Part 4: Circulatory Pathways (25 MCQs)

Q1. Which type of circulatory system is found in arthropods and most molluscs?

A. Open circulation
B. Closed circulation
C. Single circulation
D. Double circulation

Answer: A

Explanation:

A. Correct: Arthropods/molluscs → open circulation (blood bathes tissues directly).
B. Incorrect: Closed circulation in annelids, vertebrates.
C. Incorrect: Single circulation refers to fish.
D. Incorrect: Double circulation in mammals/birds.

Q2. Which animal group shows closed circulation?

A. Insects
B. Annelids
C. Crustaceans
D. Sponges

Answer: B

Explanation:

A. Incorrect: Insects = open circulation.
B. Correct: Annelids (e.g., earthworm) = closed circulation.
C. Incorrect: Crustaceans = open system.
D. Incorrect: Sponges have no true circulation.

Q3. Which statement is true about open circulation?

A. Blood flows through arteries, veins, capillaries
B. Hemolymph directly bathes tissues
C. Oxygen transport is highly efficient
D. Blood never leaves vessels

Answer: B

Explanation:

A. Incorrect: That is closed circulation.
B. Correct: Hemolymph bathes tissues directly.
C. Incorrect: Open system is less efficient.
D. Incorrect: Blood leaves vessels in open system.

Q4. Which type of circulation is seen in fish?

A. Open circulation
B. Double circulation
C. Single circulation
D. Mixed circulation

Answer: C

Explanation:

A. Incorrect: Fish have closed circulation.
B. Incorrect: Double circulation in mammals/birds.
C. Correct: Fish → heart pumps blood once through gills, then to body.
D. Incorrect: Not mixed.

Q5. How many chambers are present in a fish heart?

A. Two
B. Three
C. Four
D. Five

Answer: A

Explanation:

A. Correct: Fish heart = 2 chambers (1 atrium + 1 ventricle).
B. Incorrect: Amphibians have 3.
C. Incorrect: Birds/mammals have 4.
D. Incorrect: Not five.

Q6. Amphibians and reptiles (except crocodiles) show:

A. Double circulation with complete separation
B. Single circulation
C. Incomplete double circulation (mixed blood)
D. Open circulation

Answer: C

Explanation:

A. Incorrect: Complete separation only in birds/mammals.
B. Incorrect: Single circulation in fish.
C. Correct: Amphibians/reptiles (except crocodiles) → 3-chambered heart → incomplete double circulation.
D. Incorrect: Not open.

Q7. Birds and mammals show:

A. Incomplete double circulation
B. Complete double circulation
C. Single circulation
D. Open circulation

Answer: B

Explanation:

A. Incorrect: Amphibians/reptiles show incomplete.
B. Correct: Birds/mammals → 4-chambered heart → complete double circulation.
C. Incorrect: Fish have single circulation.
D. Incorrect: Not open.

Q8. In single circulation, blood passes through the heart:

A. Once during one complete cycle
B. Twice during one complete cycle
C. Only when oxygenated
D. Only when deoxygenated

Answer: A

Explanation:

A. Correct: Fish (single circulation) → blood passes heart once per cycle.
B. Incorrect: Twice = double circulation.
C. Incorrect: Both oxygenated/deoxygenated phases present.
D. Incorrect: Both types occur.

Q9. In double circulation, blood passes through the heart:

A. Once in each cycle
B. Twice in each cycle
C. Three times in each cycle
D. Continuously without cycle

Answer: B

Explanation:

A. Incorrect: That’s single circulation.
B. Correct: Double circulation → pulmonary + systemic circuits.
C. Incorrect: Not three.
D. Incorrect: Circulation has cycles.

Q10. Which animal has a 3-chambered heart?

A. Crocodile
B. Frog
C. Bird
D. Human

Answer: B

Explanation:

A. Incorrect: Crocodile = 4 chambers.
B. Correct: Frog = 3 chambers (2 atria + 1 ventricle).
C. Incorrect: Birds = 4 chambers.
D. Incorrect: Humans = 4 chambers.

Q11. Which reptile has a 4-chambered heart?

A. Lizard
B. Snake
C. Crocodile
D. Turtle

Answer: C

Explanation:

A. Incorrect: Lizard = 3 chambers.
B. Incorrect: Snake = 3 chambers.
C. Correct: Crocodile = 4 chambers → complete separation.
D. Incorrect: Turtle = 3 chambers.

Q12. Which of the following ensures separation of oxygenated and deoxygenated blood in humans?

A. Valves
B. Four-chambered heart
C. Coronary arteries
D. Blood pressure

Answer: B

Explanation:

A. Incorrect: Valves prevent backflow, not separation.
B. Correct: Four chambers ensure complete separation.
C. Incorrect: Coronary arteries supply the heart muscle.
D. Incorrect: Pressure alone doesn’t separate blood.

Q13. Pulmonary circulation carries blood from:

A. Heart → Body → Heart
B. Heart → Lungs → Heart
C. Lungs → Body → Heart
D. Heart → Brain → Heart

Answer: B

Explanation:

A. Incorrect: That’s systemic circulation.
B. Correct: Pulmonary = heart → lungs → heart.
C. Incorrect: Not correct pathway.
D. Incorrect: Brain is part of systemic.

Q14. Systemic circulation carries blood from:

A. Heart → Body → Heart
B. Heart → Lungs → Heart
C. Lungs → Heart → Body
D. Heart → Kidney → Heart

Answer: A

Explanation:

A. Correct: Systemic circulation = oxygenated blood → body → deoxygenated blood → heart.
B. Incorrect: Pulmonary pathway.
C. Incorrect: Incomplete description.
D. Incorrect: Kidney is just one organ.

Q15. Which is a characteristic feature of closed circulation?

A. Blood directly bathes organs
B. Blood flows only inside vessels
C. Less efficient oxygen transport
D. Found in insects

Answer: B

Explanation:

A. Incorrect: Open system.
B. Correct: Closed → blood confined to vessels.
C. Incorrect: It is more efficient, not less.
D. Incorrect: Insects = open circulation.

Q16. Which statement is true for open circulation?

A. Found in annelids
B. Found in insects
C. Found in mammals
D. Found in fish

Answer: B

Explanation:

A. Incorrect: Annelids = closed circulation.
B. Correct: Insects (arthropods) = open system.
C. Incorrect: Mammals = closed circulation.
D. Incorrect: Fish = single closed circulation.

Q17. Which vessel carries oxygenated blood in pulmonary circulation?

A. Pulmonary artery
B. Pulmonary vein
C. Vena cava
D. Coronary vein

Answer: B

Explanation:

A. Incorrect: Pulmonary artery carries deoxygenated blood.
B. Correct: Pulmonary vein carries oxygenated blood from lungs to heart.
C. Incorrect: Vena cava carries deoxygenated systemic blood.
D. Incorrect: Coronary vein drains heart.

Q18. In systemic circulation, which vessel carries deoxygenated blood back to the heart?

A. Aorta
B. Pulmonary vein
C. Vena cava
D. Coronary artery

Answer: C

Explanation:

A. Incorrect: Aorta carries oxygenated blood.
B. Incorrect: Pulmonary vein carries oxygenated blood.
C. Correct: Vena cava → deoxygenated blood to right atrium.
D. Incorrect: Coronary artery supplies oxygenated blood.

Q19. Coronary circulation refers to:

A. Heart → Brain → Heart
B. Circulation of blood within heart muscles
C. Heart → Lungs → Heart
D. Heart → Kidneys → Heart

Answer: B

Explanation:

A. Incorrect: Brain circulation = cerebral.
B. Correct: Coronary circulation = supplies myocardium with blood.
C. Incorrect: That is pulmonary.
D. Incorrect: That is renal circulation.

Q20. Which vessel carries oxygenated blood from heart to body?

A. Pulmonary artery
B. Pulmonary vein
C. Aorta
D. Vena cava

Answer: C

Explanation:

A. Incorrect: Pulmonary artery carries deoxygenated blood.
B. Incorrect: Pulmonary vein carries blood to heart.
C. Correct: Aorta distributes oxygenated blood to body.
D. Incorrect: Vena cava returns deoxygenated blood.

Q21. Which vessel carries deoxygenated blood from heart to lungs?

A. Pulmonary artery
B. Pulmonary vein
C. Aorta
D. Coronary vein

Answer: A

Explanation:

A. Correct: Pulmonary artery carries deoxygenated blood to lungs.
B. Incorrect: Pulmonary vein carries oxygenated blood.
C. Incorrect: Aorta carries oxygenated blood.
D. Incorrect: Coronary vein drains myocardium.

Q22. Which of the following is the correct sequence in pulmonary circulation?

A. Right atrium → Right ventricle → Lungs → Left atrium
B. Left atrium → Left ventricle → Lungs → Right atrium
C. Right atrium → Lungs → Left ventricle → Right ventricle
D. Left ventricle → Lungs → Right atrium → Left atrium

Answer: A

Explanation:

A. Correct: Right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium.
B. Incorrect: Left atrium doesn’t start pulmonary circulation.
C. Incorrect: Wrong order.
D. Incorrect: Wrong chambers.

Q23. Which circulation supplies oxygen to the heart muscles themselves?

A. Pulmonary
B. Systemic
C. Coronary
D. Portal

Answer: C

Explanation:

A. Incorrect: Pulmonary = lungs.
B. Incorrect: Systemic = whole body.
C. Correct: Coronary arteries → myocardium.
D. Incorrect: Portal = gut → liver.

Q24. The hepatic portal system carries blood from:

A. Kidney → Heart
B. Liver → Heart
C. Digestive tract → Liver
D. Heart → Brain

Answer: C

Explanation:

A. Incorrect: Kidney → systemic circulation.
B. Incorrect: Liver drains into hepatic vein.
C. Correct: Hepatic portal system = digestive tract → liver.
D. Incorrect: Brain → cerebral circulation.

Q25. Advantage of double circulation is:

A. Mixing of oxygenated and deoxygenated blood
B. Complete separation ensures efficient oxygen supply
C. Lower blood pressure in tissues
D. Simpler system

Answer: B

Explanation:

A. Incorrect: Mixing reduces efficiency.
B. Correct: Double circulation → complete separation, high efficiency.
C. Incorrect: Blood pressure remains high.
D. Incorrect: It is complex but efficient.

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Part 4: Circulatory Pathways (25 MCQs)