Trace the complete pathway of air from the nostrils to the alveoli in human beings, naming each structure the air passes through. State one structural feature of the alveoli that makes them efficient for gas exchange.
Generated by claude-sonnet-4-6 · 2026-06-26 00:59 · grounding rag
Model Answer
Pathway of air from nostrils to alveoli:
Nostrils → Nasal passage (filtered by fine hairs and mucus) → Throat (pharynx/larynx) → Trachea (supported by cartilage rings) → Bronchi → Bronchioles → Alveoli
Structural feature of alveoli:
The alveoli have walls containing an extensive network of blood capillaries. This, combined with their balloon-like structure that provides a very large surface area (about 80 m²), makes them highly efficient for gas exchange.
Source: Chapter 5, Section 5.3 — Respiration
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Explanation
- Examiners expect each structure named in order — missing any (e.g., bronchi or bronchioles) loses marks.
- The one structural feature asked is the rich network of blood capillaries in the thin alveolar walls; mentioning the large surface area is a bonus point.
- The passage explicitly states "rings of cartilage in the throat" keep the airway open — you can mention this for trachea.
- Do not write a lengthy paragraph; a labelled pathway + one clear sentence on the structural feature is sufficient for 3 marks.