When they draw blood, how does the vein not stay punctured after the needle is taken out



They just shoved a spiky needle in your vein, how come the blood still stays inside your veins after the needle is taken out, is there no hole in the middle of your vein?

In: Biology

Blood does come out, just not at the same rate it went into the vial. This is because the vial is under negative pressure so it pulls the blood in. Additionally, Veins are under low pressure and are stetchy so that hole close somewhat so you bleed minimally, then you clot to close it the rest of the way.

Blood vanes and skin are elastic so the needle will push most of it aside and then it closes up after you withdraw the needle. So even a big needle will only leave a small hole. And that hole will quickly get filled up with blood that coagulates sealing it all up. So while there may be a tiny bit of blood loss, for which you do get a band aid, it will quickly close itself in seconds and heal in the matter of hours.

It’s a really small hole.

The skin and vein material are both elastic, and fat and muscle around it push back together, so mostly start to close as soon as the needle is removed.

Materials go in or out because of pressure (negative to draw out positive to inject).

When you blood hits either the damaged, not smooth, wall it starts to clot, closing up the wound.

Your blood pressure is only about 1.5 to 3 psi, so not much would come spurting out of an open hole to begin with(contrary to many movies)

I hope my input is within the subject range but, coming from having mutiple blood tests done, some nurses aren’t really careful (due to racism against the minority) and some miss their shot and can tear the tissue, this can cause the senstive tissue to break often and bruise easily in the future.