HSEB Notes on Course of Circulation | Zoology, Biology Class 12

Biology | Zoology
HSEB Notes on Course of circulation 

Class : 12

Course of circulation 

1. Pulmonary Circulation 

It is the circulation between the heart and lungs. The impure blood(deoxygenated blood) is pumped out from the right ventricle. The pulmonary trunk takes the impure blood. The pulmonary trunk divides into two pulmonary arteries. The pulmonary arteries supply impure blood to the two lungs. In side the lungs, the impure blood is purified. After the purification, the pure blood is returned to the heart through the pulmonary veins. The pulmonary veins open into the left atrium.

2. Systemic circulation

It is the circulation of blood from heart to the whole body except the lungs. In this circulation, the pure blood is pumped from the left ventricle. The aortic arch divides into many arteries carrying pure blood to the different organs and regions of body. In the tissues, the capillary net works allow the exchange of gases and nutrients. The deoxygenated blood is then returned back through venules and veins. The impure blood is returned to right atrium through inferior and superior venacavae.

2.a. Portal circulation 

it is the special arrangement of veins. In this, the certain veins instead of carrying blood directly to the heart, enter into the another organ. In this case the second set of capillaries is formed. This formation of second set of capillaries is called portal system. The veins coming from the alimentary especially from the intestine and stomach contains glucose rich blood. Such blood is carried to the liver first. In the liver, the excess glucose is stored. After this the blood is carried to the heart. 

2.b. cororary circulation 

it is the circulation of pure blood from the heart to the muscles of the heart. The coronary arteries take pure blood to the muscles of the heart and the coronary veins return the impure blood from the muscles of the heart to the heart through the superior venacava. This circulation is of utmost importance because the heart works continuously pumping the blood the different organs. For this the heart needs lot of energy. If the muscles of heart are deprived from the enough supply of pure blood, heart attack may result.

Double circulation 

In one complete circulation, blood enters into the heart twice. Blood enters into the heart(left atrium) once in the form of pure blood from the lungs ( pulmonary circulation). The second time, blood enters into the heart(right atrium) in the form of impure blood from the systemic circulation. In this way, the human heart is said to be having double circulation. 

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