Triploblastic is a condition of the ovum in which there are three primary germinal layers : the ectoderm, mesoderm, and endoderm. Additionally, the term may refer to any ovum in which the blastoderm splits into three layers. In higher and intermediate animals, all organisms arise from a triploblastic ovum.
Triploblastic organisms are organisms which evolve from such an ovum.
Unlike diploblastic animals, in which cells are proximate to the organism's environment, triploblastic animals have internal cells that are not adjacent to external food sources. Since all cells must be fed and waste removed, these tasks are handled by various organs and circulatory and digestive systems in any triploblastic animal.
Compare to diploblastic.