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The neural crest is a group of cells created very early into the embryonic development of all vertebrates. It is created in a process called neurulation, which also begins the formation of the defining characteristic of vertebrates — a brain and spinal cord protected by skull and backbone. The cells of the neural crest proceed to develop into other features unique to vertebrates, such as the shape and structures of the head.
Human embryology is the study of how a human being develops from a single fertilized egg cell to a fully functioning baby within a woman’s womb. Just twenty days into development, the embryo is still a relatively undifferentiated hollow ball, its wall just three cells thick. During neurulation, an area of its outermost layer of cells, called the ectoderm, pinches together. When the edges meet and fuse, the extruded result is a hollow tubular structure called the neural tube. The neural tube eventually develops into the brain and spinal cord.
When the neural tube is completed, the group of cells responsible for the pinching movement of neurulation slough off, no longer needed. These are the neural crest cells. They become free to move elsewhere within the young embryo. The neurulation process has produced the first distinctly differentiated structure of the human embryo. It has also produced mobile cells which migrate to many locations to begin developing into other body structures.
By tagging neural crest cells with dyes, laboratory studies with other vertebrates have identified where they go and what they become. Some develop into heart tissue. A group of neural crest becomes the nervous system the brain employs to control the internal organs of digestion. Other cells become specialized to produce melanin, the pigment that colors skin, hair and eyes. Many cells don’t migrate very far and begin transforming themselves into the many bones of the head and their connective tissues.
There is increasing knowledge of what the neural crest does at such an early stage of development, when the embryo is still mostly a formless ball. Scientists are busy studying the question of how they do it. Of specific interest is how a freely moving cell knows where to go. Once there, of additional interest is how it determines what type of very specialized cell into which it must developmentally evolve. Most research focuses on the two likely factors of genetically encoded directions within the cells and chemical communication with other cells.