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 The heart is a conical structure which lies slightly left in the chest or thoracic cavity. It's anterior end is broader while posterior end is narrower in shape . It is the size of one's fist. It is covered by two membranes called pericardial membranes. The space between these pericardial membranes is filled with a fluid called pericardial fluid which protects the heart from shocks. Internally heart is ...