Explain human respiratory system with a labeled description. (NCERT Class 10 – Important)

Answer: Air enters nostrils→nasal cavity→trachea→bronchi→bronchioles→alveoli. Alveoli are thin‑walled sacs with capillaries where O₂ diffuses into blood and CO₂ diffuses out. Diaphragm and intercostal muscles cause inhalation (thoracic volume ↑) and exhalation (volume ↓).