Question

The work of the heart can never be interrupted. The reason is that the heart’s job is to keep oxygen rich

blood flowing through the body. All the body’s cells need a constant supply of oxygen, especially those in

the brain. The brain cells live only for four to five minutes after their oxygen is cut off, and then brain death

occurs, leading to the entire body dying.

The heart is a specialised muscle that serves as a pump. This pump is divided into four chambers, two

called atria and two called ventricles, connected by tiny doors called valves. The chambers work to keep

the blood flowing round the body in a circle with a detour to the lungs to purify the blood by removing

carbon dioxide from it and adding oxygen to it.

At the end of each circuit, veins carry the blood to the right atrium, the first of the four chambers. Two-

fifths of the oxygen by then is used up and it is on its way back to the lungs to pick up a fresh supply and to

give up the carbon dioxide it has accumulated. From the right atrium the blood flows through the tricuspid

valve into the second chamber, the right ventricle. The right ventricle contracts when it is filled, pushing

the blood through the pulmonary artery, which leads to the lungs. In the lungs the blood gives up its

carbon dioxide and picks up fresh oxygen. Then it travels to the third chamber, the left atrium. When this

chamber is filled, it forces the blood through the mitral valve to the left ventricle. From here it is pushed

into a big blood vessel called aorta, the main artery, and sent round the body through the various arteries.

Heart disease can result from any damage to the heart muscle, the valves or the ‘natural pacemaker’ of the

heart. Electrical impulses from the heart muscle cause our heart to beat (contract). This electrical signal

begins in the Sino-atrial (SA) node, located at the top of the heart’s upper-right chamber (the right atrium).

The SA node is sometimes called the heart’s ‘natural pacemaker’.

If the muscle is damaged, the heart is unable to pump properly. If the valves are damaged blood cannot

flow normally and easily from one chamber to another, and if the pacemaker is defective, the contractions

of the chambers will become un-coordinated.

Until the twentieth century, few doctors dared to touch the heart. In 1953 all this changed. After twenty

years of work, Dr John Gibbon in the USA had developed a machine that could take over temporarily from

the heart and lungs. Blood could be routed through the machine, bypassing the heart so that surgeons

could work inside it and see what they were doing. The era of open heart surgery had begun.

In the operating theatre, it gives surgeons the chance to repair or replace a defective heart. Many parties

have had plastic valves inserted in their hearts when their own was faulty. Many people are being kept

alive with tiny battery operated pacemakers; none of these repairs could have been made without the

heart-lung machine. But valuable as it is to the surgeons, the heart-lung machine has certain limitations. It

can be used only for a few hours at a time because its pumping gradually damages the bloods cells.​

Answer 1

Answer:

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Explanation:

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