Overview

Apocrine glands have a wide-lumened secretory coil in the deep dermis or hypodermis, lined by a single layer of eosinophilic cuboidal-to-columnar cells with apical cytoplasmic "snouts", surrounded by myoepithelial cells. The straight duct opens into the hair follicle infundibulum, above the entry of the sebaceous duct. Although named for apparent decapitation (apocrine) secretion, they also secrete by merocrine exocytosis.

They develop with hair follicles but remain small until puberty, when androgens make them functional. The secretion is odourless when produced — a viscous, milky fluid containing proteins, lipids, steroids and carbohydrates — but cutaneous bacteria (Corynebacterium, Staphylococcus) metabolise it into volatile, odorous compounds. Control is by sympathetic adrenergic fibres and circulating catecholamines, so secretion increases with emotional stress (pain, fear, sexual arousal) rather than with heat. A variant of the ABCC11 gene common in East Asia reduces apocrine secretion, producing little axillary odour and dry earwax.

Location: Axillae, areolae and nipples, perianal region, mons pubis, labia majora and scrotum; modified forms in the external ear canal (ceruminous) and eyelids (Moll).

Anatomy

Innervation: Sympathetic adrenergic fibres; also stimulated by circulating adrenaline.
Histology: Large lumen; tall eosinophilic secretory cells with apical blebs; prominent myoepithelial layer; duct opens into a hair follicle.
Development: Bud from the wall of the hair follicle (like sebaceous glands); remain quiescent until puberty.

Function

Secretion of odour precursors — chemical and social signalling
Contribution to the surface lipid film in hair-bearing regions

Secretions: Viscous, protein- and lipid-rich secretion with steroids and ammonia precursors; odour results from bacterial metabolism.

Clinical significance

Hidradenitis suppurativa

Chronic inflammatory disease of apocrine-bearing skin (axillae, groin, buttocks) starting with follicular occlusion: painful nodules, abscesses, sinus tracts and scarring; associated with smoking and obesity.

Bromhidrosis and Fox–Fordyce disease

Bromhidrosis is offensive body odour from bacterial breakdown of apocrine sweat. Fox–Fordyce disease is itchy papules from apocrine duct obstruction in the axillae of young women.

Extramammary Paget disease

Intraepidermal adenocarcinoma in apocrine-rich skin (vulva, perianal, scrotal) presenting as a persistent red, eczema-like plaque; may signal an underlying adnexal or visceral cancer.

Test yourself

Which statement about apocrine sweat glands is correct?

They are found over the whole body surface
They open directly onto the skin surface via a spiral duct
They open into hair follicles and become active at puberty
They are the main glands for thermoregulatory sweating

Answer: They open into hair follicles and become active at puberty

Apocrine glands are restricted to the axillae, areolae and anogenital region, empty into hair follicles above the sebaceous duct, become active at puberty under androgens and produce a protein-rich secretion that bacteria convert into body odour.