In the previous section you learnt that blood transports oxygen and carbon dioxide throughout the body.
But how does blood get transported from one part of the body to another?
For the purpose of tranportation we have the human circulatory system - at the center of which is the heart.
The heart pumps blood which allows for effective transportation.
In grade 9 you learnt that human beings have a 4 chambered heart. These chambers are necessary to keep the oxygenated and non-oxygenated blood seperate.
The carbon-dioxide rich blood has to reach the lungs, which then remove the CO2 and oxygenate the blood.
The oxygenated blood then has to be tranported to the rest of the organs in the body to ensure body maintenance.
Let's see how blood flows through the heart step by step.
1. Oxygen rich blood from the lungs enters the left atrium of the heart from the pulmonary viens.
2. The left atrium contracts and the oxygen rich blood flows to the left ventricle.
3. When the left ventricle contracts it pushes out the oxygen rich blood which is transported to the body.
4. De-oxygenated blood enters the right atrium through Vena cava from the upper body and the Vena cava from the lower body.
5. The right atrium contracts and pushes the de-oxygenated blood to the right ventricle.
6. The right ventricle then contracts and pushes the de-xygenated blood to the lungs via the pulmonary arteries to get oxygenated.
The valves that you see between the atrium and the ventricle ensures that blood does not flow in the opposite direction when the chambers of the heart contract and relax.
As the blood being pumped from the heart is pumped at high pressure, the vessels that carry the blood from the heart to our organs have to have thick walls.
These vessels are called arteries.
On reaching an organ, arteries divide into smaller vessels which have extremely thin cells walls. Such vessels are called capillaries.
On the other hand the vessels which bring blood back from the organs and to the heart do not need thick walls.
These vessels are called veins.
Veins have valves which ensure that blood only flows in one direction.
On sustaining injury, our circulatory system can develop a leak. This manifests in the form of bleeding.
A large enough leakage of blood from the system can cause the blood pressure to drop and affect the pumping of the heart.
Platelets are specialised cells which circulate in our blood and help in pulgging these leaks by clotting the blood at points of injury.