Nepedia
Back to Discover
Advanced Reader
🧬

Perspiration

life science Maturity 11-13 Next article →

Perspiration, commonly called sweat, is a fluid secreted by specialized glands in the skin of mammals. It plays a vital role in maintaining a stable internal environment. In humans, this process is primarily used for thermoregulation. This is the biological mechanism used to control body temperature. Without effective sweating, the body could easily overheat during physical exertion or in hot weather.

TranspirationPerspirationCommonsFL
TranspirationPerspirationCommonsFL

The human body utilizes two distinct types of sweat glands. The first type is the eccrine glands. These are distributed across most of the body. They secrete a watery, brackish fluid that is mostly water. The second type is the apocrine glands. These are restricted to specific areas like the armpits. They produce an oily, opaque, and odorless secretion. While the secretion itself has no smell, it gains a characteristic odor when bacteria on the skin begin to decompose it.

Thermoregulation is a complex, step-by-step process managed by the brain. The hypothalamus, located in the preoptic and anterior regions of the brain, acts as the control center. It contains thermosensitive neurons that monitor temperature. When the core temperature rises, the hypothalamus triggers the sympathetic nervous system. Specifically, sympathetic cholinergic neurons release acetylcholine to stimulate the sweat glands. This causes the eccrine glands to release water-rich sweat onto the skin surface.

Sweaty runner
Sweaty runner

Once the sweat reaches the skin, evaporative cooling begins. This is the primary way the body loses heat. As high-energy molecules evaporate from the skin, they release the heat they absorbed from the body. This process cools the skin and the superficial blood vessels. The cooled venous blood then returns to the body's core. This circulation helps counteract rising internal temperatures. This system responds to both physical heat and emotional stress. Emotional sweating is often limited to the palms, soles, and armpits. Physical heat-induced sweating occurs throughout the entire body.

Sweat is not composed of pure water; it contains 0.2% to 1% solute. These solutes include minerals like sodium, chloride, and potassium. The amount of water lost can vary greatly. During average intensity exercise, sweat losses can reach specific hourly rates. In humans, sodium concentration in sweat ranges from 30 to 65 mmol/L. When people move from cold to hot climates, they undergo acclimatization. During this process, the maximum sweat rate increases. However, the concentration of solutes like sodium decreases to conserve minerals.

Some animals use different methods to manage their heat. Most mammals have sweat glands, but very few use them for cooling. Dogs, for example, regulate temperature by panting. This evaporates water from the moist lining of the oral cavity and pharynx. Horses are a unique exception among mammals. They use apocrine glands to produce sweat containing a protein called latherin. Because horses have thick, waterproof coats, they need this protein to act as a wetting agent. Latherin helps the sweat move from the skin to the surface of the hair so it can evaporate.

Sweaty runner
Sweaty runner

Sometimes, the sweating process can become abnormal. Hyperhidrosis is a condition characterized by excessive sweating. It is often inherited and can affect the whole body or specific areas like the hands and feet. While not life-threatening, it can impact a person's quality of life. Other conditions can cause sweating, such as fever, menopause, or even intense emotions. In medical contexts, diaphoresis refers to sweating that may be a sign of an underlying issue. This could include anything from a simple fever to more serious conditions like a heart attack or infections like malaria.

581 words

Where will your curiosity go next?

Keep exploring at your chosen reading level.

🖼️ Images & Media (3)
File:Brendon Ayanbadejo by Keith Allison 2 (cropped).jpg
Brendon Ayanbadejo by Keith Allison 2...
File:Sweaty runner.jpg
Sweaty runner.jpg
File:TranspirationPerspirationCommonsFL.jpg
TranspirationPerspirationCommonsFL.jpg
More to explore

🔬 Go deeper

More advanced topics to explore

🪜 Step back

Simpler topics to build understanding

What is Nepedia?

A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.