Why does blood from the body need to be pumped through lungs before it is back body?

The blood from the body needs to be pumped through the lungs before it is back to the body because of gas exchange. In the lungs, the blood releases carbon dioxide, a waste product of cellular respiration, and takes up oxygen, which is essential for cellular respiration. This gas exchange process is necessary to maintain the proper balance of oxygen and carbon dioxide in the body.

The blood is pumped from the heart to the lungs through the pulmonary arteries. In the lungs, the blood vessels are very thin and allow for the easy diffusion of gases between the blood and the air in the lungs. The carbon dioxide in the blood diffuses out into the air, and the oxygen in the air diffuses into the blood.

The oxygenated blood then returns to the heart through the pulmonary veins. From the heart, the oxygenated blood is pumped out to the rest of the body through the aorta, the largest artery in the body.