Gastrulation then continues along the ventroposterior blastopore lip and posterior streak region, from where cells contribute to ventral and posterior mesoderm. Cells involuting further laterally in the blastopore, or entering via Hensen’s node and the anterior primitive streak, contribute to gut, notochord and somites. Cell fate studies have revealed that also the overall temporal sequence in which groups of endomesodermal cells internalize along the frog blastopore and amniote primitive streak are surprisingly similar: the first cells that involute around the amphibian blastopore lip in the organizer region, and that immigrate through Hensen’s node, contribute to foregut endoderm and prechordal plate. This view is substantiated by the common expression of several genes, including goosecoid, Cnot, noggin, nodal, and the sharing of strong axis-inducing properties upon transplantation. Īll structures are as yet considered as homologous. In fish it is known as the embryonic shield.In amphibians, it is known as the Spemann-Mangold organizer, named after Hans Spemann and Hilde Mangold, who first identified the organizer in 1924.

In other amniotes it is known as the primitive node.In birds the organizer is known as Hensen's node, named after its discoverer Victor Hensen.

Fate of blastopore birds