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Skin
Gray's Anatomy (1918) plate, public domain
The skin is the body's largest organ — about 2 square metres and several kilograms in an adult — forming the barrier between you and the world. Its outer epidermis renews constantly and produces the pigment melanin; the dermis beneath gives strength and elasticity with collagen, and houses vessels, nerves, glands and hair roots; below lies subcutaneous fat for insulation and cushioning. Skin regulates temperature, senses touch, makes vitamin D and mounts immune defences.
Key facts
- You shed roughly a million dead skin cells a day; the epidermis fully renews about every month.
- Skin thickness varies from about 0.5 mm on the eyelids to 4 mm or more on the soles.
- Its blood vessels constrict in cold and dilate in heat, making skin a radiator under nervous control.
- The fingerprints' ridges improve grip and are unique to each person, even identical twins.
What can go wrong
Skin problems are the commonest reason for GP visits: eczema and dermatitis from barrier failure and allergy, acne from blocked oil glands, infections from bacteria, viruses and fungi, and growths — mostly benign, but including skin cancers driven mainly by ultraviolet exposure. Any new, changing, bleeding or non-healing spot should be examined; mole changes are assessed with dermatoscopy (a magnifier) and biopsy if needed.
Related conditions
Related procedures & tests
Related symptoms
Watch: related videos
Frequently asked questions
Why does skin wrinkle with age?
Sun exposure and ageing break down the dermis's collagen and elastin while fat thins beneath, so the surface loses support and elasticity and folds persist.
Does skin really breathe?
Only negligibly — nearly all gas exchange happens in the lungs; the skin's key respiratory role is temperature control through sweat and blood flow, not oxygen uptake.
Educational information only. This atlas explains normal anatomy and describes conditions in general terms; it is not medical advice and does not replace assessment by a qualified clinician. If you have symptoms that worry you, seek medical care.
