IGCSE Biology: Transport in Animals (Part 1)

Overview

• Focus on the circulatory systems in animals, specifically fish and mammals.
• Importance of circulatory system: transports nutrients and gases.

Single Circulatory System in Fish

• Heart Chambers: Two chambers - an atrium and a ventricle.
• Circulation Path:
  • Blood passes the heart once per circuit.
  • Oxygenation: Occurs at gill capillaries.
  • Blood Flow:
    • Deoxygenated blood from body -> Atrium -> Ventricle -> Gill capillaries (oxygenated) -> Body capillaries.
  • Circulation Types:
    • Gill Circulation: Blood to gills.
    • Systemic Circulation: Blood to body.

Double Circulatory System in Mammals

• Heart Chambers: Four chambers - two atria and two ventricles.
• Circulation Path:
  • Blood passes the heart twice per circuit.
  • Oxygenation:
    • Deoxygenated blood enters right atrium via vena cava, moves to right ventricle, then to lungs (oxygenated).
    • Oxygenated blood returns to left atrium via pulmonary vein, moves to left ventricle, then to the body.
  • Circulation Types:
    • Pulmonary Circulation: Right side pumps to lungs.
    • Systemic Circulation: Left side pumps to body.
• Advantages:
  • Higher blood pressure and efficient oxygen/glucose delivery.

Structures of the Mammalian Heart

• Right Atrium: Receives deoxygenated blood through vena cava.
• Tricuspid Valve: Prevents backflow into atria.
• Right Ventricle & Semilunar Valve: Pumps deoxygenated blood to lungs.
• Left Atrium: Receives oxygenated blood through pulmonary vein.
• Bicuspid Valve: Prevents backflow into atrium.
• Left Ventricle & Semilunar Valve: Pumps oxygenated blood to body.
• Aorta: Distributes oxygenated blood around the body.
• Coronary Arteries: Supply blood to heart tissue.

Muscular Walls

• Ventricles have thicker walls than atria; left ventricle thicker than right.
• Higher pressure needed for systemic circulation.

Monitoring Heart Activity

• Methods: ECG, pulse rate, stethoscope.
• Exercise increases heart rate to meet oxygen/glucose demands.

Coronary Heart Disease (CHD)

• Definition: Blockage in coronary arteries, leading to heart attacks.
• Causes: Cholesterol buildup in arteries.
• Risk Factors:
  • Poor diet, lack of exercise, stress, smoking, genetics, age, and gender.
• Prevention:
  • Quitting smoking, healthy diet, regular exercise.

Conclusion

• End of Part 1 of Chapter 9: Transport in Animals.
• Subscribe for more IGCSE revisions.