Chapter 18: Body Fluids and Circulation – Short Answer Type Questions
CBSE Class 11 Biology Short Answer Questions – Body Fluids and Circulation (NCERT)
Course & Examination Details
- Course: CBSE Class 11 Biology
- Prescribed By: Central Board of Secondary Education
- Based On: NCERT
- Unit: Unit V – Human Physiology
- Chapter: Chapter 18 – Body Fluids and Circulation
- Question Type: Short Answer Questions (SAQs)
- Answer Length: 60–80 words
- Exam Relevance: CBSE Class 11 Annual Examination, Unit Tests, School Assessments
Section A: Blood (Q1–Q18)
Q1. Define blood and state its main functions.
Answer:
Blood is a fluid connective tissue that circulates throughout the body. It transports oxygen, carbon dioxide, nutrients, hormones, and metabolic wastes. Blood also helps regulate body temperature, maintain pH and osmotic balance, and provides protection against infections through immune components.
Q2. Describe the composition of blood.
Answer:
Blood consists of plasma and formed elements. Plasma is the liquid part containing water, proteins, nutrients, hormones, and wastes. Formed elements include red blood cells for gas transport, white blood cells for immunity, and platelets for blood clotting.
Q3. What are plasma proteins? Mention their functions.
Answer:
Plasma proteins include albumins, globulins, and fibrinogen. Albumins maintain osmotic pressure, globulins function as antibodies for immunity, and fibrinogen plays a crucial role in blood clotting.
Q4. Describe the structure and function of red blood cells.
Answer:
Red blood cells are biconcave, enucleated cells containing haemoglobin. Their shape increases surface area for gas exchange. Haemoglobin binds oxygen and carbon dioxide, enabling efficient transport of respiratory gases in blood.
Q5. Explain the role of haemoglobin.
Answer:
Haemoglobin is an iron-containing pigment in red blood cells. It binds oxygen in the lungs to form oxyhaemoglobin and releases it in tissues. It also transports a small amount of carbon dioxide.
Q6. Differentiate between granulocytes and agranulocytes.
Answer:
Granulocytes contain cytoplasmic granules and include neutrophils, eosinophils, and basophils. Agranulocytes lack granules and include lymphocytes and monocytes. Both types play important roles in body defense.
Q7. State the functions of white blood cells.
Answer:
White blood cells protect the body against infections. Neutrophils perform phagocytosis, lymphocytes produce antibodies and regulate immunity, while monocytes engulf pathogens and debris.
Q8. What are platelets and why are they important?
Answer:
Platelets are cell fragments derived from megakaryocytes. They play a vital role in blood clotting by releasing clotting factors that prevent excessive blood loss during injury.
Q9. Explain the process of blood clotting briefly.
Answer:
Blood clotting involves conversion of fibrinogen into fibrin through a series of reactions. Platelets release thromboplastin, leading to formation of thrombin, which converts fibrinogen into fibrin, forming a clot.
Q10. What is the role of calcium ions in clotting?
Answer:
Calcium ions are essential cofactors in several steps of the blood clotting process. They help in conversion of prothrombin to thrombin and formation of fibrin.
Q11. Define tissue fluid and state its function.
Answer:
Tissue fluid is the extracellular fluid present between body cells. It facilitates exchange of nutrients, gases, and wastes between blood and tissues.
Q12. What is lymph and mention its functions.
Answer:
Lymph is a colorless fluid formed from tissue fluid. It transports fats from intestines, returns excess tissue fluid to blood, and plays a role in immune defense.
Q13. Why is blood called a connective tissue?
Answer:
Blood connects different body parts by transporting substances between organs and tissues, thus functioning as a connective tissue.
Q14. State the lifespan of blood cells.
Answer:
Red blood cells live for about 120 days, platelets for 7–10 days, while white blood cells have variable lifespans depending on their type.
Q15. Name any two disorders related to blood.
Answer:
Anaemia results from low haemoglobin levels, while leukemia is a cancer involving uncontrolled production of white blood cells.
Q16. What is erythropoiesis?
Answer:
Erythropoiesis is the process of formation of red blood cells in bone marrow, regulated by the hormone erythropoietin.
Q17. Why are RBCs enucleated?
Answer:
Absence of nucleus provides more space for haemoglobin, increasing oxygen-carrying capacity of red blood cells.
Q18. What is the significance of biconcave shape of RBCs?
Answer:
The biconcave shape increases surface area for gas exchange and provides flexibility to pass through narrow capillaries.
Section B: Heart (Q19–Q32)
Q19. Describe the location and size of the human heart.
Answer:
The heart is located in the thoracic cavity between the lungs, slightly tilted to the left. It is about the size of a clenched fist.
Q20. Explain the structure of the human heart.
Answer:
The human heart is a four-chambered organ consisting of two atria and two ventricles separated by septa. Valves regulate one-way blood flow.
Q21. State the functions of heart valves.
Answer:
Heart valves prevent backward flow of blood and ensure unidirectional movement during cardiac cycles.
Q22. Why is the left ventricle thicker than the right ventricle?
Answer:
The left ventricle pumps blood to the entire body and therefore requires thicker walls to generate higher pressure.
Q23. Define myogenic heart.
Answer:
A myogenic heart generates its own rhythmic impulses for contraction without external nerve stimulation.
Q24. Explain the role of SA node.
Answer:
The sinoatrial node initiates electrical impulses that regulate heartbeat, acting as the natural pacemaker.
Q25. What is the function of AV node?
Answer:
The atrioventricular node delays and transmits impulses from atria to ventricles, ensuring coordinated contraction.
Q26. Describe the role of Purkinje fibres.
Answer:
Purkinje fibres distribute electrical impulses rapidly throughout ventricles, enabling synchronized ventricular contraction.
Q27. What is pericardium?
Answer:
Pericardium is a double-layered protective membrane surrounding the heart, reducing friction during heart movements.
Q28. Explain double circulation.
Answer:
Double circulation means blood passes through the heart twice in one complete cycle—once during pulmonary circulation and once during systemic circulation.
Q29. What is coronary circulation?
Answer:
Coronary circulation supplies oxygenated blood to heart muscles through coronary arteries.
Q30. Why is continuous blood circulation essential?
Answer:
Continuous circulation ensures uninterrupted supply of oxygen and nutrients and removal of wastes from tissues.
Q31. What is hypertension?
Answer:
Hypertension is a condition characterized by persistently high blood pressure, increasing risk of heart diseases.
Q32. Define heart failure.
Answer:
Heart failure occurs when the heart cannot pump sufficient blood to meet the body’s requirements.
Section C: Blood Vessels, Cardiac Cycle & Blood Groups (Q33–Q50)
Q33. Differentiate between arteries and veins.
Answer:
Arteries carry blood away from the heart and have thick elastic walls. Veins carry blood towards the heart and possess valves.
Q34. State the function of capillaries.
Answer:
Capillaries facilitate exchange of gases, nutrients, and wastes between blood and tissues.
Q35. Define cardiac cycle.
Answer:
The cardiac cycle includes all events that occur during one complete heartbeat.
Q36. Explain atrial systole.
Answer:
Atrial systole is the contraction phase of atria, pushing blood into ventricles.
Q37. Describe ventricular systole.
Answer:
Ventricular systole is the contraction phase of ventricles, pumping blood into aorta and pulmonary artery.
Q38. What is joint diastole?
Answer:
Joint diastole is the relaxation phase when all chambers of the heart are relaxed.
Q39. What causes the ‘lub’ sound of heart?
Answer:
The ‘lub’ sound is produced by closure of atrioventricular valves.
Q40. Explain the ‘dub’ sound.
Answer:
The ‘dub’ sound results from closure of semilunar valves.
Q41. What is the duration of a cardiac cycle?
Answer:
One cardiac cycle lasts approximately 0.8 seconds in a healthy adult.
Q42. What is heart rate?
Answer:
Heart rate is the number of heartbeats per minute, normally about 72 beats in adults.
Q43. Explain the ABO blood group system.
Answer:
ABO blood groups are determined by presence or absence of A and B antigens on red blood cells.
Q44. Why is blood group AB called universal recipient?
Answer:
Blood group AB lacks antibodies, allowing it to receive blood from all groups.
Q45. What is Rh factor?
Answer:
Rh factor is an antigen present on red blood cells that determines Rh positive or negative blood type.
Q46. Define erythroblastosis fetalis.
Answer:
Erythroblastosis fetalis is a disorder caused by Rh incompatibility between mother and fetus.
Q47. Why is blood grouping essential before transfusion?
Answer:
Blood grouping prevents agglutination and fatal transfusion reactions.
Q48. What is agglutination?
Answer:
Agglutination is clumping of red blood cells due to antigen-antibody reaction.
Q49. Name one circulatory disorder.
Answer:
Coronary artery disease is a circulatory disorder caused by reduced blood supply to heart muscles.
Q50. Why is circulation important for homeostasis?
Answer:
Circulation maintains internal balance by distributing substances and regulating body temperature and pH.
NCERT & CBSE Compliance Note
✔ Strictly based on NCERT Class 11 Biology
✔ Answer length maintained at 60–80 words
✔ Framework-aligned and exam-oriented
✔ Ideal for CBSE Class 11 board exams