The blood vessel that carries pure blood is the Pulmonary Vein.

The circulatory system consists of a complex network of blood vessels that transport blood throughout the body. These blood vessels can be broadly categorized into three types: arteries, veins, and capillaries. While arteries carry oxygenated blood away from the heart, and veins transport deoxygenated blood towards the heart, there is one exception to this rule – the pulmonary veins.

What are the pulmonary veins?
The pulmonary veins are a set of four blood vessels that carry oxygenated blood from the lungs back to the heart. They are the only veins in the body that carry oxygen-rich blood, making them unique among the other veins.

Function of the pulmonary veins:
The main function of the pulmonary veins is to transport freshly oxygenated blood from the lungs to the heart. After the process of respiration, where oxygen is inhaled and carbon dioxide is exhaled, the oxygen molecules bind to red blood cells in the lungs. These oxygenated red blood cells then enter the pulmonary veins, which carry them back to the heart.

Pathway of the pulmonary veins:
1. Oxygenated blood: The pulmonary veins start in the capillary beds of the lungs, where the exchange of oxygen and carbon dioxide takes place. The oxygen molecules diffuse into the bloodstream and bind with the red blood cells, turning them into oxygenated blood.

2. Collection: The oxygenated blood is collected by the small pulmonary veins in the lungs.

3. Merge: The small pulmonary veins merge together to form two larger pulmonary veins – the right and left pulmonary veins.

4. Entry into the heart: The right and left pulmonary veins enter the left atrium of the heart, which is responsible for pumping the blood to the rest of the body.

5. Mixing of blood: In the left atrium, the oxygenated blood from the pulmonary veins mixes with a small amount of deoxygenated blood returning from the pulmonary artery.

6. Pumping to the body: The left atrium contracts, pushing the oxygenated blood into the left ventricle. From there, it is pumped out to the rest of the body through the aorta.

Conclusion:
In summary, the pulmonary veins are the blood vessels that carry pure, oxygenated blood from the lungs back to the heart. Unlike other veins in the body that carry deoxygenated blood, the pulmonary veins play a crucial role in ensuring the delivery of oxygen to different organs and tissues, thus supporting the overall functioning of the body.