The cardiac valves develop from the endocardial cushions of the fetus. Some 
congenital anomalies such as the 21-trisomy syndrome (Down syndrome) show poorly 
differentiated immature valves similar to those under development. The normally 
mature valves have four layers of the connective tissue, i.e., proximalis, 
spongiosa, fibrosa and distalis. Gargoylism promotes abnormal thickening of 
collagen fibers in the fibrosa via acid-mucopolysaccharide (aMPS) 
overproduction, but Marfan syndrome weakens the valves in spite of increased 
aMPS. The reversed conditions could be caused by the difference of increased 
aMPS; i.e., dermatan sulfate B or heparitin sulfate in gargoylism, on the 
contrary, dermatan sulfate A and C or hyaluronic acid in Marfan syndrome. 
Hemodynamic changes in the valves consist of diffuse hypertrophy of the 
proximalis and fibrosa in high flow cases and focal thickening of the proximalis 
at the line of closure and of the spongiosa at the anatomical edge in high 
pressure cases. Aging of the valves simulates partly the hemodynamic changes but 
degeneration of collagen fibers in the fibrosa after consumption of the 
spongiosa is more prominent than the latter. So-called myxomatous degeneration 
in the mitral valve prolapse cases seems reactive hypertrophy of the spongiosa 
replacing the interrupted fibrosa. Spontaneous chordal rupture is partly related 
to myxomatous change, but that in the elderly cases shows only simple disruption 
of collagen fibers with loss of the spongiosa tissue. Calcification of the 
valvular rings and bodies often observed in the elderly cases with parallelism 
to degeneration of the connective tissue produces mitral regurgitation, aortic 
stenosis or both, showing a preponderance of females.(ABSTRACT TRUNCATED AT 250 
WORDS)