NCERT Solution for Class 10 Science Chapter 6
Life Processes
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Exercises Questions
Page No-113
Questions No-11
Describe double circulation of blood in human beings. Why is it necessary?
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In double circulation there is complete segregation of oxygenated and deoxygenated blood. Because of this the blood passes twice through the heart in one cycle of circulation hence the name double circulation.
This is necessary for optimum oxygen utilization as humans are warm blooded animals and need extra energy to maintain their body temperature.
In our heart blood enters twice and also pumped out twice from the heart. The deoxygenated blood from the body is brought to the right atrium through vena cava from where it is sent to right ventricle. From right ventricle, the blood is pumped to the lungs for oxygenation through pulmonary artery. The oxygenated blood from lungs again enters the left atrium of the heart through pulmonary veins. From left atrium it is send to left ventricle, from where this oxygenated blood is pumped to different parts of body through the arteries. In this way the blood flows through the heart twice, that’s why it is called ‘double circulation’.
Necessity of double circulation: The right side and the left side of the human heart are useful to keep deoxygenated and oxygenated blood from mixing. This type of separation of oxygenated and deoxygenated blood ensures a highly efficient supply of oxygen to the body. This is useful in case of humans who constantly need energy to maintain their body temperature.
Because both oxygen and carbon dioxide have to be transported by the blood, the heart has different chambers to prevent the oxygen-rich blood from mixing with the blood containing carbon dioxide. The human heart is divided into four chambers − the right atrium, the right ventricle, the left atrium and the left ventricle.
Oxygen-rich blood from the lungs comes to the thin-walled upper chamber of the heart on the left, the left atrium. The left atrium relaxes when it is collecting this blood. It then contracts, while the next chamber, the left ventricle, expands, so that the blood is transferred to it. When the muscular left ventricle contracts in its turn, the blood is pumped out to the body.
De-oxygenated blood comes from the body to the upper chamber on the right, the right atrium, as it expands. As the right atrium contracts, the corresponding lower chamber, the right ventricle, dilates. This transfers blood to the right ventricle, which in turn pumps it to the lungs for oxygenation.
During this process blood goes twice through the heart. That’s why it is known as double circulation.
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