Eccrine sweat glands (; from Greek ''ekkrinein'' '

secrete 440px Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical ...

'; sometimes called

merocrine Merocrine (or eccrine) is a term used to classify exocrine glands and their secretions in the study of histology. A cell is classified as merocrine if the secretions of that cell are excreted via exocytosis from secretory cells into an epithelia ...

glands) are the major sweat glands of the human body, found in virtually all skin, with the highest density in palm and soles, then on the head, but much less on the torso and the extremities. In other mammals, they are relatively sparse, being found mainly on hairless areas such as foot pads. They reach their peak of development in humans, where they may number 200–400/cm² of skin surface.Bolognia, J., Jorizzo, J., & Schaffer, J. (2012). Dermatology (3rd ed., pp. 539-544). hiladelphia Elsevier Saunders. They produce a clear, odorless substance,

sweat Perspiration, also known as sweating, is the production of fluids secreted by the sweat glands in the skin of mammals. Two types of sweat glands can be found in humans: eccrine glands and apocrine glands. The eccrine sweat glands are distrib ...

, consisting primarily of water. These are present from

birth Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the f ...

. Their secretory part is present deep inside the

dermis The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided i ...

. Eccrine glands are composed of an intraepidermal spiral duct, the "acrosyringium"; a dermal duct, consisting of a straight and coiled portion; and a secretory tubule, coiled deep in the

hypodermis The subcutaneous tissue (), also called the hypodermis, hypoderm (), subcutis, superficial fascia, is the lowermost layer of the integumentary system in vertebrates. The types of cells found in the layer are fibroblasts, adipose cells, and macro ...

. The eccrine gland opens out through the sweat pore. The coiled portion is formed by two concentric layer of columnar or cuboidal epithelial cells. The epithelial cells are interposed by the myoepithelial cells. Myoepithelial cells support the secretory epithelial cells. The duct of eccrine gland is formed by two layers of cuboidal epithelial cells. Eccrine glands are active in

thermoregulation Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature ...

by providing cooling from water evaporation of sweat secreted by the glands on the body surface and emotional induced sweating (anxiety, fear, stress, and pain). The white sediment in otherwise colorless eccrine secretions is caused by evaporation that increases the concentration of salts. The odor from sweat is due to bacterial activity on the secretions of the

apocrine sweat glands An apocrine sweat gland (; from Greek ''apo'' 'away' and ''krinein'' 'to separate') is composed of a coiled secretory portion located at the junction of the dermis and subcutaneous fat, from which a straight portion inserts and secretes into the ...

, a distinctly different type of sweat gland found in human skin.

Eccrine glands Eccrine sweat glands (; from Greek ''ekkrinein'' 'secrete'; sometimes called merocrine glands) are the major sweat glands of the human body, found in virtually all skin, with the highest density in palm and soles, then on the head, but much less ...

are the only sweat glands

innervated A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system. A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...

by the

parasympathetic nervous system The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The enteric nervous system is sometimes considered part of ...

, primarily by

cholinergic Cholinergic agents are compounds which mimic the action of acetylcholine and/or butyrylcholine. In general, the word "choline" describes the various quaternary ammonium salts containing the ''N'',''N'',''N''-trimethylethanolammonium cation. F ...

fibers whose discharge is altered primarily by changes in deep body temperature (core temperature), but by

adrenergic Adrenergic means "working on adrenaline (epinephrine) or noradrenaline (norepinephrine)" (or on their receptors). When not further qualified, it is usually used in the sense of enhancing or mimicking the effects of epinephrine and norepinephrine ...

fibers of the sympathetic nervous system, as well. The glands on palms and soles do not respond to temperature but secrete at times of emotional stress.

Secretion

The secretion of eccrine glands is a sterile, dilute

electrolyte solution An electrolyte is a medium containing ions that is electrically conducting through the movement of those ions, but not conducting electrons. This includes most soluble salts, acids, and bases dissolved in a polar solvent, such as water. Upon di ...

with primary components of

bicarbonate In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula . Bicarbonate serves a crucial biochemic ...

, potassium, and sodium chloride (NaCl), and other minor components such as glucose, pyruvate, lactate, cytokines, immunoglobulins, antimicrobial peptides (e.g., dermcidin), and many others. Relative to the plasma and extracellular fluid, the concentration of Na⁺ ions is much lower in sweat (~40 mM in sweat versus ~150 mM in plasma and extracellular fluid). Initially, within the eccrine glands, sweat has a high concentration of Na⁺ ions. The Na⁺ ions are re-absorbed into the tissue via the

epithelial sodium channels The epithelial sodium channel (ENaC), (also known as amiloride-sensitive sodium channel) is a membrane-bound ion channel that is selectively permeable to sodium ions (). It is assembled as a heterotrimer composed of three homologous subunits α ...

(ENaC) that are located on the apical membrane of the cells that form the eccrine gland ducts (see Fig. 9 and Fig. 10 of the reference). This re-uptake of Na⁺ ions reduces the loss of Na⁺ during the process of perspiration. Patients with the systemic

pseudohypoaldosteronism Pseudohypoaldosteronism (PHA) is a condition that mimics hypoaldosteronism. However, the condition is due to a failure of ''response'' to aldosterone, and levels of aldosterone are actually elevated, due to a lack of feedback inhibition. Types P ...

syndrome who carry mutations in the ENaC subunit genes have salty sweat as they cannot reabsorb the salt in sweat. In these patients, Na⁺ ion concentrations can greatly increase (up to 180 mmol/L). In people who have

hyperhidrosis Hyperhidrosis is a condition characterized by abnormally increased sweating, in excess of that required for regulation of body temperature. Although primarily a benign physical burden, hyperhidrosis can deteriorate quality of life from a psycholog ...

, the sweat glands (eccrine glands in particular) overreact to stimuli and are just generally overactive, producing more sweat than normal. Similarly,

cystic fibrosis Cystic fibrosis (CF) is a rare genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. Long-term issues include difficulty breathing and coughing up mucus as a result of frequent lung infections. O ...

patients also produce salty sweat. But in these cases, the problem is in the

CFTR Cystic fibrosis transmembrane conductance regulator (CFTR) is a membrane protein and anion channel in vertebrates that is encoded by the ''CFTR'' gene. Geneticist Lap-Chee Tsui and his team identified the CFTR gene in 1989 as the gene linked wi ...

chloride transporter that is also located on the apical membrane of eccrine gland ducts.

Dermicidin Dermcidin is a protein with 110 amino acids that in humans is encoded by the ''DCD'' gene. The full-length protein produces derived peptides as proteolysis-inducing factor (PIF) and other anti-microbial peptides, secreted by human eccrine sweat gla ...

is a newly isolated

antimicrobial An antimicrobial is an agent that kills microorganisms or stops their growth. Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. For example, antibiotics are used against bacteria, and antifungals ar ...

peptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A ...

produced by the eccrine sweat glands.

References

External links

A video of 3D visualization of a human eccrine gland duct
{{Authority control Skin anatomy