When the doctor/nurse takes blood from you, why do they try to find a vein, not an artery? And also why is this mainly done on the arm as opposed to other parts of the body?
In: Biology
We try to find a vein instead of an artery because the pressure of the blood in a vein is much lower than the pressure of the blood in an artery. This is important because the higher pressure in your arteries makes it much harder for your body to plug up the hole from the needle- you would bleed a lot more than if we poked a hole in a vein. The pressure is higher in arteries because the heart is a very strong muscle pushing the blood through the arteries to be taken all over the body. The pressure is lower in veins because little muscles all over your body are (more) gently pushing the blood through the veins back to your heart to get pumped out all over again.
Sometimes we do take blood from arteries! There are certain tests that we can only run on blood from arteries. The blood inside your veins and arteries is pretty similar, but arterial blood can tell us extra information about things like your lungs and kidneys, and how acidic your blood is. Thankfully, most tests can be run on blood from veins. When we do have to take blood from an artery, we use as small a needle as possible and hold pressure on the spot we stuck with our hand or a bandage for a much longer time. This helps the body make a plug for the hole.
We mostly take blood from the arms because they are easy to get to and usually the veins are pretty big and easy to find. However, we can take it from anywhere! I’ve taken blood from feet, stomachs, breasts, and necks when we couldn’t find a vein in an arm. We are extra careful to not take blood from people with diabetes in their legs or feet because diabetics don’t have very good blood flow in their legs, so the hole may not heal.
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