Human body

Skin

Anatomy · Integumentary system

Why do you sweat when you are hot and get goose bumps when you are cold?

Your skin is your largest organ: a waterproof wall on the outside, a tough, stretchy layer underneath, and a cushion of fat below that. It also works as your body’s thermostat, sweating and sending more blood to the surface to lose heat, and squeezing vessels shut to keep heat in. It is packed with sensors for touch, vibration, heat and pain.

Skin is a layered organ: a self-renewing keratinised epidermis sits on a vascular, collagen-rich dermis, which rests on the fatty hypodermis. Its appendages, vessels and receptors make it a barrier, a thermoregulator and a sense organ, adjusting sweat, blood flow and hair position to keep core temperature near 37 °C.

Key facts

Area (adult)

≈ 1.5–2 m²

Mass

≈ 4–5 kg excluding hypodermis (≈ 7% of body mass)

Epidermal thickness

≈ 0.05–0.1 mm (thin skin) to ≈ 1.5 mm (palms, soles)

Dermal thickness

≈ 1–4 mm

Epidermal turnover

≈ 4 weeks from basal layer to shedding

Eccrine sweat glands

≈ 2–4 million; up to ≈ 1–2 L/h of sweat in heat

Parts you can explore (16)

• Stratum corneum
• Stratum granulosum
• Stratum spinosum
• Stratum basale
• Papillary dermis
• Reticular dermis
• Hypodermis
• Hair follicle
• Sebaceous gland
• Arrector pili
• Sweat gland & duct
• Blood vessels
• Melanocytes
• Meissner corpuscles
• Pacinian corpuscle
• Free nerve endings

In the 3D model

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Open Skin in 3D →

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