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Structure & Function of the Heart (Edexcel IGCSE Biology)
Revision Note
Structure & Function of the Heart
- The heart organ is a double pump
- Oxygenated blood from the lungs enters the left side of the heart and is pumped to the rest of the body (the systemic circuit)
- The left ventricle has a thicker muscle wall than the right ventricle as it has to pump blood at high pressure around the entire body,
- Deoxygenated blood from the body enters the right side of the heart and is pumped to the lungs (the pulmonary circuit)
- The right ventricle is pumping blood at lower pressure to the lungs
- A muscle wall called the septum separates the two sides of the heart
- Oxygenated blood from the lungs enters the left side of the heart and is pumped to the rest of the body (the systemic circuit)
- Blood is pumped towards the heart in veins and away from the heart in arteries
- The coronary arteries supply the cardiac muscle tissue of the heart with oxygenated blood
- As the heart is a muscle it needs a constant supply of oxygen (and glucose) for aerobic respiration to release energy to allow continued muscle contraction
- Valves are present to prevent blood flowing backwards
Structure of the Heart
The pathway of blood through the heart
- Deoxygenated blood coming from the body flows through the vena cava and into the right atrium
- The atrium contracts and the blood is forced through the tricuspid (atrioventricular) valve into the right ventricle
- The ventricle contracts and the blood is pushed through the semilunar valve into the pulmonary artery
- The blood travels to the lungs and moves through the capillaries past the alveoli where gas exchange takes place
- Low pressure blood flow on this side of the heart prevents damage to the capillaries in the lungs
- Oxygenated blood returns via the pulmonary vein to the left atrium
- The atrium contracts and forces the blood through the bicuspid (atrioventricular) valve into the left ventricle
- The ventricle contracts and the blood is forced through the semilunar valve and out through the aorta
- Thicker muscle walls of the left ventricle produce a high enough pressure for the blood to travel around the whole body
Examiner Tip
Remember : Arteries carry blood Away from the heart.
When explaining the route through the heart we usually describe it as one continuous pathway with only one atrium or ventricle being discussed at a time, but remember that in reality, both atria contract at the same time and both ventricles contract at the same time.
Also, the heart is labelled as if it was in the chest so the left side of a diagram is actually the right hand side and vice versa
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