mesocardium
noun
me·so·car·di·um
| \ -ˈkärd-ē-əm
\
\
Medical Definition of mesocardium
1
: the transitory mesentery of the embryonic heart
2
: either of two tubular prolongations of the epicardium that enclose the aorta and pulmonary trunk and the venae cavae and pulmonary veins