primitive node

synonym: primitive knot
https://doi.org/10.1351/goldbook.11129

Group of cells at the anterior end of the primitive streak, involved in secreting chemical signals that regulate differentiation of the germ layers during gastrulation.

Source:
PAC, 2016, 88, 713. (Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)) on page 796 [Terms] [Paper]