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 Henson's node 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]. NCIT:C34266 UBERON:0003062 ZFA:0000071 AAO:0000346 embryonic organizer primitive node MESH:D020897 SCTID:361464001 EHDAA:549 GAID:1312 Wikipedia:Regional_specification#Dorsal.2Fventral_axis_.26_organizer BILA:0000053 organizer UBERON:0004018 embryonic shield FMA:293116 EMAPA:16075 XAO:0000072 DMZ dorsal marginal zone embryo organizer shield TAO:0000071 BTO:0003395 VHOG:0000598 primitive streak presumptive shield protuberance