Why does the nurse have to find a vein to draw blood? What’s the difference between that and the blood that shows up if I had a cut on my arm?

Question

Deleted my other question, realized it was too vague and not relevant to my actual question.

In: Biology

Answer 1

The blood from a cut comes out when you cut many small blood vessels, letting the blood in them escape.

This blood is no different from the blood in a vein, but you damage lots of tissue to get it. Also the small damaged vessels tend to clot quickly, so large volumes are hard to get.

Nurses find a vein because they don’t want to damage large areas of tissue to get blood, and don’t want the bleed to clot before they get the blood they need, so they draw from a larger blood vessel (a vein).