The Four Heart Valves: Mitral, Aortic, Pulmonary, and Tricuspid
The heart has four valves, not three. They ensure unidirectional blood flow through the cardiac chambers.
The Four Valves
| Valve | Location | Leaflets/Cusps | Function |
|---|
| Tricuspid | Right atrium → Right ventricle | 3 (anterior, posterior, septal) | Prevents backflow into RA during RV systole |
| Pulmonary | Right ventricle → Pulmonary artery | 3 (semilunar) | Prevents backflow into RV during diastole |
| Mitral (Bicuspid) | Left atrium → Left ventricle | 2 (anterior, posterior) | Prevents backflow into LA during LV systole |
| Aortic | Left ventricle → Aorta | 3 (semilunar) | Prevents backflow into LV during diastole |
Key Points
- AV valves (tricuspid, mitral) are tethered by chordae tendineae and papillary muscles.
- Semilunar valves (pulmonary, aortic) are self-supporting.
- Valve disease: stenosis (narrowing) or regurgitation (leakage) — causes volume/pressure overload.
- Common pathology: Mitral regurgitation, aortic stenosis, tricuspid regurgitation (often functional), pulmonic stenosis (congenital).
Clinical Assessment
- Auscultation: Murmurs at specific areas (aortic: RUSB; pulmonary: LUSB; tricuspid: LLSB; mitral: apex).
- Echocardiography: Gold standard for structure, function, gradients, regurgitation severity.
Understanding the four valves is fundamental to cardiovascular physiology and pathology.
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