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]. [ MP:0004066 ]

This is just here as a test because I lose it

Term information

database cross reference

uberon_slim, pheno_slim, early_development

taxonomic disambiguation
Spemann Mangold organizer [ ZFA:0000071 ]

taxonomic disambiguation
Spemann's organizer [ ZFA:0000071 ]

editor note

This class groups together possibly disparate structures, following homology class in vHOG; early development terms need review

external definition

A signaling center that directs the development of the whole embryo or of part of the embryo.[AAO]

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].

has alternative id


has exact synonym

primitive node

Hensen's node


embryonic shield


Spemann's organizer

embryonic organizer

embryo organizer

Hensen node

Spemann Mangold organizer

has related synonym


Henson's node

dorsal marginal zone

nodus primitivus

homology notes

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]