Heart Sounds and Cardiovascular Cycle
Introduction
- Heart Sounds: "Lub-dub" is the classic sound heard with each heartbeat.
- Source: Sounds originate from closing of heart valves during the cardiac cycle.
Blood Flow Through the Heart
- Chambers: Blood moves through four chambers (right/left atrium, right/left ventricle).
- Pathway:
- Veins → Right Atrium → Right Ventricle → Pulmonary Arteries → Lungs → Pulmonary Veins → Left Atrium → Left Ventricle → Aorta.
Heart Valves
- Function: Allow blood to pass through when open, hold blood within a chamber when closed.
- Types:
- Atrioventricular Valves:
- Mitral Valve: Left side.
- Tricuspid Valve: Right side.
- Semilunar Valves:
- Pulmonary Valve: Right side.
- Aortic Valve: Left side.
Listening to Heart Sounds
- Aortic Valve: Right second intercostal space, next to sternum.
- Pulmonary Valve: Left second intercostal space, next to sternum.
- Tricuspid Valve: Between the fourth and fifth rib, next to sternum.
- Mitral Valve: Fifth intercostal space near midclavicular line.
Cardiac Cycle Phases
- Diastole:
- Ventricles relax and fill with blood.
- Atrioventricular valves open.
- Atrial contraction gives blood an extra push.
- Systole:
- Ventricles contract and push blood out.
- Semilunar valves open.
Heart Sounds Explained
- First Heart Sound (S1):
- "Lub": Closing of tricuspid and mitral valves.
- Best heard in tricuspid and mitral valve areas.
- Second Heart Sound (S2):
- "Dub": Closing of aortic and pulmonary valves.
- Best heard in aortic and pulmonary valve areas.
- Physiologic Splitting of S2: During inspiration, S2 splits due to delayed pulmonary valve closure.
Summary
- Heart Sounds:
- Two normal sounds: S1 and S2.
- S1: Atrioventricular valves closing at systole's start.
- S2: Aortic and pulmonary valves closing at diastole's start.
These notes summarize key aspects of heart sounds, valve functions, and the cardiac cycle, providing an overview of how heart sounds are produced and where they can be listened to on the chest.