Last week, we discussed how thermal conduction heats things up. When objects get hot, there’s no real cooling system to bring their surface temperature back down, other than exposure to cooler air over time. But for animals and humans, there are a lot of steps involved. Many people view sweat as a nuisance: it can leave stains on our clothes and it often smells anything other than pleasant. However, sweating is a crucial biological function, and if we didn’t sweat, things could get very ugly very quickly. If the body didn’t have a way to cool itself off, we could constantly be suffering from heat exhaustion and even heat stroke.
How is Sweat Produced?
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.
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.
Sweating is also one of your body’s ways of getting rid of toxins. When we sweat, trace amounts of toxins are released onto the surface of your skin, instead of festering around in your body. The main toxin released in sweat is phthalates, which are found in plastics, fragrances, cosmetics, and paints. However, lots of salts and other necessary minerals are also lost in sweat. When the water in the sweat evaporates, it leaves the salts behind on your skin, which is why your skin tastes salty. The loss of excessive amounts of salt and water from your body can quickly dehydrate you, which can lead to circulatory problems, kidney failure and heat stroke. So, it is important to drink plenty of fluids when you exercise or are outside in high temperatures. Sports drinks contain some salts to replace those lost in the sweat, and sometimes are more tasty than water!
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:
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
- Water
- 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 Four: Continue holding the cup over the heat. The paper or burn, or the water will boil.
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?
References:
http://health.howstuffworks.com/skin-care/information/anatomy/how-sweat-works3.htm
https://www.education.com/science-fair/article/boiling-water-paper-cup/
Image Credits:
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
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?
References:
http://health.howstuffworks.com/skin-care/information/anatomy/how-sweat-works3.htm
https://www.education.com/science-fair/article/boiling-water-paper-cup/
Image Credits:
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
