Why does hitting someone (or getting hit) hard causes a bruise? Why is it blue?
In: Biology
A sufficiently powerful impact will cause tissue and capilaries to break meaning you have a hematoma which is localized bleeding under the skin.
Now for some reason some blood vessels like Veins will look blue or purple through the skin, but thats because blood carrying CO2 is darker then the bright red of blood carrying O2.
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