What does heart do in human body?

          All the muscles and tissues that make up the body must be continually supplied with food and oxygen. This job is carried out by the blood circulatory system.

          The heart lies at the centre of the circulatory system and pumps the blood around the body. About the size of your fist, it is an incredibly strong organ, made entirely of muscle. It beats more than two billion times during the average life span of a person and pumps about 340 litres of blood every hour—enough to fill a car’s petrol tank every seven minutes.

          Blood containing fresh oxygen travels from the lungs to the heart through the pulmonary veins. At the same time, blood with very little oxygen left in it returns to the heart along veins from the muscles and tissues. The heart pumps the fresh blood to the rest of the body and the exhausted blood to the lungs. It pumps the blood at high pressure so that it can travel upwards to the head—against gravity—as well as downwards. You can feel this pumping action by placing your fingers on the inside of your wrist or the side of your neck, both points where a main artery lies close to the surface of your skin.

 

 

BLOOD

          Pumped by the heart, blood collects oxygen from the lungs and dissolved food from the liver and delivers it to all parts of the body. It also clears away waste, helps cool the body when it overheats, clots when the skin is damaged and protects against invading bacteria and viruses.

          The veins and arteries in your body look like a page in a road atlas. There are motorways, the main blood-carrying tubes or vessels, which lead out from the heart to the limbs and the head. There are also lanes and tracks, tiny vessels called capillaries that reach all the cells in the body.

 

 

          Blood is made up of millions of tiny cells floating in a yellowish, watery fluid called plasma. There are red cells, used for carrying oxygen, white cells, which fight any infection by invading bacteria or viruses, and platelets, which make the blood clot when a vessel is damaged, so sealing the wound. Different kinds of white cell work together to protect you from disease: T-cells, which identify invaders; B-cells, which make deadly proteins called antibodies that surround the invaders; and macrophages, which swallow them up and destroy them.

Picture Credit : Google