The papillary muscles of the heart are conical projections into the respective chamber of myocardium covered by endocardium. Their bases rest on the ventricular or septal walls. At their apices are a number of chordae tendineae - fine fibrous cords of collagen. Usually, the latter insert into the free edges and ventricular surfaces of the respective valve.
Functionally, the papillary muscles are part of the respective valve complex. They prevent the cusps of a valve from being everted when the ventricle contracts.