Answer:
human heart is like a machine which pumps the blood to various parts of the body.it has 4 chambers.right atrium.right ventricle,left atrium and left ventricle.during the entire life span of man,heart carries on its activity continuously,even when we are asleep.this is done by specialised cardiac cells.the blood from whole of the body is collected in the superior and inferior venacava,and brought to the right atrium.now blood moves to right venticle through the tricuspid valve.from the right ventricle it goes to the lungs.her deoxygenated blood is removed by the process of expiration,and oxygen is added to the blood.this takes place through difference of partial pressures.now oxygenated blood returns to heart in the left atrium.it now moves to the left ventricle through a bicuspid or mitral valve.once ot reaches left ventricle,it is pumped to whole of the body -systemic circulation,through the aorta.
blood vessels are channels in which the blood is contained.ther are arteries which contain oxygenated blood,and veins contain deoxygenated blood.capillaries are the place where the gaseous exchange takes place.aorta divides into arteries,they divide into arterioles.venacava is forms by veins,they are formed of venules.