Question 11: Describe double circulation of blood in human beings. Why is it necessary?
Answer:
Mammals like human beings, monkeys etc. have a double circulatory system and they include four chambered hearts (two auricles and two ventricles). Heart’s internal structure consists of auricles, ventricles, blood vessels, apertures and valves (contains various parts). As the blood passes through the heart twice during one cycle, this is known as double circulation of blood. Auricles act as the collecting chamber for the blood returning to the heart. They have to force the blood into the ventricles because of the thin wall of auricles; and ventricles act as the distributing chambers of the blood reaching the atria. Process of double circulation involves two parts – pulmonary and systemic circulation.
In pulmonary circulation, the exchange of blood takes place between heart and lungs. The deoxygenated blood from the right ventricle is pumped into the lungs through the pulmonary artery and from lungs oxygenated blood goes to the left auricle through the pulmonary vein; and from the left auricle the blood is pumped into the left ventricle.
In systemic circulation, the exchange of blood takes place between heart and body. The oxygenated blood from left ventricle is pumped into the aorta for further transportation of blood in the body and the deoxygenated blood from the body enters the right auricle through vena cava; and from right auricle the blood is pumped into the right ventricle of the heart by the body tissues.
Both pulmonary circulation and systemic circulation take place simultaneously.
This double circulation is necessary for the regulation and the maintenance of the body temperature.
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