Understanding Heart Sounds: "Lub-Dub"

Introduction

• The heart makes distinct sounds: "Lub" and "Dub".
• These sounds are written as "L-U-B-D-U-B" and they repeat continuously.
• The sounds are associated with the closing of heart valves.

Heart Anatomy and Blood Flow

• Heart Chambers:

  • Blood enters the right atrium, moves to the right ventricle, goes to the lungs, returns to the left atrium, and then to the left ventricle.

• Valves of the Heart:

  • Tricuspid Valve (T): Between right atrium and right ventricle.
  • Pulmonary Valve (P)
  • Mitral Valve: Between left atrium and left ventricle.
  • Aortic Valve

• Blood Flow Mechanics:

  • Blood flows into ventricles when tricuspid and mitral valves open.
  • Incorrect flow (black arrows) is prevented by valves closing.
  • Correct flow (white arrows) occurs when pulmonary and aortic valves are open and blood is ejected into arteries.

Heart Sound Mechanics

• Lub (S1):

  • Occurs when the tricuspid and mitral valves snap shut.
  • Known as the first heart sound (S1).

• Dub (S2):

  • Occurs when the pulmonary and aortic valves snap shut.
  • Known as the second heart sound (S2).

Cardiac Cycle Phases

• Systole (between Lub and Dub):

  • Blood is ejected to the body as the pulmonary and aortic valves open.

• Diastole (between Dub and next Lub):

  • Blood refills from the atria to the ventricles as the tricuspid and mitral valves open.

Listening to Heart Sounds

• S1 (Lub) indicates the beginning of systole.
• S2 (Dub) indicates the end of systole and beginning of diastole.
• Time between S1 and S2: Systole
• Time between S2 and next S1: Diastole

Summary

• The cycle of heart sounds and valve operations are crucial for understanding the flow of blood through the heart.
• These sounds reflect the coordinated opening and closing of heart valves, essential for effective cardiac function.