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The Basic subset of the UBERON integrated, cross-species anatomy ontology is downloaded weekly from For more information about this ontology see the "About" page on the UBERON website at

Term:primitive knot
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Accession:UBERON:0003062 term browser browse the term
Definition: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].
Synonyms:exact_synonym: Hensen node;   Hensen's node;   Spemann Mangold organizer;   Spemann's organizer;   embryo organizer;   embryonic organizer;   embryonic shield;   organizer;   primitive node;   shield
 broad_synonym: node
 related_synonym: DMZ;   Henson's node;   dorsal marginal zone;   nodus primitivus
 alt_id: UBERON:0004018
 xref: AAO:0000346;   BILA:0000053;   BTO:0003395;   EHDAA2:0001272;   EHDAA:549;   EMAPA:16075;   FMA:293116;   GAID:1312;   MESH:D020897;   NCIT:C34266;   SCTID:361464001;   TAO:0000071;   UMLS:C1283999;   VHOG:0000598;   Wikipedia:Regional_specification#Dorsal.2Fventral_axis_.26_organizer;   XAO:0000072;   ZFA:0000071

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Term paths to the root
Path 1
Term Annotations click to browse term
  UBERON ontology 0
    anatomical entity 0
      material anatomical entity 0
        developing anatomical structure 0
          embryonic structure 0
            primitive knot 0
              axial hypoblast + 0
Path 2
Term Annotations click to browse term
  UBERON ontology 0
    anatomical entity 0
      material anatomical entity 0
        anatomical structure 0
          multicellular anatomical structure 0
            multicellular organism 0
              tissue 0
                epithelium 0
                  unilaminar epithelium 0
                    simple columnar epithelium 0
                      primitive streak 0
                        primitive knot 0
                          axial hypoblast + 0
paths to the root