What pulmonary blood vessel carries oxygen-rich blood?
The heart pumps blood. The left side of the heart collects oxygen-rich blood from the lungs and distributes it through the aorta. The aorta by branching into the arteries supplies the whole body with oxygen-rich blood.
The right side of the heart collects oxygen-poor blood from the whole body and sends it to the lungs through the Pulmonary arteries . When we breathe, the lungs give oxygen to this oxygen-poor blood and take out the carbon-dioxide. And we breathe out this carbon-dioxide.
Thus the lungs take in oxygen-poor blood, enrich it with oxygen, and send it back to the heart.
The lungs convey this oxygen-rich blood to the heart via the Pulmonary veins.
This picture shows the pulmonary veins (yellow arrows) entering the heart. The red colour denotes oxygen-rich blood. The blue colour denotes oxygen-poor blood.