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What is the function of pectinate muscles of heart ?

Posted Aug 28 2011 10:27am

Pectinate muscles are specialized Intracardiac  muscle

  • Pectinate muscles are located mainly in the right atrium  , more  in right atrial  appendage , sparse in left atrium
  • Has muscle fibers arranged in a  comb like fashion.
  • Has less mechanical activity, no significant contribution to atrial contractility.
  • Can stretch and improve the voluminous nature of right atrium
  • The pectinate muscle  folds act as RA volume reserve  during adverse loading conditions . It helps RA dilate with out much wall stress.
  • Rarely it can be a cell of origin for focal atrial tachycardia

Image Source : Greys anatomy

The concertina like effect of pectinate muscle .

The atrial infolding increases the surface area of atrial chamber at times of dilatation , like  the music instrument .So,  these macro  folds ( like intestinal villi )  help overcome the  constantly changing volume status of right atrium.Since the  variation  left atrial blood flow is  not that much ,  the pectinate muscles  are not well developed  in the left atrium.

The same rules would apply for  why  there is excess  trabeculations  in right  ventricle  than  left  ventricle .


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