How the Body Works: The Functions of Blood

Blood transports many different materials around the body. Red blood cells carry oxygen from the lungs to the tissues and carbon dioxide from the tissue to the lungs. Blood plasma transports antibodies, which protect the body from infection, carries food substances absorbed from the intestines and takes waste products to the kidneys for excretion. It also transports hormones, secreted by endocrine glands, to their sites of action. Clotting factors circulating in the plasma prevent blood loss whenever blood vessels are damaged or broken. Blood also regulates the water content of tissue cells. Blood buffers, chemicals within the blood, maintain the correct acidity of body fluids. Enzymes may be transported by blood plasma, which also distributes the heat produced by metabolism.