endochorion FBbt:00000040 inner endochorion One of the outer layers that envelops the oocyte and forms part of the eggshell. It surrounds the inner chorionic layer and is in turn enveloped by the exochorion. The endochorion is composed of a thin floor (or inner endochorion), and a continuous domed roof (or outer endochorion). The floor and roof are connected by vertical pillars. The outer surface of the roof shows protrusions organized in a regular roof network. fly_anatomy.ontology outer endochorion chorionic layer