1. Which component of blood is responsible for clotting?
a) Red blood cells
b) White blood cells
c) Platelets
d) Plasma
Answer: c) Platelets
2. What is the main function of the circulatory system?
a) To digest food
b) To transport oxygen and nutrients
c) To excrete waste
d) To produce hormones
Answer: b) To transport oxygen and nutrients
3. Which blood vessels carry blood away from the heart?
a) Veins
b) Capillaries
c) Arteries
d) Venules
Answer: c) Arteries
4. Which part of the heart receives deoxygenated blood from the body?
a) Left atrium
b) Right atrium
c) Left ventricle
d) Right ventricle
Answer: b) Right atrium
5. What is the largest artery in the human body?
a) Pulmonary artery
b) Aorta
c) Carotid artery
d) Coronary artery
Answer: b) Aorta
6. Which type of blood vessel allows exchange of materials between blood and tissues?
a) Arteries
b) Veins
c) Capillaries
d) Arterioles
Answer: c) Capillaries
7. What component of blood carries oxygen?
a) Plasma
b) Platelets
c) Red blood cells
d) White blood cells
Answer: c) Red blood cells
8. Which chamber of the heart pumps oxygenated blood to the body?
a) Left atrium
b) Right atrium
c) Left ventricle
d) Right ventricle
Answer: c) Left ventricle
9. Hemoglobin is a protein found in:
a) Plasma
b) White blood cells
c) Red blood cells
d) Platelets
Answer: c) Red blood cells
10. What prevents the backflow of blood in veins?
a) Valves
b) Muscles
c) Artery walls
d) Capillaries
Answer: a) Valves
11. Which part of the circulatory system carries deoxygenated blood to the lungs?
a) Pulmonary vein
b) Pulmonary artery
c) Aorta
d) Vena cava
Answer: b) Pulmonary artery
12. Which is the liquid portion of blood?
a) Serum
b) Plasma
c) Platelets
d) Hemoglobin
Answer: b) Plasma
13. Which blood cells fight infections in the body?
a) Red blood cells
b) Platelets
c) White blood cells
d) Plasma cells
Answer: c) White blood cells
14. What is the rhythmic contraction of the heart called?
a) Circulation
b) Heartbeat
c) Blood flow
d) Pulmonary pulse
Answer: b) Heartbeat
15. Which vein brings deoxygenated blood from the upper body to the heart?
a) Pulmonary vein
b) Superior vena cava
c) Inferior vena cava
d) Coronary vein
Answer: b) Superior vena cava
16. Which is the smallest type of blood vessel?
a) Artery
b) Vein
c) Capillary
d) Arteriole
Answer: c) Capillary
17. Which organ regulates the number of red blood cells in the blood?
a) Liver
b) Heart
c) Kidney
d) Spleen
Answer: c) Kidney
18. Which blood type is known as the universal donor?
a) A
b) B
c) AB
d) O
Answer: d) O
19. Which blood type is considered the universal recipient?
a) A
b) B
c) AB
d) O
Answer: c) AB
20. What is the function of platelets?
a) Carry oxygen
b) Fight infections
c) Clot blood
d) Transport hormones
Answer: c) Clot blood
21. Which layer of the heart wall is muscular and responsible for contraction?
a) Endocardium
b) Myocardium
c) Epicardium
d) Pericardium
Answer: b) Myocardium
22. Which part of the heart receives oxygenated blood from the lungs?
a) Left atrium
b) Right atrium
c) Left ventricle
d) Right ventricle
Answer: a) Left atrium
23. Which is the main vein that carries blood from the lower part of the body to the heart?
a) Superior vena cava
b) Inferior vena cava
c) Pulmonary vein
d) Coronary vein
Answer: b) Inferior vena cava
24. Which structure prevents blood from flowing backward into the atria?
a) Veins
b) Valves
c) Capillaries
d) Arteries
Answer: b) Valves
25. The pacemaker of the heart is called:
a) AV node
b) SA node
c) Bundle of His
d) Purkinje fibers
Answer: b) SA node
26. What is the main function of veins?
a) Carry blood away from the heart
b) Carry blood to the heart
c) Exchange nutrients and gases
d) Pump blood
Answer: b) Carry blood to the heart
27. Which of the following is NOT a component of blood?
a) Plasma
b) Hemoglobin
c) Red blood cells
d) Platelets
Answer: b) Hemoglobin (it’s a protein inside RBCs, not a separate component)
28. Blood pressure is highest in:
a) Veins
b) Arteries
c) Capillaries
d) Venules
Answer: b) Arteries
29. Coronary arteries supply blood to:
a) Lungs
b) Heart muscle
c) Brain
d) Kidneys
Answer: b) Heart muscle
30. The systemic circulation carries blood:
a) Between heart and lungs
b) Between heart and body
c) Within the heart only
d) Between kidneys and liver
Answer: b) Between heart and body