Pulmonary Artery vs. Pulmonary Vein: Structural and Functional Comparison
The pulmonary circulation is unique: arteries carry deoxygenated blood, veins carry oxygenated blood.
Comparison
| Feature | Pulmonary Artery | Pulmonary Vein |
|---|---|---|
| Blood carried | Deoxygenated (mixed venous) | Oxygenated |
| Origin | Right ventricle | Pulmonary capillaries |
| Destination | Pulmonary capillaries | Left atrium |
| Pressure (mean) | 15 mmHg (low) | 8 mmHg (lower) |
| Wall thickness | Thin (less muscle/elastin) | Thinner |
| Diameter (main) | ~3 cm (trunk) | ~1.5 cm (each) |
| Valves | Pulmonary valve | None |
| O₂ saturation | ~75% | ~98% |
Key Physiological Points
- Low pressure, high compliance → accommodates entire cardiac output.
- Hypoxic pulmonary vasoconstriction (HPV) redirects flow to ventilated alveoli.
- Pulmonary hypertension: mean PAP >20 mmHg (RHC); remodels arteries (intimal hyperplasia, plexiform lesions).
Clinical Relevance
- PE obstructs pulmonary arteries → ↑ RV afterload → RV failure.
- Pulmonary venous hypertension (left heart failure) → ↑ capillary pressure → edema.
- Catheterization: PA catheter (Swan-Ganz) floats from RV → PA → wedge (reflects LA pressure).
Remember: "Artery = away from heart" holds; oxygenation is reversed in pulmonary circuit.
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