THE CIRCULATORY SYSTEM
The circulatory system or the transport system consists of heart, blood and blood vessels. The heart is the main pumping organ of a body which functions continously without stopping for a second. It is made of cardiac muscle whose contraction and relaxation makes a pulse rate or a heart beat . Blood is a red colour fluid freely floating in our body to supply food, nutrients and oxygen to each and every cell and also collecting waste materials from them . Blood vessels are the closed tubes through which the blood is circulated in our body. Structure of heart