Ijmb Model Questions Vol1 2025 Biology Question 4

Practice essay / theory question 4 from the 2025 Ijmb Model Questions Vol1 Biology examination. This question covers respiration, gas exchange, ventilation‑perfusion .

Ijmb Model Questions Vol1 2025 Biology Essay / Theory
Topics: respiration gas exchange ventilation‑perfusion
Question 4 IJMB_MODEL_QUESTIONS_VOL1 • 2025 • BIOLOGY • essay

The diagram shows the human respiratory system with the labelled components A–I. A – Nasal cavity B – Pharynx C – Larynx D – Trachea E – Primary bronchi F – Bronchioles G – Alveolar sac H – Pulmonary capillary network I – Diaphragm

Question Parts

( a )
Describe the complete pathway that air follows from the external environment to the site of gas exchange, naming each structure it passes through.
( b )
The partial pressure of oxygen in ambient air at sea level is 160 mmHg. Assuming water‑vapour pressure in the conducting airways is 47 mmHg and using the alveolar gas equation PAO₂ = FiO₂(PB – PH₂O) – (PaCO₂ / R) where FiO₂ = 0.21, PB = 760 mmHg, PaCO₂ = 40 mmHg and R = 0.8, calculate the alveolar oxygen partial pressure (PAO₂). Show all steps and state any assumptions made.
( c )
Using the diagram, explain how the structure of the alveolar wall promotes efficient gas exchange. Mention at least three distinct structural features.
( d )
A patient exhibits a ventilation‑perfusion (V/Q) mismatch in which 30 % of alveoli are perfused but not ventilated. Discuss the effect of this mismatch on arterial oxygen tension and propose one physiological compensation mechanism that the body may employ.

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About This Question

This is Ijmb Model Questions Vol1 2025 Biology Question 4. It is one of the essay questions from the 2025 Ijmb Model Questions Vol1 Biology examination.

The question covers respiration, gas exchange, ventilation‑perfusion .

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