Circulation and Heart Valves

End of the Heart - Atrioventricular Valves

  • Atrioventricular (AV) Valves: There are two types: the tricuspid valve (right heart) and the bicuspid (mitral) valve (left heart).

    • Function:
    • Allow blood flow from the atria to the ventricles when pressure builds up.
    • Prevent backflow of blood into the atria.
    • Mechanism of Action:
    • Valves open as the atria fill with blood, creating pressure.
    • Valves close due to pressure from the ventricles and are held in place by chordae tendineae and papillary muscles.

  • Chorda Tendineae and Papillary Muscles:

    • Chordae tendineae: Tendon-like structures connecting the valves to the ventricular walls.
    • Papillary muscles: Muscles that contract to prevent the AV valves from flipping back into the atria, ensuring proper blood flow direction.
    • Misconception: They do NOT actively open or close the valves; they prevent backflow.

Semilunar Valves

  • Types: Pulmonary semilunar valve (exiting right ventricle) and aortic semilunar valve (exiting left ventricle).
    • Function: Similar to AV valves but located at the exits of the ventricles. They allow blood to exit the ventricles to the pulmonary artery and aorta respectively and prevent backflow into the ventricles.
  • Mechanism of Action:
    • Open when ventricles contract and close when pressure decreases.

Blood Flow through Heart

  1. Deoxygenated Blood enters via:
    • Superior vena cava
    • Inferior vena cava
    • Coronary sinus
  2. Blood moves to the right atrium.
  3. Flows through the tricuspid valve to the right ventricle.
  4. From the right ventricle, it goes through the pulmonary semilunar valve into the pulmonary trunk.
  5. Then into pulmonary arteries to the lungs for oxygenation.
  6. Oxygenated blood returns via pulmonary veins to the left atrium.
  7. Moves through the bicuspid (mitral) valve into the left ventricle.
  8. Finally, it exits through the aortic semilunar valve into the aorta, delivering oxygenated blood to the body.

Coronary Circulation

  • Coronary arteries supply blood to the heart itself: Right and Left coronary arteries.
  • Coronary veins (Great cardiac vein, Middle cardiac vein, Small cardiac vein) drain deoxygenated blood from the heart wall into the coronary sinus, leading to the right atrium.

Heart Sounds and Murmurs

  • Heart Sounds: Sound produced by the closure of the valves during the cardiac cycle. Not directly the sound of the valves slamming shut but vibrations in the blood.
  • Murmurs: Abnormal sounds that indicate problems with the valves (e.g., if the AV valves do not close properly, leading to backflow).

Study Tips

  • Quiz yourself on blood flow using diagrams of the heart.
  • Use analogies for the heart valves (e.g., umbrella analogy for chordae tendineae and papillary muscle functions).
  • Ensure a clear understanding of systemic and pulmonary circulation pathways.
  • Be familiar with the anatomy and function of both artery and vein from lab experiences.

Anatomy Recap

  • Semilunar Valves: Have three cusps and open upwards during ventricular contraction.
  • Auricles: Fleshy extensions for increased filling capacity of atria (linked to how the blood fills).
  • Septum: Interventricular (separates ventricles) and interatrial (separates atria).

Common Misconceptions

  • Valves do NOT open/close due to muscle contraction; they operate based on pressure changes.
  • Veins can carry oxygenated blood (exception being pulmonary veins).

Next Steps

  • Reinforce muscle structure understanding of the heart and valvular mechanisms.
  • Prepare for anatomical identification of all associated structures.
  • Familiarize with different types of blood vessels and the flow of blood throughout the body systematically.