Gas Exchange at the Alveolus
Lung Volumes and Capacities
| Volume/Capacity | Value (mL) | Formula |
|---|---|---|
| TV | 500 | — |
| IRV | 2500–3000 | — |
| ERV | 1000–1100 | — |
| RV | 1100–1200 | — |
| IC | 3000–3500 | TV + IRV |
| EC | 1500–1600 | TV + ERV |
| FRC | 2100–2300 | ERV + RV |
| VC | 3500–4600 | TV + IRV + ERV |
| TLC | 5000–6000 | VC + RV |
Gas Transport Comparison
| Parameter | O2 Transport | CO2 Transport |
|---|---|---|
| Primary form | Oxyhaemoglobin (97%) | Bicarbonate HCO3– (70%) |
| Secondary form | Dissolved in plasma (3%) | Carbaminohaemoglobin (23%) |
| Tertiary form | — | Dissolved in plasma (7%) |
| Curve shape | Sigmoid (cooperative) | More linear |
| Key effect | Bohr effect (right shift) | Haldane + Chloride shift |
Alveolar Anatomy Image
Source: Respiratory system — Wikimedia Commons
Breathing Muscles Summary
| Process | Muscles | Type |
|---|---|---|
| Quiet inspiration | Diaphragm + External intercostals | ACTIVE |
| Quiet expiration | None (elastic recoil) | PASSIVE |
| Forced expiration | Internal intercostals + Abdominals | ACTIVE |