part of develops from amnioserosa dorsal closure embryo apoptotic amnioserosa fly_anatomy.ontology FBbt:00005556 Amnioserosa following dorsal closure (Reed et al., 2004). It initially invaginates to form a tube with its perimeter cells aligning on the dorsal side of the tube, beneath the dorsal midline of the embryo (Reed et al., 2004). Individual cells dissociate from the tube and are engulfed by hemocytes, dying by anoikis (Reed et al., 2004). extraembryonic structure dorsal ectoderm derivative