Heart is a Pump.
We shall take this topic, question and answerwise, to see how the heart is a pump and what enables it to work as a pump and perform its function to keep you alive.
Why is the Heart a Pump.
A pump is a mechanical device that uses pressure or suction to move fluids or gases in the forward direction. This definition of a pump fits the heart like a glove and defines exactly what the heart does.
How The Heart Pumps.
If you read function of heart|what does heart do, you will understand that the heart has the right side and the left side, each again separated into two chambers, each with an inlet and an outlet guarded by non return heart valves to force the blood in the forward direction. The heart therefore has four chambers which pump blood with the help of the cardiac muscle, the myocardium which forms the middle part of the heart wall.
Picture showing how the heart pumps blood.
The right side of the heart has the right atrium above and the right ventricle below with an atrioventricular opening in between guarded by the tricuspid valve. The deoxygenated blood from all parts of the body, containing carbon dioxide and metabolic wastes, is collected through a network of venules and veins, and brought to the inferior vena cava (from the lower side of the body) and the superior vena cava (from the upper part of the body). These large veins of the heart empty this blood into the right atrium which pushes or pumps this blood through the tricuspid valve into the right ventricle.
The right ventricle contracts and pumps this blood with pressure through the pulmonary valve into the pulmonary artery which carries this deoxygenated blood to the lungs for purification. In the lungs there is exchange of gases between this blood which contains carbon dioxide and the inhaled air which contains oxygen.
Carbon dioxide from this impure blood is released into the inhaled air in the lungs and oxygen from the air is taken up by the blood. The inhaled air which now contains carbon dioxide and less of oxygen is exhaled. The blood which now contains oxygen is carried by the pulmonary veins to the left side of the heart.
The Left Side of the Heart has the left atrium as the upper chamber, which receives the oxygenated blood from the four pulmonary veins (two from each lung). When full, it pumps this blood through the left atrioventricular valve, the mitral valve, into the left ventricle.
When full, the left ventricle pumps this blood with a greater pressure through the aortic valve into the aorta, which is the main artery of the body. This blood is carried to all parts of the body through a network of arteries, arterioles and capillaries. As this network is large, the left ventricle pumps with a greater pressure than the right ventricle, which has to pump the blood only to the lungs. Read blood flow in heart for more details.
The Pumping Heart.
The pumping heart pushes this blood normally between 60 to 90 times a minute. Each time the output of the pumping heart chambers is about 70 ml of blood and the total blood which is about 5 liters is circulated in one minute. Read cardiac cycle for details.
The heart can only be described as a miracle creation, considering that the heart beats (contracts and relaxes) about 72 times per minute continuously, 24×7, for all the years that you live, without a pause, by generating its own electric impulse. Reading fascinating heart facts will give a better insight into the heart’s “greatness”.
The myocardium, which is the middle layer of the heart wall, is muscular in nature and is an involuntary muscle not in our voluntary control. This cardiac muscle is resistant to fatigue by virtue of its unique nature and composition and this enables the heart to pump blood continuously throughout life in the same synchronized sequence and fashion. The myocardium is responsible for the pumping action of the heart.
What Makes the Heart Work.
Every pump requires fuel or electricity to pump. The heart is no exception, but the remarkable difference here is that, the heart generates its own electricity. It has a sinoatrial node (SA node) in the right atrium which is made of specialized cells which generate the heart’s own electric impulse.
This impulse travels throughout the heart’s wall via the AV node , the bundle of His, purkinje fibers, the bundle branches, all of which constitute the electric circuit of the heart.
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