Question

differentiate between Pulmonary artery and Pulmonary vein

Answer 1

Normally :

Artery - carry blood (oxygenated) from heart to body

Vein - carry blood (deoxygenated) from body to heart

In case of Pulmonary (meaning relating to Lungs) it is the opposite of normal.

Answer 2

An artery is defined as a blood vessel that carries blood away from the heart, and a veinas a blood vessel that carries blood towardthe heart.

In the pulmonary circuit, blood leaving the heart is on its way to the lungs to pick up oxygen, so blood in the pulmonary arteries is relatively low in oxygen. Blood in the pulmonary veins is on its way back from the lungs, so it is relatively high in oxygen.

This is opposite from the blood in arteries and veins in all the rest of the body, the systemic circuit. Systemic arterial blood is relatively high in oxygen because it hasn’t yet reached the organs where it unloads oxygen. After circulating through those organs, blood is on its way back to the heart in the systemic veins and is relatively low in oxygen.

In medical illustration, it has been traditional to show high-oxygen vessels in red and low-oxygen vessels in blue. Therefore we arrive at the color scheme somewhat confusing to beginning students:

systemic arteries in red
pulmonary arteries in blue
systemic veins in blue
systemic veins in red