The document summarizes the components and function of blood and blood vessels. It describes that arteries carry oxygen-rich blood away from the heart to capillaries, which connect to veins to return deoxygenated blood back to the heart. The inner walls of arteries are smooth to allow blood flow, while artery walls are muscular to aid pumping. Capillaries are thin and where gas exchange occurs. Veins are less strong than arteries as they transport lower-pressure blood. Blood carries oxygen, nutrients, hormones, antibodies and waste, helps regulate temperature, and forms clots to stop bleeding. Its components are plasma, red and white blood cells, and platelets.