ICSE Class 10 Biology: Circulatory System — Important Questions with Answers 2026

Short Answer Questions (2-3 Marks)

• Q: Draw a neat labelled diagram of the human heart.
  Ans: The human heart has 4 chambers: Right atrium (receives deoxygenated blood from body via vena cava), Right ventricle (pumps blood to lungs via pulmonary artery), Left atrium (receives oxygenated blood from lungs via pulmonary veins), Left ventricle (pumps blood to body via aorta — thickest wall). Valves: Tricuspid (between RA and RV), Bicuspid/Mitral (between LA and LV), Semilunar valves (in arteries).
• Q: Describe double circulation in humans.
  Ans: Double circulation means blood passes through the heart twice in one complete circuit. (1) Pulmonary circulation: RV → Pulmonary artery → Lungs (oxygenation) → Pulmonary veins → LA. (2) Systemic circulation: LV → Aorta → Body organs (O₂ delivered, CO₂ collected) → Vena cava → RA. Advantage: Maintains separation of oxygenated and deoxygenated blood, ensuring efficient O₂ delivery.
• Q: Differentiate between arteries, veins, and capillaries.
  Ans: Arteries: Carry oxygenated blood (except pulmonary artery), thick elastic walls, deep-seated, no valves, narrow lumen, blood flows under high pressure. Veins: Carry deoxygenated blood (except pulmonary vein), thin walls, superficial, have valves (prevent backflow), wide lumen, low pressure. Capillaries: Thinnest (one cell thick wall), connect arteries to veins, site of exchange of substances between blood and tissues.

Long Answer / Application Questions (4-6 Marks)

• Q: What are the components of blood? State one function of each.
  Ans: (1) Plasma (55%): Liquid part, transports dissolved substances (nutrients, hormones, waste, antibodies). (2) Red Blood Cells (RBCs): Contain haemoglobin, transport O₂. Biconcave disc shape. (3) White Blood Cells (WBCs): Defence against infection — phagocytosis and antibody production. (4) Platelets (Thrombocytes): Help in blood clotting at wound site, prevent blood loss.
• Q: What is blood group? Explain the ABO system.
  Ans: Blood groups are classified based on presence of antigens on RBCs and antibodies in plasma. ABO System: Group A: Antigen A on RBCs, Antibody b in plasma. Group B: Antigen B on RBCs, Antibody a in plasma. Group AB: Both antigens, no antibodies — universal recipient. Group O: No antigens, both antibodies — universal donor. Rh factor: Rh+ (has Rh antigen), Rh- (lacks it).

Exam Tips for This Chapter

• Revise all definitions and laws from Circulatory System — they are commonly asked as 1-2 mark questions
• Practice diagrams related to Circulatory System — neat labelled diagrams carry 2-3 marks
• For numericals, always show formula → substitution → answer with correct units
• Previous year analysis shows Circulatory System carries 8-12 marks in the board exam