The universal church is: the total company of the redeemed; all true believers of all ages in all places (including Old Testament saints); those whose names are written in the Lamb's Book of Life.
Jesus, and Jesus alone, is the Head of the church. He founded it; it belongs to him; it is answerable to him alone and not to any man (popes, etc) or men (synods, etc). A multi-headed body is a monster.