Transportation in Human Beings:
Most of the nutrients, waste products, useful gases, etc are carried by our blood. Thus, this blood needs to be pushed to each and every corner of the body, that too continuously! This job of pumping the blood around the body is done by our heart!
The heart is a muscular organ which is as big as our fist.
Now, since 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.
Now let us see how this happens!
On your screen you now see sectional view of the human heart, which you should definitely practice drawing as it has been asked in previous years.

- The oxygen-rich blood from the lungs comes to the upper-left chamber of the heart, the left atrium. The left atrium relaxes when it is collecting this blood and 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 – right chamber, 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.
Note that not all organisms have 4-chambered heart. Amphibians or many reptiles have three-chambered hearts, while fishes, on the other hand, have only two chambered hearts.
This pumping of heart around the body takes place through blood vessels called veins and arteries. On your board now you can see differences in these two, and you should remember them.
Arteries |
Veins |
Vessels which carry blood away from the heart to various organs of the body |
collect the blood from different organs and bring it back to the heart |
These have thick, elastic walls as blood emerges from heart under high pressure. |
They have valves that ensure blood flows in only one direction |
These are usually positioned deeper within the body |
These are present closer beneath the surface of the skin |
Two major components of blood are platelets and lymph. You can read more about these on your screen now.
- Platelets – when we are injured, blood starts flowing out of the body. This can cause a decrease in blood pressure, decreasing efficiency of pumping system. Platelet cells circulate around the body and plug such leaks by helping to clot the blood at these points of injury.
- Lymph – When some amount of plasma, proteins and blood cells leak through the capillaries, they form lymph. It is colourless and contains less protein. It carries digested and absorbed fat from intestine and drains excess fluid from extra-cellular space back into the blood.
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