Between the air in an alveolus and the blood, oxygen must cross
Correct answer: B. two cell layers
- A. one cell layer
- B. two cell layers
- C. four cell layers
- D. eight cell layers
Explanation
Only the single alveolar epithelium and the single capillary endothelium stand in the way, a combined thickness of about one micrometre. This minimal barrier is what makes rapid diffusion possible.
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About Human Respiratory System
The human respiratory system conducts air to the alveoli, where oxygen and carbon dioxide exchange occurs across thin respiratory surfaces. Questions cover the nasal passage, trachea, bronchi, lungs, diaphragm and intercostal muscles, ventilation mechanics and gas transport, while distinguishing breathing and gaseous exchange from cellular respiration.
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