Explain that this is not a perfect model. Here we have only one artery leading to one capillary leading to one vein. In the human body, the arteries branch off ever smaller until they get to the network of capillaries. In addition to oxygen, blood also carries nutrients to the body cells. The villi, tiny finger-like parts lining the small intestine, absorb nutrients from digested food.
Blood picks up the nutrients from the villi.
Eventually, the body cells absorb the nutrients out of the blood. Along with oxygen and nutrients, blood carries hormones and antibodies to different parts of the body. Blood consists of blood cells, platelets, and plasma. Red blood cells are responsible for carrying oxygen to the rest of the body. White blood cells help to fight infection.