The diagrams show sections through three blood vessels, which are not drawn to the same scale. Some red blood cells are shown in vessel 3. In which order will red blood cells flow through these vessels when travelling from the right ventricle to the left atrium of the heart?
A) 1 → 2 → 3
B) 1 → 3 → 2
C) 2 → 3 → 1
D) 3 → 1 → 2
▶️ Answer/Explanation
Ans: B (1 → 3 → 2)
The correct sequence follows the pulmonary circulation pathway:
- Vessel 1: Pulmonary artery (carries deoxygenated blood from right ventricle to lungs)
- Vessel 3: Capillaries (site of gas exchange where RBCs become oxygenated)
- Vessel 2: Pulmonary vein (returns oxygenated blood to left atrium)
Key points: The presence of RBCs in vessel 3 confirms it as capillaries, while vessel 1’s thick wall indicates an artery. Vessel 2’s thin wall matches vein characteristics.
The diagram shows blood vessels entering and leaving some organs in the human body.
Which row identifies the pulmonary artery and the renal vein?
▶️ Answer/Explanation
Ans: A
The pulmonary artery carries deoxygenated blood from the heart to the lungs (vessel X), while the renal vein carries filtered blood away from the kidneys (vessel W).
Option A correctly identifies:
- X as pulmonary artery (only artery carrying deoxygenated blood)
- W as renal vein (carrying blood from kidneys to vena cava)
Other options are incorrect because they either reverse these vessels or misidentify Y (aorta) or Z (vena cava) as the target vessels.