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[HAP-04] Respiratory System Anatomy, Spirometry, Gas Exchange & Acid–Base Regulation
HAP-04 • 1. Anatomy & PhysiologyLearning Objectives
Trace the tracheobronchial tree (generations 0–23), Type I vs Type II pneumocytes (surfactant dipalmitoylphosphatidylcholine), and autonomic bronchial tone.; Distinguish obstructive (Asthma vs COPD: FEV1/FVC < 0.70, bronchodilator reversibility ≥ 12% and ≥ 200 mL) from restrictive lung disease on spirometry.; Interpret the Oxygen–Haemoglobin Dissociation Curve (Bohr effect, 2,3-BPG) and arterial blood gas (ABG) disorders.
Chapter Overview & Core Explanation
The lungs bring inhaled oxygen across a 70-square-metre alveolar membrane into red blood cells while expelling carbon dioxide. In asthma and COPD, smooth muscle spasm and mucosal swelling narrow the airways, making exhalation slow and difficult.
Key Exam & Clinical Takeaways
- A rightward shift of the Oxygen–Haemoglobin Dissociation Curve ('CADET, face right': ↑CO2, ↑Acid/↓pH, ↑2,3-DPG, ↑Exercise, ↑Temperature) facilitates oxygen unloading to metabolically active tissues.
- Antenatal [7.20] Dexamethasone or [7.23] Betamethasone stimulates fetal Type II pneumocytes to synthesize lecithin (dipalmitoylphosphatidylcholine) surfactant.