Overview
This lecture explains the origins of the heart's "lub dub" sounds, details heart valve function, and connects heart sounds to cardiac cycle phases.
Heart Anatomy and Blood Flow
- The heart has four chambers: right atrium, right ventricle, left atrium, and left ventricle.
- Blood flows from the right atrium to the right ventricle, then to the lungs, returns to the left atrium, and moves to the left ventricle.
- Four main heart valves control blood flow: tricuspid, pulmonary, mitral, and aortic valves.
Heart Valve Function
- Tricuspid valve (T) separates right atrium and right ventricle; mitral valve separates left atrium and left ventricle.
- Pulmonary valve controls flow from right ventricle to lungs; aortic valve controls flow from left ventricle to body.
- Valves open to allow correct blood flow and close to prevent backflow.
Origin of Heart Sounds (Lub Dub)
- "Lub" (S1): Occurs when tricuspid and mitral valves snap shut, preventing backflow into atria.
- "Dub" (S2): Occurs when pulmonary and aortic valves snap shut, preventing backflow into ventricles.
- When one set of valves closes, the other set opens simultaneously.
Heart Sounds and Cardiac Cycle
- The period between "lub" (S1) and "dub" (S2) is called systole, when ventricles contract and blood moves to arteries.
- The period between "dub" (S2) and the next "lub" (S1) is called diastole, when ventricles relax and fill with blood from atria.
Key Terms & Definitions
- S1 (First heart sound) — "Lub" sound caused by closure of tricuspid and mitral valves.
- S2 (Second heart sound) — "Dub" sound caused by closure of pulmonary and aortic valves.
- Systole — Phase when ventricles contract and pump blood to lungs and body.
- Diastole — Phase when ventricles relax and fill with blood from atria.
- Backflow — Blood flowing in the wrong direction, prevented by valve closure.
Action Items / Next Steps
- Review diagrams of heart chambers and valves.
- Practice identifying S1 and S2 during heart auscultation exercises.