Main Entry: me·so·car·di·um Pronunciation: -'kärd-E-&m Function: noun 1: the transitory mesentery of theembryonic heart 2: either of two tubular prolongations of the epicardium that enclose the aorta and pulmonary trunk and the venae cavae and pulmonary veins
mesocardium mes·o·car·di·um (měz'ə-kär'dē-əm, měs'-) n.pl.mes·o·car·di·a (-dē-ə) Either of the two layers of the embryonic mesentery supporting the embryonic heart in the pericardial cavity.