1. The human circulatory system is also known as the___________.
A) Nervous system
B) Respiratory system
C) Cardiovascular system
D) Digestive system
Answer: C
Explanation: The circulatory system consists of the heart, blood, and blood vessels, collectively called the cardiovascular system.
2. What is the average volume of blood in an adult human?
A) 1–2 liters
B) 3–4 liters
C) 4–6 liters
D) 8–10 liters
Answer: C
Explanation: A healthy adult has about 4–6 liters of blood, depending on sex, age, and body size.
3. What is the normal pH of human blood?
A) 6.8
B) 7.0
C) 7.4
D) 8.0
Answer: C
Explanation: Blood is slightly alkaline with a normal pH of about 7.35–7.45.
4. Which component of blood is responsible for oxygen transport?
A) Platelets
B) Plasma
C) White blood cells
D) Red blood cells
Answer: D
Explanation: RBCs contain hemoglobin, which binds to oxygen for transport.
5. Hemoglobin is a___________.
A) Protein
B) Fat
C) Carbohydrate
D) Vitamin
Answer: A
Explanation: Hemoglobin is a conjugated protein with iron, responsible for carrying oxygen.
6. The average lifespan of human red blood cells is___________.
A) 60 days
B) 90 days
C) 120 days
D) 150 days
Answer: C
Explanation: RBCs live for about 120 days before being broken down in the spleen.
7. Which blood cells are called “soldiers of the body”?
A) RBCs
B) WBCs
C) Platelets
D) Plasma
Answer: B
Explanation: WBCs protect the body against infections and foreign substances.
8. Which cells are responsible for blood clotting?
A) RBCs
B) WBCs
C) Platelets
D) Neutrophils
Answer: C
Explanation: Platelets release clotting factors that help in blood coagulation.
9. What is the liquid portion of blood called?
A) Serum
B) Plasma
C) Cytoplasm
D) Lymph
Answer: B
Explanation: Plasma is the straw-colored liquid that transports nutrients, hormones, and waste.
10. Which vitamin is essential for blood clotting?
A) Vitamin A
B) Vitamin B12
C) Vitamin C
D) Vitamin K
Answer: D
Explanation: Vitamin K is necessary for the synthesis of prothrombin, a clotting factor.
11. Which organ is called the “graveyard of RBCs”?
A) Liver
B) Kidney
C) Spleen
D) Lungs
Answer: C
Explanation: The spleen destroys old and damaged RBCs.
12. Which type of WBC is most abundant in human blood?
A) Basophils
B) Eosinophils
C) Neutrophils
D) Lymphocytes
Answer: C
Explanation: Neutrophils form 60–70% of WBCs and fight bacterial infections.
13. Which blood group is called the universal donor?
A) A+
B) AB+
C) O–
D) AB–
Answer: C
Explanation: O– blood can be given to any group in emergencies, as it lacks A, B, and Rh antigens.
14. Which blood group is known as the universal recipient?
A) O+
B) A+
C) AB+
D) B+
Answer: C
Explanation: AB+ individuals can receive blood from any group due to the presence of all antigens.
15. The Rh factor is named after which animal?
A) Rabbit
B) Rat
C) Rhesus monkey
D) Rhinoceros
Answer: C
Explanation: Rh factor was first discovered in rhesus monkeys.
16. Which protein in plasma helps in defense?
A) Albumin
B) Globulin
C) Fibrinogen
D) Myosin
Answer: B
Explanation: Globulins act as antibodies in immune defense.
17. Which component helps maintain osmotic balance in blood?
A) Hemoglobin
B) Albumin
C) Globulin
D) Platelets
Answer: B
Explanation: Albumin regulates osmotic pressure and prevents fluid loss from blood vessels.
18. Which blood cells lack a nucleus in humans?
A) WBCs
B) RBCs
C) Platelets
D) Monocytes
Answer: B
Explanation: Mature RBCs lack nuclei to maximize oxygen-carrying space.
19. Which condition is caused by low hemoglobin?
A) Leukemia
B) Anemia
C) Hemophilia
D) Jaundice
Answer: B
Explanation: Anemia is due to insufficient RBCs or hemoglobin.
20. Which clotting factor is also called anti-hemophilic factor?
A) Factor I
B) Factor VIII
C) Factor IX
D) Factor X
Answer: B
Explanation: Deficiency of Factor VIII causes hemophilia A.
21. What is lymph?
A) Plasma without RBCs
B) Plasma without clotting factors
C) Tissue fluid in lymphatic vessels
D) Blood without platelets
Answer: C
Explanation: Lymph is colorless fluid that transports fats and immune cells.
22. What is the major function of lymph nodes?
A) Filter urine
B) Produce insulin
C) Trap pathogens
D) Digest fats
Answer: C
Explanation: Lymph nodes act as filters and activate immune responses.
23. Which metal is present in hemoglobin?
A) Magnesium
B) Iron
C) Copper
D) Zinc
Answer: B
Explanation: Each hemoglobin molecule has iron ions in heme groups that bind oxygen.
24. Which pigment gives red color to blood?
A) Chlorophyll
B) Hemocyanin
C) Hemoglobin
D) Bilirubin
Answer: C
Explanation: Hemoglobin gives red color due to its iron-porphyrin complex.
25. Which blood disorder is characterized by abnormal crescent-shaped RBCs?
A) Thalassemia
B) Leukemia
C) Sickle cell anemia
D) Hemophilia
Answer: C
Explanation: Caused by genetic mutation in hemoglobin, RBCs become sickle-shaped.
26. The human heart is located in the___________.
A) Abdominal cavity
B) Thoracic cavity
C) Cranial cavity
D) Pelvic cavity
Answer: B
Explanation: The heart lies in the thoracic cavity, between the lungs, slightly tilted to the left.
27. The human heart is surrounded by a protective sac called___________.
A) Pleura
B) Pericardium
C) Peritoneum
D) Meninges
Answer: B
Explanation: The pericardium is a double-walled sac filled with pericardial fluid to reduce friction during heartbeats.
28. How many chambers are present in the human heart?
A) Two
B) Three
C) Four
D) Five
Answer: C
Explanation: The human heart has four chambers – two atria (upper) and two ventricles (lower).
29. Which chamber of the heart receives deoxygenated blood from the body?
A) Left atrium
B) Right atrium
C) Left ventricle
D) Right ventricle
Answer: B
Explanation: The right atrium receives deoxygenated blood from the superior and inferior vena cava.
30. Which chamber pumps oxygenated blood to the body?
A) Right atrium
B) Right ventricle
C) Left atrium
D) Left ventricle
Answer: D
Explanation: The left ventricle pumps oxygenated blood to the whole body via the aorta.
31. Which blood vessels carry blood from the heart to the lungs?
A) Pulmonary veins
B) Pulmonary arteries
C) Coronary arteries
D) Aorta
Answer: B
Explanation: Pulmonary arteries carry deoxygenated blood from the right ventricle to the lungs.
32. Which blood vessels bring oxygenated blood from the lungs to the heart?
A) Pulmonary veins
B) Pulmonary arteries
C) Coronary veins
D) Vena cava
Answer: A
Explanation: Pulmonary veins carry oxygenated blood into the left atrium.
33. Which valve prevents backflow of blood from the right ventricle to the right atrium?
A) Bicuspid valve
B) Tricuspid valve
C) Semilunar valve
D) Aortic valve
Answer: B
Explanation: The tricuspid valve is located between the right atrium and right ventricle.
34. The bicuspid valve is also called___________.
A) Aortic valve
B) Mitral valve
C) Pulmonary valve
D) Coronary valve
Answer: B
Explanation: The bicuspid valve (mitral valve) is between the left atrium and left ventricle.
35. The largest artery in the human body is ___________.
A) Pulmonary artery
B) Carotid artery
C) Coronary artery
D) Aorta
Answer: D
Explanation: The aorta carries oxygen-rich blood from the left ventricle to the entire body.
36. The contraction phase of the heart is called ___________.
A) Diastole
B) Systole
C) Resting
D) Circulation
Answer: B
Explanation: During systole, the heart muscles contract and pump blood.
37. The relaxation phase of the heart is called ___________.
A) Systole
B) Diastole
C) Cardiac arrest
D) Conduction
Answer: B
Explanation: During diastole, the heart chambers relax and fill with blood.
38. The sequence of events in one complete heartbeat is called ___________.
A) Circulation
B) Cardiac cycle
C) Systole
D) Diastole
Answer: B
Explanation: One cardiac cycle includes systole and diastole of atria and ventricles.
39. The average duration of a cardiac cycle in humans is ___________.
A) 0.5 sec
B) 0.8 sec
C) 1.0 sec
D) 1.2 sec
Answer: B
Explanation: At an average heart rate of 75 beats per minute, one cycle lasts 0.8 seconds.
40. The pacemaker of the human heart is ___________.
A) AV node
B) SA node
C) Bundle of His
D) Purkinje fibers
Answer: B
Explanation: The sinoatrial (SA) node initiates the heartbeat and is called the natural pacemaker.
41. Where is the SA node located?
A) Left atrium
B) Right atrium
C) Left ventricle
D) Right ventricle
Answer: B
Explanation: The SA node lies in the wall of the right atrium near the opening of the superior vena cava.
42. The bundle of His is associated with ___________.
A) Hormone secretion
B) Heart conduction system
C) Oxygen transport
D) Blood clotting
Answer: B
Explanation: The bundle of His transmits impulses from the AV node to the ventricles.
43. Which instrument is used to record electrical activity of the heart?
A) EEG
B) ECG
C) MRI
D) X-ray
Answer: B
Explanation: Electrocardiogram (ECG) records electrical impulses during heart activity.
44. “Lub-dub” heart sounds are produced due to ___________.
A) Blood circulation
B) Closing of valves
C) Expansion of atria
D) Contraction of muscles
Answer: B
Explanation: “Lub” is closure of atrioventricular valves; “dub” is closure of semilunar valves.
45. Normal human heartbeat rate is about ___________.
A) 40–50 per minute
B) 60–80 per minute
C) 100–120 per minute
D) 150–200 per minute
Answer: B
Explanation: Average adult heart rate is 72 beats per minute.
46. Which hormone increases heart rate during stress or fear?
A) Insulin
B) Thyroxine
C) Adrenaline
D) Estrogen
Answer: C
Explanation: Adrenaline (epinephrine) stimulates faster heartbeat by acting on the SA node.
47. The blood supply to the heart itself is provided by ___________.
A) Aorta
B) Pulmonary artery
C) Coronary arteries
D) Jugular vein
Answer: C
Explanation: Coronary arteries branch from the aorta and supply oxygen to heart muscles.
48. In heart attack, which blood vessels are blocked?
A) Pulmonary arteries
B) Coronary arteries
C) Jugular veins
D) Carotid arteries
Answer: B
Explanation: Blockage of coronary arteries cuts off oxygen supply to heart muscles, causing myocardial infarction (heart attack).
49. Which condition refers to abnormal rhythm of heartbeat?
A) Tachycardia
B) Bradycardia
C) Arrhythmia
D) Hypertension
Answer: C
Explanation: Arrhythmia refers to irregular heartbeat due to electrical conduction problems.
50. Artificial pacemakers are implanted in patients with malfunctioning ___________.
A) AV node
B) SA node
C) Both SA and AV node
D) Bundle of His
Answer: B
Explanation: Artificial pacemakers regulate heartbeats when the natural SA node fails.
51. The type of blood circulation present in humans is ___________.
A) Single circulation
B) Double circulation
C) Open circulation
D) Mixed circulation
Answer: B
Explanation: Humans have double circulation – pulmonary (heart → lungs → heart) and systemic (heart → body → heart).
52. Which scientist first described blood circulation in humans?
A) Aristotle
B) William Harvey
C) Hippocrates
D) Robert Hooke
Answer: B
Explanation: William Harvey (1628) discovered the circulation of blood and the role of the heart as a pump.
53. Blood circulation between heart and lungs is called ___________.
A) Systemic circulation
B) Pulmonary circulation
C) Coronary circulation
D) Lymph circulation
Answer: B
Explanation: Pulmonary circulation carries deoxygenated blood to the lungs and oxygenated blood back to the heart.
54. Blood circulation between heart and body organs (except lungs) is called ___________.
A) Pulmonary circulation
B) Systemic circulation
C) Coronary circulation
D) Hepatic circulation
Answer: B
Explanation: Systemic circulation provides oxygenated blood to all body tissues.
55. Which circulation supplies blood to the heart muscles themselves?
A) Pulmonary circulation
B) Systemic circulation
C) Coronary circulation
D) Portal circulation
Answer: C
Explanation: Coronary circulation ensures continuous oxygen and nutrients to heart tissues.
56. What is the average blood pressure in humans?
A) 80/60 mmHg
B) 120/80 mmHg
C) 140/100 mmHg
D) 160/120 mmHg
Answer: B
Explanation: Normal blood pressure is systolic 120 mmHg and diastolic 80 mmHg.
57. The instrument used to measure blood pressure is ___________.
A) ECG
B) Spirometer
C) Sphygmomanometer
D) Hygrometer
Answer: C
Explanation: A sphygmomanometer measures systolic and diastolic blood pressure.
58. High blood pressure is also called ___________.
A) Hypotension
B) Hypertension
C) Arrhythmia
D) Angina
Answer: B
Explanation: Hypertension is when blood pressure is persistently above normal, e.g., above 140/90 mmHg.
59. Low blood pressure is called ___________.
A) Hypertension
B) Hypotension
C) Angina
D) Stroke
Answer: B
Explanation: Hypotension is abnormally low blood pressure, causing dizziness and fainting.
60. Which of the following is not a blood vessel?
A) Artery
B) Vein
C) Capillary
D) Neuron
Answer: D
Explanation: Arteries, veins, and capillaries are blood vessels, while neurons are nerve cells.
61. Which blood vessels carry blood away from the heart?
A) Veins
B) Arteries
C) Capillaries
D) Venules
Answer: B
Explanation: Arteries carry blood from the heart to body parts (usually oxygenated blood).
62. Which blood vessels carry blood toward the heart?
A) Arteries
B) Veins
C) Capillaries
D) Arterioles
Answer: B
Explanation: Veins return blood to the heart (usually deoxygenated blood).
63. The smallest blood vessels are ___________.
A) Arteries
B) Veins
C) Capillaries
D) Venules
Answer: C
Explanation: Capillaries are one-cell thick and allow exchange of gases, nutrients, and wastes.
64. Which artery supplies blood to the brain?
A) Jugular artery
B) Carotid artery
C) Coronary artery
D) Pulmonary artery
Answer: B
Explanation: Carotid arteries deliver oxygenated blood to the brain.
65. Which vein carries oxygenated blood?
A) Pulmonary vein
B) Jugular vein
C) Coronary vein
D) Hepatic vein
Answer: A
Explanation: The pulmonary vein carries oxygenated blood from lungs to left atrium.
66. Which artery carries deoxygenated blood?
A) Aorta
B) Coronary artery
C) Pulmonary artery
D) Carotid artery
Answer: C
Explanation: Pulmonary arteries carry deoxygenated blood from right ventricle to lungs.
67. The hepatic portal vein carries blood from ___________.
A) Kidney to liver
B) Intestine to liver
C) Heart to brain
D) Lungs to heart
Answer: B
Explanation: The hepatic portal vein carries nutrient-rich blood from the intestine to the liver.
68. Which condition is caused by narrowing of coronary arteries?
A) Hypertension
B) Angina pectoris
C) Stroke
D) Anemia
Answer: B
Explanation: Angina occurs when blood supply to the heart muscle is reduced, causing chest pain.
69. A sudden blockage of blood flow to the brain causes ___________.
A) Hypertension
B) Stroke
C) Hemophilia
D) Anemia
Answer: B
Explanation: Stroke is caused by interruption of blood flow in brain arteries.
70. Which disease is known as “silent killer”?
A) Diabetes
B) Hypertension
C) Stroke
D) Tuberculosis
Answer: B
Explanation: Hypertension often shows no symptoms until severe damage occurs, hence called the silent killer.
71. Varicose veins are caused by ___________.
A) Bacterial infection
B) Weak valves in veins
C) High blood sugar
D) Lack of hemoglobin
Answer: B
Explanation: Faulty valves cause blood pooling, leading to twisted, enlarged veins.
72. Atherosclerosis is caused by ___________.
A) Parasite infection
B) Deposition of cholesterol in arteries
C) Deficiency of hemoglobin
D) Clotting factor deficiency
Answer: B
Explanation: Atherosclerosis narrows arteries due to fatty deposits (plaques).
73. Hemophilia is a disease related to ___________.
A) RBC deficiency
B) Platelet deficiency
C) Clotting factor deficiency
D) WBC deficiency
Answer: C
Explanation: Hemophilia is a genetic disorder where blood fails to clot properly.
74. Leukemia is also known as ___________.
A) Blood cancer
B) Heart attack
C) Hypertension
D) Stroke
Answer: A
Explanation: Leukemia is uncontrolled proliferation of abnormal white blood cells.
75. Which organ regulates blood pressure by controlling blood volume?
A) Liver
B) Kidney
C) Spleen
D) Pancreas
Answer: B
Explanation: Kidneys regulate blood volume and pressure by controlling water and salt balance.
76. The heartbeat originates due to ___________.
A) Nerve stimulation
B) Hormone secretion
C) Myogenic activity of heart muscles
D) Skeletal muscles
Answer: C
Explanation: The human heart is myogenic; impulses are generated in the SA node without external nerves.
77. The “heart of hearts” (regulating heart rate) is ___________.
A) AV node
B) SA node
C) Purkinje fibers
D) Bundle of His
Answer: B
Explanation: The SA node initiates impulses that control heart rhythm.
78. Which blood vessel is used for pulse measurement at the wrist?
A) Carotid artery
B) Jugular vein
C) Radial artery
D) Ulnar vein
Answer: C
Explanation: Pulse is commonly measured by palpating the radial artery at the wrist.
79. Which artery is most commonly affected in a heart attack?
A) Carotid artery
B) Coronary artery
C) Radial artery
D) Pulmonary artery
Answer: B
Explanation: Blockage of coronary arteries reduces blood flow to heart muscles, causing myocardial infarction.
80. Which condition is characterized by prolonged high blood sugar damaging blood vessels?
A) Diabetes mellitus
B) Atherosclerosis
C) Hypertension
D) Anemia
Answer: A
Explanation: Diabetes damages blood vessels, increasing risk of circulatory diseases.
81. Which artery carries blood to the kidneys?
A) Coronary artery
B) Carotid artery
C) Renal artery
D) Hepatic artery
Answer: C
Explanation: Renal arteries supply blood directly to kidneys.
82. The term “tachycardia” refers to ___________.
A) Slow heartbeat
B) Irregular heartbeat
C) Fast heartbeat
D) Absent heartbeat
Answer: C
Explanation: Tachycardia is a heart rate above 100 beats per minute.
83. The term “bradycardia” refers to ___________.
A) Slow heartbeat
B) Fast heartbeat
C) Irregular heartbeat
D) Absent heartbeat
Answer: A
Explanation: Bradycardia is a heart rate below 60 beats per minute.
84. Which artery is palpated in the neck to check pulse?
A) Carotid artery
B) Jugular vein
C) Subclavian artery
D) Axillary artery
Answer: A
Explanation: Carotid arteries in the neck are used to check pulse, especially in emergencies.
85. What is the function of Purkinje fibers?
A) Supply oxygen to heart
B) Generate impulses in heart
C) Distribute impulses to ventricular walls
D) Close heart valves
Answer: C
Explanation: Purkinje fibers spread conduction signals for coordinated ventricular contraction.
86. Which blood disorder is linked with bone marrow cancer?
A) Anemia
B) Leukemia
C) Hemophilia
D) Thrombocytopenia
Answer: B
Explanation: Leukemia originates in bone marrow due to uncontrolled WBC production.
87. Which type of blood circulation is absent in fishes?
A) Single circulation
B) Double circulation
C) Closed circulation
D) Systemic circulation
Answer: B
Explanation: Fishes have single circulation; blood passes through heart only once in each circuit.
88. “Silent heart attack” often occurs in patients with ___________.
A) Asthma
B) Diabetes
C) Tuberculosis
D) Malaria
Answer: B
Explanation: Diabetes damages nerves, reducing pain sensation during heart attacks.
89. The blood pressure is highest in which blood vessels?
A) Veins
B) Capillaries
C) Arteries
D) Venules
Answer: C
Explanation: Arteries carry blood at high pressure directly pumped from the heart.
90. Which structure prevents backflow of blood inside veins?
A) Muscles
B) Valves
C) Capillaries
D) Nerves
Answer: B
Explanation: Veins contain valves that prevent blood from flowing backward.
91. Which organ produces erythropoietin, a hormone for RBC production?
A) Heart
B) Kidney
C) Liver
D) Spleen
Answer: B
Explanation: Kidneys secrete erythropoietin, which stimulates bone marrow to produce RBCs.
92. Normal cardiac output in a healthy adult is approximately ___________.
A) 1 liter/min
B) 2 liters/min
C) 5 liters/min
D) 10 liters/min
Answer: C
Explanation: Cardiac output = stroke volume × heart rate; about 5 liters/min in adults.
93. Stroke volume refers to ___________.
A) Blood pumped per second
B) Blood pumped per beat
C) Blood pumped per minute
D) Blood pumped per hour
Answer: B
Explanation: Stroke volume is the amount of blood pumped by one ventricle in a single heartbeat.
94. In ECG, the QRS complex represents ___________.
A) Atrial depolarization
B) Ventricular depolarization
C) Ventricular repolarization
D) Atrial repolarization
Answer: B
Explanation: QRS complex indicates depolarization of ventricles (leading to contraction).
95. Which vitamin deficiency causes anemia due to impaired RBC formation?
A) Vitamin A
B) Vitamin B12
C) Vitamin C
D) Vitamin D
Answer: B
Explanation: Vitamin B12 deficiency leads to pernicious anemia.
96. Which blood cells are involved in allergic reactions?
A) Neutrophils
B) Basophils
C) Monocytes
D) Lymphocytes
Answer: B
Explanation: Basophils release histamine, causing allergic responses.
97. “Athlete’s heart” is a condition of ___________.
A) Weak heart muscles
B) Enlarged and strong heart due to exercise
C) Irregular heartbeat
D) Heart failure
Answer: B
Explanation: Regular exercise increases heart muscle mass, improving cardiac efficiency.
98. Which test detects blockage in coronary arteries?
A) EEG
B) ECG
C) Angiography
D) Spirometry
Answer: C
Explanation: Angiography uses dye and X-ray imaging to detect coronary blockages.
99. Which modern surgical technique replaces blocked coronary arteries?
A) Dialysis
B) Bypass surgery
C) Endoscopy
D) Biopsy
Answer: B
Explanation: Coronary bypass surgery restores blood flow by grafting alternate vessels.
100. Which artificial device is used to maintain blood circulation during open-heart surgery?
A) Defibrillator
B) Heart–lung machine
C) Dialysis machine
D) Pacemaker
Answer: B
Explanation: A heart–lung machine temporarily takes over circulation and oxygenation during surgery.