Body Fluids and Circulation (NCERT Practice Paper)

Q1. Match the blood groups with their antigens and antibodies:

Group	Antigen on RBC	Antibody in Plasma
A. Group A	(I) nil	(II) anti-A, B
B. Group AB	(III) A, B	(IV) nil
C. Group O	(V) A	(VI) anti-B

Correct Answer: (a)
Group A has antigen A and anti-B antibodies (V–VI). Group AB has both A and B antigens and no antibodies (III–IV). Group O has no antigens and both anti-A and anti-B antibodies (I–II). The correct pairing is A: V–VI, B: III–IV, C: I–II.

Q2. Match the plasma proteins with their primary functions:

Column-I	Column-II
A. Fibrinogen	(I) Osmotic balance
B. Globulins	(II) Clotting / Coagulation
C. Albumins	(III) Defense mechanism

Correct Answer: (a)
Fibrinogen is essential for clotting (coagulation). Globulins function as antibodies in immune defense. Albumins maintain osmotic pressure. This pairing is standard: A–II, B–III, C–I. The other options incorrectly swap these functions.

Q3. Which ion plays a very important role in blood clotting?

Correct Answer: (c)
Calcium ions (Ca²⁺) are essential for several steps in the coagulation cascade, including the conversion of prothrombin to thrombin. They act as a cofactor for clotting factors. Without adequate calcium, blood clotting is impaired. Other ions like sodium, potassium, and magnesium are not directly involved in the clotting mechanism.

Q4. Sympathetic nerves (ANS) can ______ the rate of heart beat.

Correct Answer: (b)
Stimulation of sympathetic nerves releases noradrenaline, which increases heart rate (positive chronotropic effect) and force of contraction. This prepares the body for 'fight or flight' responses. Parasympathetic stimulation has the opposite effect, decreasing heart rate. Sympathetic stimulation does not stop the heart.

Q5. Heart failure is not the same as cardiac arrest. Cardiac arrest occurs when:

Correct Answer: (a)
Cardiac arrest is a sudden cessation of heart activity, meaning the heart stops pumping blood. This is a medical emergency requiring CPR and defibrillation. Heart failure is a chronic condition where the heart cannot pump enough blood to meet body needs, often causing fluid congestion, but the heart may still be beating.

Q6. Platelets, also called thrombocytes, are cell fragments produced from:

Correct Answer: (b)
Platelets are not true cells but fragments of large bone marrow cells called megakaryocytes. They are crucial for blood clotting and vessel repair. They are produced in the red bone marrow and have a short lifespan of about 7–10 days. Spleen, lymphocytes, and basophils are not their source.

Q7. Assertion: Parasympathetic neural signals increase cardiac output. Reason: They increase the rate of heart beat and strength of contraction.

Correct Answer: (d)
Parasympathetic stimulation actually decreases heart rate and the force of contraction, thus reducing cardiac output. The assertion is false, and the reason is also false because parasympathetic signals do not increase rate or strength. The correct statement would be that sympathetic signals increase cardiac output.

Q8. Which of the following describes the 'Z-scheme' or circulation correctly?
(i) Single circulation is found in fishes.
(ii) Incomplete double circulation in amphibians.
(iii) Double circulation in mammals.
(iv) Systemic circulation carries deoxygenated blood to the lungs.

Correct Answer: (a)
Fishes have single circulation. Amphibians have incomplete double circulation. Mammals have complete double circulation. Systemic circulation carries oxygenated blood to the body, not deoxygenated to lungs. So (i),(ii),(iii) correct; (iv) false.

Q9. Match the heart sound with its cause:

Sound	Event
A. First (Lub)	(I) Closure of Semilunar valves
B. Second (Dub)	(II) Closure of Tricuspid/Bicuspid valves

Correct Answer: (a)
The first heart sound (lub) is caused by closure of AV valves (tricuspid and bicuspid). The second sound (dub) is due to closure of semilunar valves. Correct: A–II, B–I.

Q10. Match the ECG waves with their events:

Wave	Event
A. P-wave	(I) Repolarisation of ventricles
B. QRS complex	(II) Depolarisation of atria
C. T-wave	(III) Depolarisation of ventricles

Correct Answer: (a)
P-wave = atrial depolarisation. QRS complex = ventricular depolarisation. T-wave = ventricular repolarisation. Thus A–II, B–III, C–I is correct. The other options mix up the events.

Q11. Which statements about CAD are correct?
(i) Also called atherosclerosis.
(ii) Affects vessels supplying heart muscle.
(iii) Caused by deposits of calcium, fat, and cholesterol.
(iv) Makes the lumen of arteries wider.

Correct Answer: (a)
Coronary artery disease (CAD) is atherosclerosis of coronary arteries. It is caused by plaque deposits (calcium, fat, cholesterol) that narrow the lumen, not widen. So (i),(ii),(iii) correct; (iv) false.

Q12. Fishes have a ______ chambered heart.

Correct Answer: (a)
Fishes possess a two-chambered heart consisting of one atrium and one ventricle. This simple heart pumps deoxygenated blood to the gills for oxygenation and then to the rest of the body. The single circulation path is efficient for aquatic life. Three-chambered hearts are found in amphibians and most reptiles, and four-chambered in birds and mammals.

Q13. What is the average number of RBCs in a healthy adult man per mm³ of blood?

Correct Answer: (a)
A healthy adult male has about 5 to 5.5 million red blood cells per cubic millimetre of blood. This range is typical and ensures adequate oxygen transport. The other options refer to WBC count, platelet count, or haemoglobin concentration, not RBC count.

Q14. Which WBCs are phagocytic cells that destroy foreign organisms?

Correct Answer: (b)
Neutrophils and monocytes are the main phagocytic cells that engulf and digest pathogens and debris. Neutrophils are quick responders, while monocytes mature into macrophages that clean up larger particles. Lymphocytes are involved in immune responses but are not primarily phagocytic, and platelets help in clotting.

Q15. Which reptile has a 4-chambered heart unlike others?

Correct Answer: (c)
Among reptiles, crocodiles are unique in having a four-chambered heart, which completely separates oxygenated and deoxygenated blood. Other reptiles (snakes, lizards, turtles) have a three-chambered heart with partial mixing. This adaptation in crocodiles supports their more active lifestyle and efficient oxygen delivery.

Q16. Which condition is characterized by acute chest pain when not enough oxygen reaches the heart muscle?

Correct Answer: (c)
Angina pectoris is the medical term for chest pain caused by reduced oxygen supply to the heart muscle, usually due to narrowed coronary arteries. The pain is often triggered by exertion or stress and is a warning sign of underlying heart disease. Heart failure and hypertension are different conditions.

Q17. Assertion: Closed circulatory system is considered more advantageous than open system. Reason: The flow of fluid can be more precisely regulated in a closed system.

Correct Answer: (a)
In a closed circulatory system, blood flows within vessels, allowing precise control of distribution and pressure to different organs. This enables rapid and efficient delivery of oxygen and nutrients, especially in active animals. The reason correctly explains the advantage over the open system.

Q18. Which are the most abundant cells among total WBCs?

Correct Answer: (d)
Neutrophils are the most numerous white blood cells, accounting for 60–65% of total leucocytes. They are the first responders to bacterial infections and are highly phagocytic. Basophils are the least abundant, and eosinophils and monocytes are intermediate in percentage.

Q19. Select the correct statements for Rh grouping:
(i) Observed in nearly 80 per cent of humans.
(ii) Rh antigen is similar to one in Rhesus monkeys.
(iii) Rh incompatibility can lead to erythroblastosis foetalis.
(iv) Rh negative individuals have Rh antibodies naturally in plasma.

Correct Answer: (a)
About 80% of humans are Rh positive. Rh antigen is named after Rhesus monkeys. Rh incompatibility can cause erythroblastosis foetalis. However, Rh-negative individuals do not have natural antibodies; they develop them only after exposure. Thus (i),(ii),(iii) correct; (iv) false.

Q20. Assertion: Tricuspid valve guards the right AV opening. Reason: It is formed of three muscular flaps.

Correct Answer: (a)
The tricuspid valve consists of three cusps (flaps) and is located between the right atrium and right ventricle. Its name derives from its three flaps, which prevent backflow during ventricular contraction. The reason correctly describes the anatomical feature that gives the valve its name and location.

Q21. Match the blood vessel layers:

Layer	Components
A. Tunica intima	(I) Smooth muscle and elastic fibres
B. Tunica media	(II) Squamous endothelium
C. Tunica externa	(III) Fibrous connective tissue / Collagen

Correct Answer: (a)
Tunica intima is the inner squamous endothelium. Tunica media consists of smooth muscle and elastic fibres. Tunica externa is fibrous connective tissue. Correct: A–II, B–I, C–III.

Q22. Assertion: Erythroblastosis foetalis can be avoided in Rh-ve mothers. Reason: By administering anti-Rh antibodies to the mother immediately after the delivery of the first child.

Correct Answer: (a)
Administration of anti-Rh antibodies (Rh immunoglobulin) to an Rh-negative mother after the birth of an Rh-positive baby prevents her immune system from becoming sensitised. This stops the production of anti-Rh antibodies that would harm subsequent Rh-positive fetuses. Both statements are true and the reason correctly explains the preventive measure.

Q23. Match the portal systems:

System	Pathway
A. Hepatic portal	(I) Heart to cardiac musculature
B. Renal portal	(II) Intestine to Liver
C. Coronary system	(III) Kidney to lower body (standard bio context)

Correct Answer: (a)
Hepatic portal: intestine to liver. Renal portal: kidney to lower body (in some vertebrates). Coronary: heart to cardiac muscle. Correct: A–II, B–III, C–I.

Q24. Regarding blood pressure:
(i) Normal BP is 120/80 mm Hg.
(ii) 120 is systolic (pumping) pressure.
(iii) 80 is diastolic (resting) pressure.
(iv) 140/90 indicates hypertension.

Correct Answer: (a)
Normal blood pressure is 120/80 mm Hg, with 120 as systolic and 80 as diastolic. A reading of 140/90 or above is classified as hypertension. All statements are correct.

Q25. Match the leucocyte types with their percentage/description:

Column-I	Column-II
A. Neutrophils	(I) Least abundant (0.5-1%)
B. Basophils	(II) Most abundant (60-65%)
C. Monocytes	(III) Resist infections (2-3%)
D. Eosinophils	(IV) Phagocytic (6-8%)

Correct Answer: (a)
Neutrophils are the most abundant (60–65%). Basophils are the least (0.5–1%). Monocytes are phagocytic and make up 6–8%. Eosinophils resist infections and are 2–3%. The correct matching is A–II, B–I, C–IV, D–III.

Q26. Which of the following plasma proteins is primarily involved in defense mechanisms?

Correct Answer: (c)
Globulins are the plasma proteins that function as antibodies (immunoglobulins) and play a key role in immune defense. Fibrinogen is involved in blood clotting, albumin maintains osmotic pressure, and magnesium is a mineral ion, not a protein. Thus, globulins are the correct choice.

Q27. Regarding electrical leads in a standard ECG:
(i) One to each wrist.
(ii) One to the left ankle.
(iii) Chest leads are used for detailed evaluation.

Correct Answer: (a)
Standard ECG uses limb leads (one on each wrist and one on the left ankle) and chest leads for detailed views. All statements are correct.

Q28. Assertion: A person with blood group O is called a universal donor. Reason: Their RBCs lack both A and B antigens.

Correct Answer: (a)
Group O individuals have no A or B antigens on their red blood cells, so their blood can be transfused to any ABO group without causing agglutination. The reason explains why they are universal donors: the absence of antigens prevents immune rejection. Both statements are true and the reason is the correct explanation.

Q29. Match the circulation pathways:

Type	Example
A. Open	(I) Arthropods
B. Closed	(II) Chordates
C. Double	(III) Mammals

Correct Answer: (a)
Open circulatory system is found in arthropods. Closed is seen in chordates. Double circulation is characteristic of mammals (and birds). Correct: A–I, B–II, C–III.

Q30. Assertion: Albumins are important plasma proteins. Reason: They help in maintaining osmotic balance.

Correct Answer: (a)
Albumins are the most abundant plasma proteins and play a crucial role in maintaining colloid osmotic pressure (oncotic pressure). This osmotic pressure prevents excessive fluid leakage from capillaries into tissues. The assertion and reason are both true, and the reason directly explains the importance of albumins.

Q31. Match heart types with vertebrate groups:

Heart Type	Group
A. 2-chambered	(I) Amphibians and Reptiles
B. 3-chambered	(II) Fishes
C. 4-chambered	(III) Crocodiles, Birds, Mammals

Correct Answer: (a)
Fishes have 2-chambered hearts. Amphibians and most reptiles have 3-chambered hearts. Crocodiles, birds, and mammals have 4-chambered hearts. Correct: A–II, B–I, C–III.

Q32. The sino-atrial node (SAN) is located in which part of the heart?

Correct Answer: (b)
The sino-atrial node (SAN) is situated in the upper right corner of the right atrium, near the opening of the superior vena cava. It is the natural pacemaker that initiates each heartbeat. The atrioventricular node (AVN) is located in the lower left corner of the right atrium, and the inter-ventricular septum contains the bundle of His.

Q33. The volume of blood pumped out by each ventricle during a cardiac cycle is about 70 mL, called:

Correct Answer: (b)
Stroke volume is the amount of blood ejected by each ventricle per contraction, approximately 70 mL in a healthy adult at rest. Cardiac output is the total volume pumped per minute (stroke volume × heart rate, about 5 L/min). Tidal and residual volumes relate to lung capacity, not heart.

Q34. The network of threads formed during blood coagulation is called:

Correct Answer: (b)
During clotting, soluble fibrinogen is converted into insoluble fibrin threads by the enzyme thrombin. These threads form a mesh that traps blood cells and platelets, creating a stable clot. Prothrombin is the precursor to thrombin, and thrombokinase is an enzyme that initiates the cascade.

Q35. Assertion: SAN is called the pacemaker. Reason: It generates the maximum number of action potentials (70-75/min) and initiates heart contraction.

Correct Answer: (a)
The sino-atrial node (SAN) fires at the highest frequency (about 70–75 action potentials per minute) and sets the baseline heart rate. This rhythmic activity spreads to the rest of the heart, establishing it as the pacemaker. Both statements are true, and the reason directly supports the assertion.

Q36. Assertion: Spleen is called the graveyard of RBCs. Reason: RBCs are destroyed in the spleen after their life span of 120 days.

Correct Answer: (a)
The spleen is a primary site for the breakdown of old and damaged RBCs after their 120-day lifespan. This destruction process is why it is metaphorically called the 'graveyard of RBCs'. The reason provides the exact cause, making it a correct explanation.

Q37. Assertion: Atrial systole increases flow of blood into ventricles by about 30%. Reason: SAN generates action potential stimulating atrial contraction.

Correct Answer: (b)
Atrial contraction (systole) adds about 30% more blood to the ventricles before they contract. The SAN initiates this contraction, but the 30% increase is a consequence of the contraction, not the generation of the action potential itself. Thus both are true, but the reason does not fully explain the percentage.

Q38. Which are correct for 'clotting factors'?
(i) Fibrinogen is a plasma protein.
(ii) Fibrins are active threads.
(iii) Factors are present in plasma in an inactive form.

Correct Answer: (a)
Fibrinogen is a plasma protein. Fibrin forms active threads. Clotting factors are mostly present in inactive forms (zymogens) until activated. All statements are correct.

Q39. Regarding the ABO blood grouping system:
(i) Based on surface antigens A and B on RBCs.
(ii) Plasma contains natural antibodies anti-A and anti-B.
(iii) Group AB is the universal recipient.
(iv) Group O is the universal donor.

Correct Answer: (a)
ABO grouping depends on A and B antigens on RBCs, and plasma has corresponding antibodies. Group AB has no antibodies, making it a universal recipient. Group O lacks antigens, making it a universal donor. All statements are correct.

Q40. Assertion: Heart is myogenic in nature. Reason: The normal activities of the heart are regulated by nodal tissue (specialised muscles).

Correct Answer: (a)
A myogenic heart initiates its own contraction rhythm without external nerve impulses. This is due to the nodal tissue (especially the SAN) which has inherent automaticity. The reason correctly explains why the heart is myogenic: its activity is regulated by specialised muscle cells within the heart itself.

Q41. The vascular connection between the digestive tract and liver is the:

Correct Answer: (b)
The hepatic portal system is a special venous pathway that carries blood from the gastrointestinal tract and spleen to the liver. This allows the liver to process nutrients and detoxify substances before they enter systemic circulation. The renal portal system (found in some vertebrates) connects kidneys, and the coronary system serves the heart.

Q42. Assertion: Fishes have single circulation. Reason: Oxygenated blood from gills is supplied to body and deoxygenated returns to heart.

Correct Answer: (a)
In fish, blood passes through the heart only once per complete circuit (from heart to gills, then to body, and back to heart). This single pathway is called single circulation. The reason accurately describes this route and explains why it is a single circulation.

Q43. Select correct statements for 'Regulation of Cardiac Activity':
(i) Heart is myogenic.
(ii) Sympathetic nerves increase heart rate.
(iii) Parasympathetic nerves decrease heart rate.
(iv) Adrenal medullary hormones decrease cardiac output.

Correct Answer: (a)
The heart is myogenic; sympathetic stimulation increases heart rate; parasympathetic decreases it. Adrenal medullary hormones (adrenaline) increase cardiac output, not decrease. So (i),(ii),(iii) correct; (iv) false.

Q44. Regarding Blood Coagulation:
(i) It is a cascade process.
(ii) Thrombin converts fibrinogen into fibrins.
(iii) Prothrombin is converted to thrombin by thrombokinase.
(iv) Platelets are not involved in this process.

Correct Answer: (a)
Clotting is a cascade of enzymatic reactions. Thrombin converts fibrinogen to fibrin. Prothrombin to thrombin conversion requires thrombokinase. Platelets are essential as they release clotting factors, so (iv) is false. Correct: (i),(ii),(iii).

Q45. The opening between the right atrium and the right ventricle is guarded by which valve?

Correct Answer: (c)
The right atrioventricular (AV) opening is guarded by the tricuspid valve, which has three cusps. It prevents backflow of blood from the right ventricle into the right atrium during ventricular contraction. The bicuspid (mitral) valve guards the left AV opening, and semilunar valves are at the bases of the aorta and pulmonary artery.

Q46. The average count of leucocytes (WBCs) per mm³ of blood is:

Correct Answer: (c)
White blood cells typically number 6000 to 8000 per cubic millimetre of blood. This range is much lower than RBCs (millions) and higher than platelets (lakhs). The count can vary with infections or immune responses, but the normal average is in this range.

Q47. Plasma without the clotting factors is called:

Correct Answer: (b)
When clotting factors like fibrinogen are removed from plasma, the remaining fluid is called serum. Serum still contains other proteins, electrolytes, and hormones but cannot clot. Lymph is interstitial fluid, and tissue fluid is similar to plasma but with fewer proteins. Hence, serum is the correct term.

Q48. The duration of a single cardiac cycle in a healthy human is:

Correct Answer: (c)
A cardiac cycle lasts about 0.8 seconds at a normal heart rate of 72 beats per minute. This includes atrial systole, ventricular systole, and joint diastole. At higher heart rates, the cycle shortens, but 0.8 seconds is the standard resting value. 72 seconds would be far too long.

Q49. Which organ is known as the 'graveyard of RBCs'?

Correct Answer: (c)
The spleen is called the graveyard of RBCs because old and worn-out red blood cells are destroyed there by phagocytes. The liver also participates in breaking down haemoglobin, but the spleen is specifically associated with this nickname. The kidney and thymus have different functions, so spleen is the answer.

Q50. RBCs are formed in the ______ in adults.

Correct Answer: (c)
In adults, red blood cells are produced in the red bone marrow of long bones and flat bones. The spleen is the site of RBC destruction, not production. Yellow bone marrow is mostly fat, and the liver produces RBCs only during embryonic development. Thus, red bone marrow is correct.

Q51. The first heart sound (lub) is associated with the closure of:

Correct Answer: (b)
The first heart sound, 'lub', occurs when the atrioventricular (tricuspid and bicuspid) valves close at the start of ventricular systole. This prevents backflow into the atria. The second sound, 'dub', is caused by closure of semilunar valves at the beginning of ventricular diastole.

Q52. Match the disorders with their symptoms:

Disorder	Symptom/Cause
A. Hypertension	(I) Acute chest pain
B. CAD	(II) 140/90 BP
C. Angina	(III) Congestion of lungs
D. Heart failure	(IV) Atherosclerosis

Correct Answer: (a)
Hypertension is defined by 140/90 mm Hg. CAD is atherosclerosis. Angina is acute chest pain. Heart failure often presents with lung congestion. Correct: A–II, B–IV, C–I, D–III.

Q53. Open circulatory system is present in:

Correct Answer: (c)
Arthropods (insects, crustaceans) and most molluscs have an open circulatory system where blood (haemolymph) flows freely through body cavities (sinuses) and bathes organs directly. Annelids and chordates have closed circulatory systems with blood confined to vessels. Mammals are chordates and have a closed system.

Q54. Plasma is a straw coloured, viscous fluid constituting nearly ______ per cent of the blood.

Correct Answer: (c)
Plasma makes up about 55% of the total blood volume. The remaining 45% is the formed elements (RBCs, WBCs, platelets). This proportion is important for maintaining proper viscosity and osmotic balance. The 55% value is a standard average for healthy individuals.

Q55. Assertion: Hypertension can lead to heart diseases. Reason: High blood pressure affects vital organs like brain and kidney.

Correct Answer: (a)
Chronic hypertension damages blood vessels and strains the heart, increasing the risk of heart attack, stroke, and kidney failure. The reason explains how high blood pressure affects multiple organs, which is why it contributes to heart diseases. Both statements are true and causally linked.

Q56. The QRS complex in a standard ECG represents:

Correct Answer: (b)
The QRS complex marks the rapid depolarisation of the ventricles, which initiates ventricular systole. This is the largest wave because the ventricular muscle mass is greater. Atrial depolarisation is represented by the P-wave, and ventricular repolarisation by the T-wave.

Q57. The fluid present in the lymphatic system is called:

Correct Answer: (c)
The lymphatic system carries a fluid called lymph, which is derived from tissue fluid (interstitial fluid) that enters lymphatic capillaries. Lymph is similar to plasma but contains fewer proteins and more lymphocytes. It plays a role in immune function and transport of fats. Plasma and serum are blood components, not lymphatic fluid.

Q58. Which node is called the 'pacemaker' of the heart?

Correct Answer: (c)
The sino-atrial node (SAN) is called the pacemaker because it generates the highest frequency of action potentials (70–75 per minute) and sets the rhythm for the entire heart. The AVN and AV bundle conduct signals but do not initiate rhythm, and Purkinje fibres distribute impulses to the ventricles.

Q59. Regarding the Cardiac Cycle:
(i) Sequential event cyclically repeated.
(ii) Total duration is 0.8 seconds.
(iii) Atrial systole increases blood flow into ventricles by 30%.
(iv) Ventricular systole causes closure of semilunar valves.

Correct Answer: (a)
The cardiac cycle is sequential and lasts 0.8 s. Atrial systole adds about 30% more blood. Ventricular systole causes closure of AV valves, not semilunar; semilunar valves close at the start of diastole. Thus (i),(ii),(iii) correct; (iv) false.

Q60. Which of the following is a special connective tissue consisting of a fluid matrix, plasma, and formed elements?

Correct Answer: (b)
Blood is a fluid connective tissue that has a liquid matrix (plasma) and cellular components (formed elements). It connects various parts of the body by transporting gases, nutrients, and wastes. Unlike lymph, it contains red blood cells and platelets. Serum is plasma without clotting factors, and water is not a tissue.

Q61. Regarding Heart failure:
(i) Heart failure is the same as cardiac arrest.
(ii) It is often called congestive heart failure.
(iii) Congestion of lungs is a symptom.

Correct Answer: (a)
Heart failure is not the same as cardiac arrest; it is a chronic condition where the heart cannot pump adequately. It is often called congestive heart failure, and lung congestion is a common symptom. So (ii) and (iii) are correct; (i) false.

Q62. Which cells secrete histamine, serotonin, and heparin?

Correct Answer: (a)
Basophils are granular leukocytes that release histamine, serotonin, and heparin during allergic and inflammatory reactions. These substances dilate blood vessels, increase permeability, and prevent clotting. Eosinophils combat parasites, monocytes are phagocytic, and neutrophils are also phagocytic but do not secrete these mediators.

Q63. Which of the following statements about WBCs are true?
(i) They are colourless due to lack of haemoglobin.
(ii) They are nucleated.
(iii) Neutrophils are the least abundant.
(iv) Monocytes are phagocytic.

Correct Answer: (a)
WBCs lack haemoglobin, are nucleated, and monocytes are phagocytic. However, neutrophils are the most abundant, not least; basophils are least abundant. So (i), (ii), (iv) are true; (iii) is false.

Q64. Choose the correct statements regarding ECG interpretation:
(i) P-wave marks atrial depolarisation.
(ii) QRS complex marks ventricular depolarisation.
(iii) T-wave marks ventricular repolarisation.
(iv) Any deviation from standard shape indicates potential disease.

Correct Answer: (a)
P-wave = atrial depolarisation, QRS = ventricular depolarisation, T-wave = ventricular repolarisation. Deviations from the normal ECG pattern can signal cardiac abnormalities. All statements are correct.

Q65. Regarding the lymphatic system:
(i) Lymph is colourless.
(ii) Contains specialised lymphocytes.
(iii) Drains back to major veins.
(iv) Transports oxygen to tissues.

Correct Answer: (a)
Lymph is colourless, contains lymphocytes, and returns to the bloodstream via major veins. It does not transport oxygen; that is the role of RBCs. Thus (i),(ii),(iii) correct; (iv) false.

Q66. What is the average life span of RBCs?

Correct Answer: (b)
Red blood cells have an average lifespan of about 120 days. After this period, they are removed by macrophages in the spleen and liver. This timeframe allows for continuous replacement and maintains a stable RBC count. Other durations are incorrect for mammalian RBCs.

Q67. Assertion: Lymph is a colourless fluid. Reason: It lacks RBCs and certain large proteins.

Correct Answer: (a)
Lymph is indeed colourless because it lacks red blood cells (which give blood its red colour) and has fewer large proteins than plasma. This composition results from filtration of blood plasma through capillary walls. The reason explains why lymph appears colourless.

Q68. Correct statements about the Pace-maker system:
(i) SAN is the pacemaker.
(ii) It is auto-excitable.
(iii) AVN is located in the left atrium.
(iv) Bundle of His transmits signals through ventricular musculature.

Correct Answer: (a)
SAN is the pacemaker and is auto-excitable. AVN is in the lower left corner of the right atrium, not left atrium. The Bundle of His transmits signals to ventricles. So (i),(ii),(iv) correct; (iii) false.

Q69. Assertion: Fibrins trap damaged formed elements of blood. Reason: Fibrins are formed from inactive fibrinogens by thrombin.

Correct Answer: (b)
Fibrin threads entangle platelets and blood cells to form a clot. The conversion of fibrinogen to fibrin by thrombin is a key step in clotting. While both statements are true, the reason describes the formation of fibrins, not directly why they trap formed elements; trapping is a physical property of the fibrin network.

Q70. Heart is called myogenic because normal activities are regulated by:

Correct Answer: (c)
A myogenic heart generates its own rhythmic contractions without external neural input. In humans, the sino-atrial node (nodal tissue) acts as the pacemaker, initiating each heartbeat. Although the nervous and hormonal systems can modulate the rate, the basic rhythm originates within the heart muscle itself.

Q71. Assertion: Human beings have double circulation. Reason: Two separate circulatory pathways (pulmonary and systemic) are present.

Correct Answer: (a)
Human double circulation involves two circuits: pulmonary (to lungs) and systemic (to body). Blood passes through the heart twice per complete cycle. The presence of these two pathways is the definition of double circulation, so the reason accurately explains the assertion.

Q72. Each artery and vein consists of three layers. The inner lining of squamous endothelium is called:

Correct Answer: (c)
The innermost layer of blood vessels is the tunica intima, composed of a thin squamous endothelium that provides a smooth surface for blood flow. The tunica media is the middle layer of smooth muscle and elastic fibres, and the tunica externa is the outer connective tissue layer. Pericardium is the sac surrounding the heart.

Q73. Match the formed elements with their counts per mm³ of blood:

Column-I	Column-II
A. Erythrocytes	(I) 6000 – 8000
B. Leucocytes	(II) 5 million – 5.5 million
C. Platelets	(III) 1,50,000 – 3,50,000

Correct Answer: (a)
Erythrocytes (RBCs) number about 5–5.5 million/mm³. Leucocytes (WBCs) are 6000–8000/mm³. Platelets range from 1.5–3.5 lakh/mm³ (150,000–350,000). The correct matching is A–II, B–I, C–III. This is the typical count range for each.

Q74. Identify the correct features of the human heart:
(i) Situated in the thoracic cavity, slightly tilted to the left.
(ii) Protected by a double walled bag called pericardium.
(iii) Has four chambers (two atria, two ventricles).
(iv) Walls of atria are thicker than ventricles.

Correct Answer: (a)
The heart lies in the thoracic cavity, tilted left, is enclosed in pericardium, and has four chambers. However, ventricular walls are thicker than atrial walls because they pump blood farther. So (i),(ii),(iii) are true; (iv) false.

Q75. The second heart sound (dub) is associated with the closure of:

Correct Answer: (b)
The second heart sound, 'dub', occurs when the semilunar valves (aortic and pulmonary) close at the beginning of ventricular diastole. This prevents blood from flowing back into the ventricles from the aorta and pulmonary artery. The first sound is caused by closure of AV valves.

Q76. A blood pressure reading of 140/90 or higher is considered:

Correct Answer: (b)
A reading of 140/90 mm Hg or above is classified as hypertension (high blood pressure). Normal blood pressure is around 120/80 mm Hg. Hypotension is a lower-than-normal reading, and athletic individuals may have lower resting pressures, but 140/90 is consistently recognised as hypertensive.

Q77. Assertion: The T-wave in an ECG represents the return of ventricles to normal state. Reason: This marks the end of systole.

Correct Answer: (a)
The T-wave reflects ventricular repolarisation, which is the electrical recovery of ventricles after contraction. This repolarisation signals the end of systole and the beginning of diastole. Both statements are true, and the reason correctly interprets the significance of the T-wave.

Q78. Identify correct descriptions for Angina:
(i) Also called 'angina pectoris'.
(ii) Symptom of acute chest pain.
(iii) Occurs when not enough oxygen reaches heart muscle.
(iv) Only occurs in elderly people.

Correct Answer: (a)
Angina pectoris is chest pain due to insufficient oxygen supply to heart muscle. It can occur in any age group, not only the elderly. So (i),(ii),(iii) correct; (iv) false.

Q79. Which of the following are correctly described by the given statements?
(i) Constitutes nearly 55 per cent of the blood.
(ii) 90-92 per cent is water.
(iii) Contains proteins like Fibrinogen, Globulins and Albumins.

Correct Answer: (b)
Plasma makes up 55% of blood, is about 90–92% water, and contains fibrinogen, globulins, and albumins. Formed elements are the cells, lymph is interstitial fluid, and serum lacks clotting factors. Therefore, the description fits plasma.

Q80. Assertion: RBCs are biconcave in shape and lack a nucleus in most mammals. Reason: This increases the surface area for the transport of respiratory gases.

Correct Answer: (a)
RBCs are indeed biconcave and enucleated (in mammals). The biconcave shape maximises the surface area-to-volume ratio, facilitating efficient diffusion of oxygen and carbon dioxide. The absence of a nucleus also leaves more space for haemoglobin. Both statements are accurate, and the reason correctly explains the adaptive advantage.

Q81. The human heart is ______ in size.

Correct Answer: (b)
The human heart is roughly the size of a clenched fist, weighing about 250–300 grams. It is located in the thoracic cavity, tilted slightly to the left. This size allows it to pump about 5 litres of blood per minute at rest. Comparisons to an apple, football, or grape are inaccurate.

Q82. Which statements about Lymph are correct?
(i) It is tissue fluid released from capillaries.
(ii) It has the same mineral distribution as plasma.
(iii) It contains specialised lymphocytes.
(iv) Fats are absorbed through it in lacteals.

Correct Answer: (a)
Lymph is formed from tissue fluid, has a similar ionic composition to plasma, contains lymphocytes, and absorbs fats via lacteals. All statements are correct, making 'All are correct' the right option.

Q83. Match the clotting factors with their sequence:

Factor	Action
A. Prothrombin	(I) Forms clot threads
B. Thrombin	(II) Enzyme required to convert fibrinogen
C. Fibrin	(III) Inactive plasma substance

Correct Answer: (a)
Prothrombin is an inactive plasma protein (factor II). Thrombin is the enzyme that converts fibrinogen to fibrin. Fibrin forms the clot threads. Correct: A–III, B–II, C–I.

Q84. Identify the correct statements regarding RBCs:
(i) Formed in the red bone marrow in adults.
(ii) Biconcave in shape and devoid of nucleus in most mammals.
(iii) Average life span is 120 days.
(iv) Destroyed in the liver.

Correct Answer: (a)
RBCs are formed in red bone marrow, are biconcave and enucleated in mammals, and live about 120 days. They are destroyed primarily in the spleen, not the liver. So (i), (ii), (iii) are correct; (iv) is false.

Q85. Match the nodal tissues with their roles/locations:

Column-I	Column-II
A. SAN	(I) Pace-setter (transmits to entire musculature)
B. AVN	(II) Right upper corner of right atrium
C. Purkinje fibres	(III) Lower left corner of right atrium
D. Bundle of His	(IV) Minute fibres throughout ventricles

Correct Answer: (a)
SAN is located at the right upper corner of the right atrium. AVN is at the lower left corner of the right atrium. Purkinje fibres are minute fibres spread throughout the ventricles. The Bundle of His transmits impulses from AVN to ventricles. The given matching A–II, B–III, C–IV, D–I is the conventional pairing in this context.

Q86. Which blood group is called the 'universal donor'?

Correct Answer: (d)
Group O individuals lack both A and B antigens on their RBCs, so their blood can be donated to any ABO group without causing an immune reaction. However, they can only receive group O blood. Group AB is the universal recipient because they have no antibodies against A or B.

Q87. Assertion: Hepatic portal vein carries blood from intestine to liver. Reason: It is a unique vascular connection between the digestive tract and liver.

Correct Answer: (a)
The hepatic portal vein transports nutrient-rich blood from the intestines to the liver, where it is processed and detoxified. This is a specialised connection distinct from other veins. The reason highlights the uniqueness of this vascular pathway and correctly explains the assertion.

Q88. The condition 'erythroblastosis foetalis' occurs due to incompatibility of which factor?

Correct Answer: (b)
Erythroblastosis foetalis (haemolytic disease of the newborn) results from Rh incompatibility between an Rh-negative mother and an Rh-positive fetus. The mother's immune system produces anti-Rh antibodies that cross the placenta and destroy fetal RBCs. ABO incompatibility can cause problems but rarely this severe.

Q89. Match the heart valves with their locations:

Column-I	Column-II
A. Tricuspid valve	(I) Between left atrium and left ventricle
B. Bicuspid (Mitral)	(II) Between right atrium and right ventricle
C. Semilunar valves	(III) Opening of ventricles into PA/Aorta

Correct Answer: (a)
The tricuspid valve is at the right AV opening (between right atrium and right ventricle). The bicuspid (mitral) valve is at the left AV opening. Semilunar valves are at the bases of the pulmonary artery and aorta. Correct: A–II, B–I, C–III.

Q90. Regarding heart anatomy:
(i) Bicuspid valve is also called Mitral valve.
(ii) Tricuspid valve has three flaps.
(iii) Atrio-ventricular septum is thick and fibrous.
(iv) Chordae tendineae are mentioned in the diagram (Fig 15.2).

Correct Answer: (a)
The bicuspid valve is also known as the mitral valve. The tricuspid valve has three cusps. The AV septum is thick and fibrous, and chordae tendineae are present. All statements are correct.

Q91. Which of the following phylum/group matches its circulatory system correctly?
(i) Sponges – Water circulation through body cavities.
(ii) Arthropods – Open circulatory system.
(iii) Annelids – Closed circulatory system.
(iv) Fishes – 3-chambered heart.

Correct Answer: (a)
Sponges circulate water through their body. Arthropods have open systems, annelids have closed. Fishes have 2-chambered hearts, not 3. Thus (i),(ii),(iii) correct; (iv) false.

Q92. Which of the following is correct?
(i) Alfonso Corti studied the auditory system.
(ii) He discovered the organ of Corti in 1851.
(iii) Mammalian RBCs are mostly biconcave.

Correct Answer: (a)
Alfonso Corti is known for his work on the auditory system and discovered the organ of Corti in 1851. Mammalian RBCs are indeed biconcave. All statements are correct.

Q93. ABO grouping is based on the presence or absence of two surface ______ on the RBCs.

Correct Answer: (b)
The ABO blood group system is determined by the presence of antigens A and B on the surface of red blood cells. Plasma contains corresponding antibodies (anti-A and anti-B) that react with foreign antigens. This antigen-antibody interaction is the basis for transfusion compatibility.

Q94. Match the cell characteristics:

Cell	Feature
A. RBCs	(I) Nucleated
B. WBCs	(II) Biconcave
C. Platelets	(III) Fragments

Correct Answer: (a)
RBCs are biconcave. WBCs are nucleated. Platelets are cell fragments. Correct: A–II, B–I, C–III.

Q95. In an ECG, the P-wave represents:

Correct Answer: (c)
The P-wave in an electrocardiogram corresponds to the depolarisation (electrical excitation) of the atria, which triggers atrial contraction. Ventricular depolarisation is shown by the QRS complex, and the T-wave represents ventricular repolarisation. Atrial repolarisation is masked by the QRS complex.

Q96. Assertion: Basophils are involved in inflammatory reactions. Reason: They secrete histamine, serotonin, and heparin.

Correct Answer: (a)
Basophils release histamine, serotonin, and heparin, which are mediators of inflammation and allergic responses. Histamine dilates blood vessels and increases permeability, while heparin prevents clotting. These secretions directly explain basophils' role in inflammation, making the reason correct.

Q97. Select correct statements for 'Double Circulation':
(i) Pulmonary circulation involves right ventricle to lungs to left atrium.
(ii) Systemic circulation involves left ventricle to body to right atrium.
(iii) Deoxygenated blood is carried by systemic arteries.

Correct Answer: (a)
Pulmonary circulation: right ventricle → lungs → left atrium. Systemic: left ventricle → body → right atrium. Systemic arteries carry oxygenated blood, not deoxygenated. So (i) and (ii) correct; (iii) false.

Q98. Atherosclerosis is another name for:

Correct Answer: (c)
Atherosclerosis is the underlying condition of coronary artery disease (CAD), where fatty deposits (plaques) build up inside the coronary arteries, narrowing them and reducing blood flow. Angina is a symptom of CAD, heart failure is a consequence, and cardiac arrest is a sudden stop of heart function.

Q99. Identify correct features of the 'Cardiac Output':
(i) Stroke volume × heart rate.
(ii) Averages 5000 mL (5 litres) in a healthy individual.
(iii) Cannot be altered by the body.
(iv) Higher in athletes.

Correct Answer: (a)
Cardiac output = stroke volume × heart rate, averages ~5 L/min, and is higher in athletes. It is not fixed; it can be altered by sympathetic/parasympathetic stimulation and exercise. So (i),(ii),(iv) correct; (iii) false.

Q100. Assertion: Left ventricle pumps oxygenated blood into the aorta. Reason: This is part of systemic circulation.

Correct Answer: (a)
The left ventricle ejects oxygen-rich blood into the aorta, which distributes it to all body tissues. This forms the systemic circulation. The reason correctly categorises this action and directly explains the assertion.