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ELI5 Yahaaa

More than a wrapper

What Does Your Skin Do?

Skin is a barrier, a thermostat, a sense organ and a self-repairing surface.

Barrier against germsand water lossTemperature controlTouch sensingConstant self-repair
Your largest organ, doing four jobs.
  1. Step 1 of 5

    It is your largest organ.

    Skinabout 2 m²,several kgLiverthe largestinternal organ

    Around two square metres and several kilograms. It is a working organ, not simply a covering.

  2. Step 2 of 5

    The barrier is made of dead cells.

    Outer layer — dead,waterproof cellsthe actualbarrierLiving layer — dividingcellsconstantlymakingreplacementsDeeper layer — nerves,vessels, glandsthe workingmachinery

    The outer layer is flattened dead cells packed with a waterproof protein. Being dead is the point — it can be worn away without harm.

  3. Step 3 of 5

    It is replaced continuously.

    New cells made below Pushed upward,dying Shed from thesurfaceAbout amonth

    You shed millions of cells a day and grow a completely new outer layer roughly every month. Most household dust is old skin.

  4. Step 4 of 5

    It controls your temperature.

    Too hot Vessels widen, sweatstartsToo cold Vessels narrow, heatconserved

    Blood vessels widen to dump heat and narrow to keep it in. Sweat glands add evaporative cooling when that is not enough.

  5. Step 5 of 5

    It repairs itself.

    1 A cut2+Clot, clean,rebuild3 Healed,sometimesscarred

    A cut triggers clotting, then cleanup, then new tissue. Deep damage leaves a scar — repaired with strong but less organised tissue.

    Skin colour comes from melanin, which absorbs ultraviolet and protects the dividing cells beneath from damage.

The short version

Skin is a self-replacing barrier that also controls temperature, senses touch and repairs its own damage.

Try it yourself

Pinch the back of your hand and let go. How fast it springs back reflects hydration and the elastic fibres inside.

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