In plants, there is vascular tissue or conducting tissue located in its veins. Inside, there are xylem cells that conduct water and minerals upward from roots to leaves and phloem that conducts food from leaves downward to all parts of the plant. This resembles a circulatory system as it is a way for materials to travel throughout a plant. However, there is no heart or pump to assist circulation--water moves up a plant against gravity by capillary action. The human circulatory system has a pump called the heart, which has four chambers. The right side is responsible for pumping blood to the lungs to gain oxygen and release carbon dioxide. The left side is responsible for pumping oxygenated blood throughout the body. Arteries carry blood away from the heart and contain muscle that contracts as the heart beats. This pushes the blood along the circulatory pathway. Tiny capillaries allow the diffusion of materials between the bloodstream and cells and vica versa. Veins carry returning blood back to the heart again, and valves keep the blood flowing in the correct direction. Plants not only lack a heart to pump materials throughout its structure, they also lack muscle tissue. Their conducting tissue is like the pipes in a house or a drinking straw serving as a way to support and transport materials insde the plant.