The tricuspid valve is more differentiated during evolutionary development than
the mitral valve. In birds it is a muscular structure joined directly to the papillary
muscles, although the mitral valve of birds resembles that of mammals. There
have been well-known studies describing the evolutionary line of connection of
the tricuspid valve with the papillary muscles.
The present study was performed on a group of 107 formalin-fixed adult human
hearts. The valves and papillary muscles were classified according to a scheme for
human hearts drawn up earlier. The types of connection between leaflets of the
tricuspid valve and the papillary muscles were classified according to a scheme drawn
up earlier for vertebrates. We observed 3 types of connection between leaflets of
the tricuspid valve and the papillary muscles in the group studied. The muscular and
membranous connections were not linked with any one type of tricuspid valve.
Atypical forms of distribution of the tendinous chords of the right ventricle were
observed. It was found that valves with a higher number of leaflets were (with the
exception of type 0) provided with a smaller number of tendinous chords.
Atavistic features and atypical forms of distribution of the tendinous chords are
present in a small percentage of samples of the human right valvular apparatus