eli5. How come you don’t continue to bleed from the hole in your vein after you get your blood drawn?

Question

eli5. How come you don’t continue to bleed from the hole in your vein after you get your blood drawn?

In: Biology

Answer 1

Because bleeding to death is bad. At one point in ancient time, animals developed repair systems to fix holes poked in them. Animals with that trait survived much better than those without. As a result, we all have the ability to repair small holes. There are things you can do to improve the repair effectiveness, like putting pressure on the hole, which we call “first aid”.