Why does a higher ventilation-perfusion ratio in the lung apex, compared to the base, contribute to increased susceptibility to tuberculosis (TB) infection in the apex?

💡 Explanation

The higher ventilation-perfusion ratio in the lung apex means that, although there's more oxygen available, there is relatively less blood flow for immune cell recruitment. Because alveolar macrophages are less active due to reduced perfusion, TB bacteria are not cleared efficiently; therefore, infection is more likely in the apex, rather than being effectively eliminated by immune responses.

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