Human blood cells and blood vessels

Blood contains blood cells suspended in a fluid called plasma. Red blood cells transport oxygen, and have a structure adapted to carry as much oxygen as possible. Plasma transports water, glucose and other nutrients, and waste products including carbon dioxide and urea. Arteries carry blood away from the heart; capillaries carry blood to/from cells; veins carry blood back to the heart. Arteries, capillaries and veins have structures adapted to their functions, including different vessel walls and valves.