Cardiac fibrous skeleton

Last revised by Assoc Prof Craig Hacking on 25 Aug 2021

The fibrous skeleton of the heart is a complex set of collagenous rings that connect annuli of all four cardiac valves. Between the four annuli are two trigones (right and left) and the membranous portions of the interatrial, interventricular, and atrioventricular septa. The annuli of the two semilunar valves are attached in a manner that resemble a figure of 8, which lies obliquely, almost vertically oriented in the sagittal plane.

There are several vital functions of the skeleton:

  • anchors the bases of the cardiac valves
  • keeps the atrioventricular and semilunar orifices patent
  • anchors the myocardium of the walls of all four cardiac chambers
  • allows independent atrial and ventricular contraction by electrically insulating the atria above the fibrous skeleton from the ventricles below

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Cases and figures

  • Figure 1: cardiac fibrous skeleton (Gray's illustrations)
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