Eccrine glands are the most common type of sweat gland, distributed widely across the skin surface. They are found in higher concentrations on areas like the palms, soles of the feet, and the forehead. Present from birth, these small yet abundant glands play a key role in skin function.
Regulating Body Temperature
The primary function of eccrine glands is regulating body temperature, a process known as thermoregulation. When the body’s internal temperature rises, such as during physical activity or exposure to hot environments, these glands release water onto the skin’s surface. This secreted water, known as sweat, then evaporates. This evaporation effectively removes heat from the body, leading to a cooling effect on the skin and underlying blood.
Maintaining a stable core body temperature is crucial for human health, and eccrine sweat glands are the primary means of achieving this. Without proper thermoregulation, prolonged physical exertion or high ambient temperatures can lead to overheating, resulting in heat exhaustion or even heatstroke. The body’s ability to produce large volumes of sweat allows it to dissipate excess heat and prevent dangerous temperature increases.
How Eccrine Glands Produce Sweat
Eccrine glands have a coiled secretory portion deep within the dermis or hypodermis, and a duct extending to a sweat pore on the skin surface. The secretory coil contains clear cells, dark cells, and myoepithelial cells. Sweat production begins in the clear cells, where fluid is secreted from blood plasma. This initial fluid is isotonic, meaning it has a similar concentration of solutes to blood plasma.
The process involves the active transport of ions, particularly sodium and chloride, into the gland’s lumen. Water then follows these ions osmotically to balance the solute concentration. As this fluid moves through the coiled duct, cells lining the duct reabsorb some sodium and chloride ions. This reabsorption reduces the electrolyte concentration, resulting in the hypotonic (less concentrated) sweat released onto the skin. Sweat production is primarily stimulated by the sympathetic nervous system.
The Makeup and Importance of Eccrine Sweat
Eccrine sweat is predominantly water, constituting over 99% of its composition, making it clear and odorless. Beyond water, it contains various dissolved components, including electrolytes such as sodium, potassium, and chloride ions. The concentration of sodium ions in sweat is considerably lower than in blood plasma due to reabsorption in the sweat duct.
Other minor components in eccrine sweat include metabolic byproducts like lactic acid and urea, as well as trace amounts of glucose, bicarbonate, and amino acids. While thermoregulation is the primary role of eccrine sweat, these components contribute to secondary functions. For instance, lactate, urea, and electrolytes help maintain skin hydration and act as natural moisturizing factors for the stratum corneum, the outermost layer of the skin. Additionally, sweat serves as a minor excretory route for some waste products.