The familiar red vital fluid in the body that contains white and red cells, platelets, proteins, and other elements: Blood is transported throughout the body by the circulatory system.

Blood functions in two directions: arterial and venous. Arterial blood is the means by which oxygen and nutrients are transported to body tissues while venous blood is the means by which carbon dioxide and metabolic by-products are transported to the lungs and kidneys respectively for removal from the body.