0 the cells in the embryo of a human or animal that develop into skin, hair, and the nervous system --
1 the cells in the embryo (= growing organism before it is born) of a human or animal that develop into skin, hair, and the nervous system --
Each structure originates form different germinative layers or tissues: the ectoderm, endoderm and mesenchyme.
Embryos have three layers: endoderm, mesoderm and ectoderm.
This leads to the specification of non-neural ectoderm and later in the blastula stage to anmioserosa.
It is not a teratoma, however, which is a neoplasm comprising all three germ cell layers (ectoderm, endoderm, mesoderm).
At this point, there are two layers of cells - the ectoderm (outermost) and the endoderm (innermost) layers.
Presumptive neural crest cells initially lie in the neural folds at the juncture between the neural and non-neural ectoderm and then within the dorsal neural tube after its closure.
During this complex developmental process, the outer embryonic ectoderm and its underlying mesoderm give rise to the epidermal and dermal components, which essentially build up the hair follicle unit.
During the next few days the outer surface of the embryo (or ectoderm) folds in upon itself to form the neural tube.
