we are almost always sweating, even if we don’t notice it! Apocrine glands are found under the arms and groin areas. Although the body's temperature can stimulate these glands, they are also triggered by stress, anxiety, or hormonal imbalances. The apocrine glands also produce bacteria that help break down the sweat, which causes body odor. That's why we just put deodorant under the arms rather than all over the body!
Basically, the sweat gland is a long, coiled, hollow tube of cells. The coiled part in the dermis is where sweat is produced, and the long portion is a duct that connects the gland to the opening or pore on the skin’s outer surface. Nerve cells from the sympathetic nervous system connect to the sweat glands.
When a sweat gland is stimulated, the cells secrete a fluid, or primary secretion, that is similar to plasma, as it is mostly water and has high concentrations of sodium and chloride. The source of this fluid is the spaces between the cells, which get the fluid from the blood vessels in the dermis. This fluid travels from a coiled portion up through a straight duct. In apocrine glands, sweat is produced in the same way. However, the sweat from apocrine glands also contains proteins and fatty acids, which make it thicker and give it a milky or yellowish color. This is why underarm stains in clothing appear yellowish!
Why Sweating is Good For You
When sweat evaporates from the surface of your skin, it removes excess heat and cools you. This is due to a neat principle in physics, called the heat of vaporization. However, not all of the sweat evaporates, rather it runs off your skin. In addition, not all heat energy produced by the body is lost through sweat. Some is directly radiated from the skin to the air or absorbed through respiratory surfaces.
Simulation with a Paper Cup
We can simulate the rising temperature in an animal’s body with some boiling water in a paper cup. While the hot water evaporates, the cup cools down, allowing it to stay intact and not break down under the heat. Try it out at home! Here’s what you’ll need:
- Several plain paper cups (without wax coating)
- Several styrofoam cups
- Stove burner
- Dry sand
- Tongs to hold the cups
Step One: Turn the burner on medium heat.
Step Two: Fill a paper cup nearly to the brim with water.
Step Three: Using tongs, hold the cup of water about six inches above the heating element.
Step Six: repeat the last three steps with some sand in a paper cup and then water in a styrofoam cup. What differences can you observe?
Keil, Ernst. “The Garden Arbor”. Released into the public domain. Uploaded on 6/30/17 from commons.wikimedia.org
“Sweating at Wilson Trail Stage One”. Released into the public domain. Uploaded on 6/30/17 from commons.wikimedia.org
“Close Up of Drink”. Released into the public domain. Uploaded on 6/30/17 from pexels.com
Michuda, Dave. “Red Ceramic Mug”. Released into the public domain. Uploaded on 6/30/17 from pexels.com