The heart is a muscular organ divided into four chambers: the right atrium, right ventricle, left atrium, and left ventricle. It is responsible for pumping blood throughout the body.
Arteries, veins, and capillaries make up the blood vessel system, playing crucial roles in transporting blood and facilitating gas exchange with tissues.
Blood consists of plasma, red blood cells, white blood cells, and platelets. It carries nutrients, oxygen, and waste products to and from the body's tissues.