Structural basis for cardiac function.

ARMOUR, J. A., AND W. C. RANDALL. Structural basis for cardiac function. Am. J. Physiol. 218(6): 1517-1523. 1970.-In nine species of,mammals, anatomic evaluation of fresh specimens demonstrated that the ventricles of the heart are grossly structured as a continuum of muscle strands. These strands originate and insert into a basal fibrous skeleton consisting of four interconnected, triangular accumulations of fibrous tissue surrounding the aortic valve. They undergo a slow right-angular directional change as they course from the epicardium to the endocardium. Vertically directed strands of the endocardium and the papillary muscles originate from these innermost strands, the latter playing an important role in the formation of inflow and outflow tracts within the left ventricle. Right ventricular sinus musculature is anatomically similar to that of the left, but the conus strands run more nearly parallel to form a potentially separate cylindrical chamber at the base of the pulmonary artery. Incisions following the direction of the muscle strands do not grossly alter cardiac function, whereas cutting across the strands seriously interferes with normal activity. It is concluded that anatomic considerations are of paramount importance in determining the specific effectiveness of each individual portion of the ventricles in performing its particular function.