The<unk> , a transient component of the ectoderm, is located in between the<unk>  tube and the epidermis (or the free margins of the<unk>  folds) of an embryo during<unk>  tube formation.<unk>  cells quickly migrate during or shortly after<unk> ation, an embryological event marked by<unk>  tube closure.
It has been referred to as the fourth germ layer, due to its great importance. The<unk>  can give rise to neurons and glia of the peripheral nervous system (PNS); some skeletal elements, tendons and smooth muscle; chondrocytes, osteocytes, melanocytes, chromaffin cells, and supporting cells and hormone producing cells in certain organs.
Neural crest
Mesoderm
Notochord
Yolk sac
Odontoblast
Lung buds
Germ layer
Osteotome