Blood Vascular System:

Circulatory System of Class 11

Having vessels for carrying blood and a heart for pumping.

Blood circulation in vertebrates : Blood circulation was discovered by William harvey. In case of vertebrates, blood circulation is of closed type, which can be grouped into two categories :

(a) Single circulation

(b) Double circulation

Differences between single and double circulation

Single circulation Double circulation
(1) Blood flows only once through

the heart in a complete cycle

(1) Blood flows in two circuit pulmonary and systemic.
(2) Heart pumps only deoxygenated blood, hence called Venous Heart.

hence called Venous Heart.

(2) Heart pumps both deoxygenated and oxygenated

blood to lungs and body respectively,

hence called arteriovenous heart.

(3) Blood is oxygenated in gills. (3) Blood is oxygenated in lungs.
(4) Less efficient as gill capillaries slow down the blood flow.

So, the body receives blood at a low pressure which decreases the

rate of O2 supply to the cells i.e. keeps the metabolic rate low.

(4) More efficient as blood flows at higher pressure,

especially in birds and mammals, which increases

the rate of food and O2 supply to the cell and also rapid

removal of wastes from them i.e. provides a higher metabolic rate.

(5) Found only in fishes. (5) Found in amphibians, reptiles, birds and mammals.


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