Structure & Function of the Heart (Edexcel IGCSE Biology)

• 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
• 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