Respiratory Mechanics and Gas Exchange · USMLE Step 1

Which feature of the alveolar–capillary membrane optimizes efficient gas exchange under normal conditions?

  1. Thick, multi-layered walls and low surface area
  2. Thin membrane, large surface area, dense capillaries
  3. High airway resistance and low perfusion
  4. Minimal capillary network to reduce diffusion distance
Show answer and explanation

Correct answer: Thin membrane, large surface area, dense capillaries

Efficient gas exchange requires a thin respiratory membrane to minimize diffusion distance and a large alveolar surface area with dense capillary network to maximize gas exchange capacity.

Difficulty: Medium Question 20 of 20

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