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The Heart 💖
The human heart is a pump that pumps blood around the body at different speeds and pressures according to the body’s needs. It can do this because the wall of the heart is made from cardiac muscle.
How the Heart Pumps? 💞
- Blood enters the atria. It cannot pass into the ventricles because the bicuspid (mitral) and tricuspid valves are closed.
- The walls of the atria contract, raising the pressure of the blood. This forces open the valves and blood passes through into the ventricles.
- When the ventricles are full, the contract, increasing blood pressure in the two chambers and closing the valves.
- The ventricles continue to contract, forcing semi-lunar valves at the base of the aorta and the pulmonary artery to open. The pulmonary artery carries blood to the lungs. The aorta has branches that carry blood to other parts of the body.
- As the ventricles empty, the higher pressure in the aorta and pulmonary artery closes the valves. The cycle then begins again.
Diagram : The structure of heart
Adaptations of the Heart
In I/GCSE Biology, when a chamber of the heart is contracting, it is systole. When it is not, it is diastole. The structure of the heart is adapted to its functions in several ways:
- The septum divides the right and left side of the heart. The right ventricle pumps blood only to the lungs, whereas, the left ventricle pumps blood to other parts of the body. This requires so much pressure, therefore the left ventricle is bigger.
- Valves prevent backflow of blood.
- The walls of the atria are thin. They can be stretched to receive blood and can contract to push blood through the tricuspid and mitral valves.
- Cardiac muscle can contract and relax continuously without becoming fatigued.
- It also has its own blood supply. The coronary artery carries the blood and gives it to the capillaries where it transports the blood to the cardiac muscle. Blood is returned to the right atrium via the coronary veins.
That's the end of the topic!
Drafted by Joey (Biology)