The cardiac skeleton


  • Fibrous rings surround the atrioventricular canals and the origins of the aorta and pulmonary trunk.
  • Membranous inter-ventricular septum


  • Attachment to the valves
  • Insertion for the cardiac muscle fibres.

The conducting system of the heart  


  • Consists of specialized cardiac muscle fibres

  • Initiate the normal heart beat

  • coordinate the contractions of the heart chambers.

  • Gives the heart its automatic rhythmic beat.

  • It consists of the following components:

    a) Sino Atrial Node : In the wall of right atrium: superior end of crista terminalis to the right of superior vena cava opening

    b) Atrio ventricular node: Postero-inferior part of intra-atrial septum, superior to opening of coronary sinus

    c) Atrio ventricular bundle of HIS : Runs anteriorly to membranous part of inter ventricular septum, lies inferior to septal cusp of tricuspid valve

    d) Right and Left bundle branches: Straddle the muscular parts of inter ventricular septum

    e) Purkinje fibres




Functioning of the impulse conducting system

  • The SA node initiates the impulse, which is rapidly conducted to the cardiac muscle fibres of the atria, causing them to contract.

  • The impulse enters the AV node.

  • It is then transmitted through the AV bundle to

  • Its branches to the papillary muscles, then throughout the walls of the ventricles.

Although the heart has its own intrinsic rythmicity , this is subject to the influence of the autonomic nervous system.


Home | Project Anatomy | Gross Anatomy | Topic Index | Chapter 29

Chapter 29: The Middle Mediastinum, Heart and Pericardium and the Superior Mediastinum