mesocardia mes·o·car·di·a (měz'ə-kär'dē-ə, měs'-)
n.
An atypical central position of the heart in the chest, as in the embryo.
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.