trilaminar embryonic disc trilaminar embryonic disc a trilaminar embryonic disc (or trilaminary blastoderm, or trilaminar germ disk) is an early stage in the development of triploblastic organisms, which include humans and many other animals. it is the next stage from the earlier bilaminar embryonic disc. trilaminar embryonic discdetailsidentifierslatinblastodiscus trilaminaristeembryonic disc_by_e6.0.1.1.4.0.1 e6.0.1.1.4.0.1 anatomical terminology it is an embryo which exists as three different germ layers – the ectoderm, the mesoderm and the endoderm. these layers are arranged on top of each other, giving rise to the name trilaminar, or "three-layered". the mesoderm is segmented further into the paraxial, intermediate and the lateral plate mesoderm. these three layers arise early in the third week (during gastrulation) from the epiblast (a portion of the mammalian inner cell mass).