Skin Thermoregulation: How Your Body Maintains Temperature

The skin is the primary effector organ for thermoregulation, integrating vascular, sudomotor, and pilomotor responses.

Mechanisms

1. Vasodilation / Vasoconstriction: Cutaneous vessels expand (heat loss) or constrict (heat conservation) via sympathetic control.
2. Sweating & Evaporation: Eccrine glands secrete hypotonic sweat; evaporation removes ~0.58 kcal/g water. Most effective in dry heat.
3. Radiation: Skin emits infrared; net loss when environment cooler.
4. Pilomotor Response: Arrector pili muscles contract → hair erection (goosebumps) trapping air layer (minimal in humans).
5. Countercurrent Heat Exchange: Deep arteries/veins in limbs transfer heat, preserving core temperature.

Hypothalamic Control

Preoptic area integrates core/skin thermoreceptor input → orchestrates autonomic & behavioral responses (seeking shade/clothing).

Clinical Relevance

• Impaired in burns (loss of barrier/sweating), spinal cord injury (autonomic dysreflexia), anhidrosis, antihypertensives, anticholinergics.
• Heat stroke = thermoregulatory failure; medical emergency.