Illustration of the cardiovascular and lymphatic systems, both are circulatory systems in the human body. The cardiovascular system is comprised of veins (blue) and arteries (red) that transport blood to and from the heart, allowing for gas exchange between the lungs and all other organs. The lymphatic system (green) aids in the drainage of excess fluid from tissues back into the blood, fat transport and immune responses. Both systems work to maintain cells with a supply of nutrients and to remove waste products, which is important for proper function.