Eccrine sweat gland
Hypodermis & appendages · Sympathetic cholinergic M3 receptor CFTR in duct
Two to four million simple coiled tubular glands distributed over almost the whole body surface, with a secretory coil at the dermal-hypodermal border and a duct spiralling up through the epidermis. They are the body's principal effector for evaporative heat loss.
Traced from the start
Detail
- Innervation
- Sympathetic postganglionic fibres that are cholinergic, acting on M3 muscarinic receptors — the standing exception to the noradrenergic rule for sympathetic postganglionic neurons
- Secretion
- The coil produces an isotonic primary secretion driven by NKCC1; the duct then reabsorbs sodium through ENaC and chloride through CFTR without water, so sweat reaching the surface is hypotonic
- Capacity
- Up to 1-2 L/hour, and higher in the heat-acclimatised; acclimatisation also lowers sweat sodium concentration through increased aldosterone-driven ductal reabsorption
- Distribution
- Densest on palms, soles and forehead; present in palmoplantar skin where hair follicles are absent, so they are the only adnexal reservoir for healing there
When it goes wrong
Defective CFTR preventing ductal chloride reabsorption (cystic fibrosis)
Sweat chloride above 60 mmol/L on the pilocarpine iontophoresis sweat test (30-59 intermediate), and salt-loss crises with hyponatraemic dehydration and metabolic alkalosis in hot weather
Antimuscarinic drugs (atropine, tricyclic antidepressants, sedating antihistamines, oxybutynin) blocking M3 receptors
Anhidrosis with dry skin, heat intolerance and a risk of hyperthermia in the elderly during a heat wave
Excess cholinergic sudomotor output (primary focal hyperhidrosis)
Symmetrical palmar, plantar and axillary sweating; treated stepwise with topical aluminium chloride, iontophoresis, botulinum toxin (which blocks acetylcholine release) and rarely sympathectomy, with compensatory sweating a common complication
Practise this structure
No question in the bank is tagged to Eccrine sweat gland yet. Questions appear here automatically once one is — the question bank is free to browse in the meantime.