CORE VALUES (Memorise Exactly)

• TV = 500 mL | IRV = 2500–3000 mL | ERV = 1000–1100 mL | RV = 1100–1200 mL
• VC = 3500–4600 mL | TLC = 5000–6000 mL | FRC = 2100–2300 mL
• Alveolar pO2 = 104 mmHg | venous pO2 = 40 mmHg (gradient = 64)
• Venous pCO2 = 45 mmHg | alveolar pCO2 = 40 mmHg (gradient = 5)

TRANSPORT PERCENTAGES

• O2: 97% oxyHb + 3% dissolved
• CO2: 70% HCO3– + 23% carbaminoHb + 7% dissolved (BCD = 70-23-7)

KEY FORMULAS

• VC = TV + IRV + ERV | TLC = VC + RV | FRC = ERV + RV | IC = TV + IRV | EC = TV + ERV

MUSCLES

• Inspiration: Diaphragm (contracts, flattens) + External intercostals (ribs up & out)
• Quiet expiration: PASSIVE (elastic recoil only)
• Forced expiration: Internal intercostals + Abdominals

CONTROL CENTRES

• Medulla = respiratory rhythmicity centre (initiates breathing)
• Pons (pneumotaxic) = limits inspiration duration
• Peripheral chemoreceptors = carotid + aortic bodies (detect pO2, pCO2, H+)

BOHR EFFECT (right shift → more O2 released)

CADET: CO2↑, Acid (H+)↑, DPG↑, Exercise, Temperature↑

DIFFUSION MEMBRANE = 3 LAYERS (EBE)

Alveolar Epithelium → Basement membrane (shared) → Capillary Endothelium

LUNG ANATOMY

• Right lung = 3 lobes | Left lung = 2 lobes (cardiac notch)
• Trachea = C-shaped cartilaginous rings

DISORDERS IN ONE LINE EACH

• Asthma: allergic airway narrowing → wheezing, REVERSIBLE
• Emphysema: alveolar wall destruction → barrel chest, ↑RV, IRREVERSIBLE
• Silicosis: silica dust → fibrosis, dyspnoea (mining)
• Asbestosis: asbestos → fibrosis + mesothelioma risk

NEET NEVER-FORGET RULES

1. RV ≠ FRC (RV = after MAX forced; FRC = after NORMAL expiration)
2. VC excludes RV (TLC includes RV)
3. CO2 = 70% HCO3– (NOT carbaminoHb)
4. Quiet expiration = PASSIVE (no muscles)
5. Right shift = LOWER O2 affinity = MORE O2 released (not retained)