I'm learning anatomy. What I learnt is that we have arteries that have oxygenated blood which appears red in color, and branch blood to arterioles to deliver blood to cells via capillaries from where de-oxygeneated blood is collected via venules into veins to go back for oxygenation. So:

artery = oxygenated

vein = de-oxygenated

However, in defining the pulmonary vein and pulmonary artery, I see the reverse of these definitions.

The pulmonary artery is for de-oxygenated blood.

Why is it so?

  • 5
    $\begingroup$ Ask youself, what function is served by pulmonary circulation? What function is served by systemic circulation? What part of the anatomy connects the two? $\endgroup$
    – MikeyC
    Aug 4, 2020 at 15:49

1 Answer 1


It is true that nearly all arteries carry oxygenated blood and nearly all veins carry de-oxygenated blood, but that is not what defines them. Arteries are blood vessels that carry blood away from the heart, and veins carry blood towards the heart. If you look at the situation in that light, the naming makes sense: the pulmonary artery is carrying de-oxygenated blood away from the heart to the lungs, and the pulmonary vein is carrying the re-oxygenated blood back to the heart, to be pumped through the rest of the body.

  • $\begingroup$ Although these complicate classification. $\endgroup$
    – J.G.
    Aug 6, 2020 at 19:11

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