Sebaceous & Sweat Glands: Structure, Function & Clinical Relevance

Both gland types reside in the dermis and are essential for skin homeostasis, but they differ in secretion, regulation, and distribution.

Sebaceous Glands

• Location: Derma, usually attached to hair follicles (pilosebaceous units); absent on palms/soles.
• Secretion: Sebum—lipid mixture (triglycerides, wax esters, squalene, cholesterol).
• Functions: Lubricates skin/hair; waterproofs stratum corneum; antimicrobial (free fatty acids, low pH); transports antioxidants (vitamin E).
• Regulation: Androgen-driven (testosterone, DHT); peaks at puberty; increases with stress.
• Disorders: Acne (hypersecretion + follicular plugging), seborrheic dermatitis, sebaceous hyperplasia, steatocystoma.

Sweat Glands

Eccrine (Merocrine)

• Distribution: Nearly entire body (3–4 million); highest on palms, soles, forehead.
• Secretion: Hypotonic fluid (99% water + NaCl, KCl, lactate, urea, antimicrobial peptides).
• Function: Thermoregulation (evaporative cooling); minor excretory role.
• Control: Sympathetic cholinergic (acetylcholine); activated by heat, exercise, emotion.

Apocrine

• Distribution: Axillae, anogenital, areola, external auditory canal; develop at puberty.
• Secretion: Milky, protein/lipid-rich; odorless until bacterial metabolism.
• Function: Pheromonal signaling (vestigial in humans); stress-induced.
• Control: Sympathetic adrenergic.

Clinical Pearl

Anhidrosis (absent sweating) → heat stroke risk. Hyperhidrosis → quality-of-life impact. Sebum composition changes inform acne/seborrhea management.