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What Is the Difference Between Arteries and Veins?

Almost every artery sends oxygenated red blood cells to areas of the body.
Blood is typically drawn from a vein, rather than an artery, for a blood test.
A diagram of the human head and neck, including the arteries in red.
Arteries and veins are key components of the circulatory system.
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  • Written By: Adam Hill
  • Edited By: Bronwyn Harris
  • Last Modified Date: 18 December 2014
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Arteries and veins are the parts of the circulatory system which carry blood between the heart, lungs, and all other areas of the body. While they both carry blood, they do not have much else in common. Arteries and veins are made of somewhat different tissue, each performing certain functions in a specialized way. The first and most important difference between the two is that all arteries carry blood away from the heart, and all veins carry blood to the heart from outlying areas. Most arteries carry oxygenated blood, and most veins carry deoxygenated blood; the pulmonary arteries and veins are the exceptions to this rule.

Arterial tissue is designed and specialized in a way to make it particularly suited to the quick and efficient delivery of blood, which carries the oxygen essential for the functioning of every bodily cell. The outer layer of an artery is made of connective tissue, which covers the muscular middle layer. These muscles contract between heartbeats in such a reliable way that when we take our pulse, we are not actually feeling our heartbeat per se, but arterial muscle contraction instead.

Beyond the arterial muscle is the innermost layer, made of smooth endothelial cells. These cells are specialized to provide a smooth pathway for blood to flow through. This area of cells is also what can become damaged and compromised over a person's lifetime, leading to two common causes of death, namely heart attack and stroke.

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Veins have a different structure and function from arteries. They are very flexible, and collapse when they are not filled with blood. They usually carry deoxygenated blood, rich in carbon dioxide, to the heart so that it can be sent to the lungs for oxygenation. The layers of vein tissue are similar in some ways to those of arteries, although the muscle does not contract like arterial muscle does.

Unlike other arteries, the pulmonary artery carries deoxygenated blood. Once the veins have brought this blood from the body to the heart, it is pumped to the lungs. The pulmonary vein moves the oxygenated blood from the lungs back to the heart.

While the location of arteries is very similar from person to person, this is not so much the case with veins, which have greater variability. Veins, unlike arteries, are used as access points to the bloodstream in the medical field, such as when a person receives medicine or fluids directly into the bloodstream, or when blood is drawn. Because veins do not contract as arteries do, there are valves present in veins which keep blood flow going in one direction only. Without these valves, gravity would quickly cause blood to pool in the extremities, causing injury or at the very least impairing the system's efficiency.

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anon342874
Post 36

How do you avoid hitting an artery when taking blood?

anon339360
Post 35

I am a phlebotomist. We know where to 'stick the needle' because we feel for the veins. We don't just randomly stab based on where we think it should be according to our knowledge of anatomy because it does vary widely for each person. As for why the veins hold the blood after death but the arteries do not, it is because the veins have valves.

After death, the heart pumps all of the blood out of the arteries and the body exsanguinates. But the valves in the veins prevent the blood from bleeding out of the veins. I have had the unfortunate job of drawing someone after death before and I assure you the veins do in fact hold the blood in.

anon337451
Post 34

What are the six arteries and six veins?

anon329086
Post 32

I helped my boyfriend when he took his Phlebotomy test. They know where most veins are because the ones they need to draw from or inject into are typically visible from the surface or are found within the same half a centimeter of space on most humans. They only will use certain parts or the body where they can be reasonably sure of the locations because some people will pass out if they are stuck by a needle too many times (then again, once is sometimes too many) and it's unprofessional and scarring to puncture the skin too much.

anon274878
Post 27

I want to know why, even after our death, our veins contain blood but our arteries don't?

anon160769
Post 21

veins vary from person to person, due to race, gender and other things, but vary in thickness because different blood pressures need different wall thickness and some are deeper beneath the skin than others.

as for needles, I'm not exactly sure. but i think there are certain spots that all veins go through and even if they misplaced it, it probably would just soak it up. Note: I'm not a doctor or anything but these are my thoughts.

anon147022
Post 19

What I don't understand is, why do you say that if veins vary from person to person, how do nurses always know the spot where to inject the needle?

Another thing, if veins flow towards the lungs and back to the heart, why do you call them access points. Shouldn't they flow to extremities then?

anon138073
Post 15

this really helped me in biology.

anon115089
Post 11

This article was very helpful. Thank you.

anon85011
Post 9

this article is a big help. thanks!

anon82038
Post 7

Thank you very much for this article.

anon77251
Post 6

why are capillaries are so important?

anon68395
Post 5

thanks. that was a lot of help!

anon48726
Post 1

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