GROSS MORPHOLOGY AND ARTERIAL SUPPLY OF THE PAPILLARY MUSCLES OF THE LEFT VENTRICLE IN RABBITS

1. The gross morphology and arterial supply of the papillary muscles of the left ventricle were studied in 160 rabbits'hearts. Radiopaque medium, latex or Chinese ink were injected into coronary arteris. After injection, arteriography or dissection of some hearts were taken and serial celloidin sections of the papillary muscles of other hearts were made. The length and width of the papillary muscles, the diameters and the density of the vessels were measured.2. The papillary muscles could be divided into three patterns, depending on the extent of their attachment to the ventricular wall and the relative length of their free part protruding into the ventricular cavity. The three patterns are: (1) the tethered type (38%), (2) the fingerlike type (10%), (3) the intermediate type (52%).3. The anterolateral papillary muscle received branches mainly from the anterior branches of the left ventricular artery. The posteromedial papillary muscle mainly received branches from the posterior branches of the left ventricular artery.4. The arrangement of the arterial vasculature of the papillary muscles seemed to be related to the different patterns of the papillary muscles. The finger-like type received a krge centralartery which coursed through the entire papillary muscle to its apex (70%). The tethered type had a segmental supply of 3-6 long penetrating intramyocardial vessels (89.47%). The intermediate type had a combination of both types of the vascular arrangement (100%).