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?