what does the water inside the jar represent

The water inside the jar represents the blood in the circulatory system. In the heart pump model, the jar of water is filled to represent the heart pumping blood to various body parts. The straws in the jar represent the veins and arteries, and the pan represents the other body parts where the blood is distributed. The balloon pumps the water into the straw and into the jar, then to the pan. In a similar manner, the heart pumps the blood through the arteries to various parts of the body.