WORKING OF HEART:

WORKING OF HEART:

Left side- 

(i)  Left atrium relaxes & the Oxygenated blood enters it from the lungs through the pulmonary vein.

(ii)  Left atrium contracts & the blood enters the left ventricle through the valve.

(iii) Left Ventricle contracts and the blood is pumped into the largest artery ‘Aorta’ and is carried to all parts of the body.

Right side- 

(i) Right atrium relaxes & the deoxygenated blood from the body enters it  through superior and inferior Vena cava.

 (ii)  Right atrium contracts & the blood enters the right Ventricle through the valve.

 (iii) Right Ventricle contracts and the blood is pumped into the Pulmonary artery and is carried to lungs.

Valves - 

It ensure unidirectional flow of blood and prevent the backward flow of blood.

Pulmonary vein is the only vein that carries Oxygenated blood from lungs to heart.

Aorta is the only artery that carries De-oxygenated blood from heart to lungs.

Double circulation in man- because the blood passes through the heart twice in one complete cycle of the circulation.


Capillaries- 

(i) Form the connection between arteries & veins.

(ii) Walls are one cell thick only for easy exchange of blood.

Platelets- Plug the leaks of arteries and veins by clotting the blood. 

Lymph- Extracellular fluid similar to plasma but colourless with lesser protein. 

Function of lymph-

(i) Transportation of digested & absorbed fats from the small intestine.


(ii) Drains excess fluid from the intercellular spaces back in the blood.


Higher animals- E.g., birds, mammals. 

(i) Oxygenated blood & Deoxygenated blood are completely separate for efficient Oxygen supply. 

(ii) This is to fulfil higher energy needs and to maintain body temperature (warm blooded animals). 

Amphibians & reptiles- have 3 chambered heat where little mixing of Oxygenated blood & De-oxygenated blood takes place. Therefore their body temperature varies with the temperature of the environment. (cold blooded animals)