Sweat GlandEdit
Sweat glands are specialized exocrine structures in the skin that play a central role in maintaining body temperature, fluid balance, and, in some contexts, skin odor. They are distributed across the body in varying densities and come in distinct types with different functions and regulatory mechanisms. These glands are a classic example of how evolution equips an organism with rapid, responsive means to interact with its environment—balancing energy expenditure, hydration, and microbial ecology on the surface of the body.
In humans, the two primary categories of sweat glands are eccrine glands and apocrine glands. Each type contributes to the overarching system of thermoregulation and skin homeostasis, while also supporting region-specific functions tied to hair-bearing skin and social signaling in certain contexts. For more on the basic tissues involved, see skin and for the chemical secretions themselves, see sweat.
Structure and distribution
Eccrine glands
Eccrine glands are small, coiled, tubular glands that open to the surface of the skin via sweat pores. They are widely distributed, with high densities on the palms, soles, and forehead, and are present across most skin surfaces. Their primary product is a clear, watery secretion rich in water and electrolytes, which evaporates from the skin to facilitate cooling. The secretory portion lies in the dermis or hypodermis, and the duct traverses the dermis to the surface. See eccrine gland for more detail.
Apocrine glands
Apocrine glands are larger and are located mainly in hair-bearing areas such as the axillae and groin. They secrete a thicker fluid into the hair follicle canal. This secretion becomes noticeable in humans mainly after puberty and can contribute to body odor through bacterial metabolism on the skin surface. The regulatory logic and contribution of apocrine sweat to olfactory cues are topics of ongoing study. See apocrine gland for additional context.
Myoepithelial cells and ducts
Surrounding the secretory units of both major gland types are myoepithelial cells, which contract to expel sweat into the ducts. This mechanism helps regulate the rate of secretion in response to physiological demand. See myoepithelial cell for more.
Distribution across the body
While eccrine glands are ubiquitous, apocrine glands are more regionally concentrated. The pattern of distribution interacts with clothing, activity level, climate, and metabolic state to determine sweating patterns in daily life.
Physiology and regulation
Thermoregulation
The primary function of sweating is evaporative cooling. As sweat evaporates from the skin, heat is carried away, helping to maintain stable core temperature during activity or exposure to heat. See thermoregulation for the broader physiological framework.
Secretory composition and excretion
Sweat consists largely of water with dissolved salts (electrolytes), urea, and trace metabolites. The exact composition can vary by gland type, region, and physiologic state. This excretion contributes to fluid and electrolyte balance and can influence cutaneous microenvironments.
Neural and hormonal control
Sweat secretion is driven by the autonomic nervous system, predominantly through sympathetic cholinergic fibers releasing acetylcholine onto muscarinic receptors of the glands. Hormonal and local factors can modulate sweating rate in response to environmental and metabolic demands. See autonomic nervous system and muscarinic receptor for related concepts.
Odor and skin microflora
Apocrine secretions become associated with body odor primarily through the activity of skin bacteria. The odorless precursor secretions are transformed by bacterial metabolism into volatile compounds; this interaction is influenced by genetics, microbiome composition, and personal hygiene practices. See bromhidrosis and microbiome for related topics.
Development, evolution, and variation
Sweat glands develop relatively early in vertebrate skin and expand in density and function as organisms adapt to environments where efficient cooling is advantageous. Across mammals, gland density and activity reflect evolutionary trade-offs among cooling efficiency, water availability, and metabolic rate. In humans, eccrine glands have become a key feature supporting endurance activity in diverse climates, while apocrine glands reflect other social and ecological functions tied to hair-bearing skin. See evolution and comparative anatomy for broader perspectives.
Clinical significance and notable conditions
Hyperhidrosis: a condition characterized by excessive sweating beyond thermoregulatory needs, often affecting the palms, soles, or axillae. Treatments range from topical antiperspirants containing aluminum compounds to procedures such as botulinum toxin injections or, in severe cases, sympathectomy. See hyperhidrosis for more details.
Hypohidrosis and anhidrosis: reduced or absent sweating, which can impair cooling and increase thermoregulatory risk in hot environments. Causes include genetic disorders, nerve injury, and certain medications. See anhidrosis and hypohidrosis.
Bromhidrosis: objectionable body odor arising from bacterial breakdown of sweat, particularly in regions rich in apocrine glands. Management includes hygiene, topical antimicrobials, and addressing contributing factors. See bromhidrosis.
Related skin conditions: disorders of hair follicles, sebaceous activity, or surrounding skin can interact with sweat gland function. For example, hidradenitis suppurativa involves inflammation around hair follicles and associated structures in apocrine-rich regions. See hidradenitis suppurativa.
Diagnostic and therapeutic research: ongoing studies examine the regulatory networks that govern sweating, including neural signaling pathways and hormonal influences, as well as novel approaches to modulating gland activity through pharmacology or targeted therapies. See neurophysiology and pharmacology for context.