•  Primary components:
  • Sinoatrial node (SA)
  • Atrioventricular node (AV)
  • Bundle of His
  • Right and left bundle branches
  • Purkinje system
• Pacemaker nodal cells 
  • P cells or round cells
  • Transitional or T cells

unknown original source; if this image is in violation of copyright, please inform us.  

• SA nodal location: in the right atrial wall at the junction of the right atrium with the superior vena cava (SVC)

above image courtesy of Marquette Electronics

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• Connections between the SA  & AV nodes: internodal conduction system composed of:

  1. anterior (Bachman's bundle)

  2. middle bundle

  3. posterior internodal systems

• Left atrial activation: Bachman's bundle

• AV nodal  location: in the right atrial floor {near the coronary sinus ostium}

image from An Atlas and Practical Guide to Histology, by Dr. Kenneth Chan with technical assistance from Dr. Simon Cool & Mr. Duncan McCardle. The University of Queensland, Department of Anatomical Sciences © 1998   

• AV nodal anatomy: 3 regions

  •  A-N transitional zone {cells smaller than normal atrial cells}

  •  N region {consisting of  round/P cells (similar to SA nodal cells)}

  •  N-H region {transitional area, near the bundle of His}

• Bundle of His pathway:

  1. Traverses the superior edge of the interventricular septum to the septal muscular portion apex

  2. Divides into right and left bundle branches

  3. Branches extend towards the subendocardium along ventricular surfaces

• Right Bundle of His pathway

  • Emerges in the right ventricular endocardium (near the base of the anterior papillary muscle)

    • one branch passes through the moderator band

    • the second branch traverses over the right ventricular endocardial surface

• Left Bundle of His pathway

  • Left bundle subdivision:

    • anterior & posterior fascicles -- division shortly after left bundle branch origin {medial fascicle come originating from the left bundle, just after the anterior fascicle}

      • medial fascicle: activates septal myocardium

• Right & left bundle branch Fascicle terminations:

  • Subdividing, forming the Purkinje system

    • Left bundle branch fascicle:

      • initial endocardium contact: interventricular septum, below the aortic valve

    • Right bundle-branch fascicle:

      • initial  anatomical contact: ventricular subendocardium (near anterior papillary muscle base)

Summary

unknown original source; if this image is in violation of copyright, please inform us.  

Poul-Erik Paulev, M.D., D.Sci Textbook in Medical Physiology And Pathophysiology Essentials and clinical problems Copenhagen Medical Publishers 1999 - 2000 All rights reserved. used with permission

  

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