Question

Describe how the time and place of gastrulation of cells result in different mesodermal tissues having the ability to pattern the ectoderm in vertebrates, and what molecules those mesodermal tissues release.

Answer 1

Gastrulation is a morphogenetic process that results in the formation of mesoderm and the generation of a three germlayered embryo composed of ectoderm. Gastrulation is not complete until three layers of cells are present. Ectoderm, mesoderm and endoderm are called the embryonic germ layers. The inner cell mass now has flattened into the embryonic disc composed of two layers of cells, ectoderm above and ectoderm below. Once the embryonic disc elongates to form primitive streak, found in vertebrates, the third germ layer mesoderm, forms by navigation of cells along streak. Signal molecules normally released only by mesoderm.