part of part of in taxon develops from develops from contributes to morphology of immediate transformation of Vertebrata <vertebrates> embryo embryonic structure germ ring primitive knot EHDAA2:0001272 node A signaling center that directs the development of the whole embryo or of part of the embryo.[AAO] Organizer for gastrulation in vertebrates. The primitive knot starts as a regional knot of cells that forms on the blastodisc immediately anterior to where the outer layer of cells will begin to migrate inwards - an area known as the primitive streak. Posterior to the node is the primitive pit, where the cells of the epiblast (the upper layer of embryonic cells) initially begin to invaginate. This invagination expands posteriorly into the primitive groove as the cells layers continue to move into the space between the embryonic cells and the yolk. This differentiates the embryo into the germ layers - endoderm, mesoderm, and ectoderm. The primitive knot migrates posteriorly as gastrulation proceeds, eventually being absorbed into the tail bud.[WP]. the regional thickening of cells at the rostral tip of the vertebrate primitive streak through which gastrulating cells migrate anteriorally to form tissues in the future head and neck; this region organizes the formation of the three embryonic layers and establishes the longitudinal axis and the polarity of the embryo[MP]. Spemann Mangold organizer embryonic organizer primitive node This class groups together possibly disparate structures, following homology class in vHOG; early development terms need review Hensen node Wikipedia:Regional_specification#Dorsal.2Fventral_axis_.26_organizer Embryonic structure that is a local accumulation of cells along the germ ring. The shield marks the dorsal side of the embryo[ZFIN:ZDB-PUB-961014-576]. UMLS:C1283999 The organizer is a central feature of vertebrate embryogenesis. It was first characterized in functional terms in amphibians by Spemann and Mangold (1924), and homologous tissues have since been identified in representatives of most other vertebrate classes, including mammals (the node), birds (Henson's node) and teleost fish (the embryonic shield).[well established][VHOG] embryonic shield Hensen's node FMA:293116 EMAPA:16075 XAO:0000072 DMZ TAO:0000071 BTO:0003395 Henson's node NCIT:C34266 UBERON:0003062 ZFA:0000071 AAO:0000346 Spemann's organizer MESH:D020897 SCTID:361464001 EHDAA:549 GAID:1312 BILA:0000053 nodus primitivus organizer UBERON:0004018 dorsal marginal zone embryo organizer shield VHOG:0000598 primitive streak presumptive shield protuberance