Neural fold
![A strip of specialized cells called the notochord (A) induces the cells of the ectoderm directly above it to become the primitive nervous system (i.e., neuroepithelium). The neuroepithelium then folds over (B). As the tips of the folds fuse together, a hollow tube (the neural tube) forms (C)—the precursor of the brain and spinal cord. Meanwhile, the ectoderm and endoderm continue to curve around and fuse to create the body cavity, completing the transformation of the embryo from a flattened disk to a three–dimensional body. Cells originating from the fused tips of the neuroectoderm (neural crest cells) migrate to various locations throughout the embryo, where they will initiate the development of diverse body structures (D).[5]](/uploads/202501/26/Embryonic_Development_CNS5103.png)
The neural fold is a structure that arises during neurulation in the embryonic development of both birds and mammals among other organisms. This structure is associated with primary neurulation, meaning that it forms by the coming together of tissue layers, rather than a clustering, and subsequent hollowing out, of individual cells (known as secondary neurulation). In humans, the neural folds are responsible for the formation of the anterior end of the neural tube. The neural folds are derived from the neural plate, a preliminary structure consisting of elongated ectoderm cells. The folds give rise to neural crest cells, as well as bringing about the formation of the neural tube.