Neural crest

The neural crest is a structure formed during the third week of embryonic development during the process of neurulation, i.e. the formation of the neural tube. Neural crest cells migrate from their site of origin and underlie many diverse tissues and cell types throughout the embryo. For this reason, the neural crest is considered by some embryologists to be the fourth foetal membrane.

Formation of neural crest
During the third week, neural plate formation is first induced by increased fibroblast growth factor (FGF) signaling and inhibition of bone morphogenetic protein 4 (BMP4). It soon begins to increase in length and its lateral edges thicken into neural mounds, between which a sunken neural furrow remains. The neural crest is located at the very edge of the neural crest.



Further fate of neural crest cells
Cells located at the site of the neural crest undergo epithelo-mesenchymal transformation during neural tube closure, thereby escaping the neural tube and migrating to a number of locations throughout the body of the embryo where they will later differentiate into cells of various tissues, hold various functions. The escape time from the neural tube as well as the use of these cells varies slightly depending on the part of the body where they are located.

Neural strip in trunk area
In the trunk region, the neural crests first fuse to close the neural tube, and only then do the neural crest cells leave them. Subsequently, a double fate awaits them. On the one hand, they migrate dorsally through the future dermis and penetrate openings in the basal lamina into the ectoderm, where they differentiate into melanocytes of the skin and hair follicles, on the other hand, ventrally to transform into neurons and glia of the spinal and autonomic ganglia and enteric nervous system, in Schwann cells and in adrenal medulla cells.



Neural strip in head and neck area
The neural crest cells in this region leave the neural crests before they join. Some of their future fates are similar to those of the trunk, namely transformation into melanocytes and transformation into the majority of neurons and glial cells of the cranial nerve ganglia (some of the cells also originate from the epibranchial placodes). Other formations are already typical for the head and neck area. Primarily, the cells of the neural crest give rise to connective tissues, as well as the dermis in this area. Furthermore, some of the cells grow into the ultimobranchial bodies and, after their migration caudally, transform into parafollicular cells (C-cells) of the thyroid gland. Another typical and important task of neural crest cells from the hindbrain is their migration to the truncus arteriosus and its septation, i.e. division into the aorta and truncus pulmonalis.

Summary of the main derivatives of the neural strip

 * ligaments, cartilages and bones of the face and skull
 * the dermis of the face and neck
 * smooth muscle cells in the wall of blood vessels of the face and end brain
 * sensitive and parasympathetic ganglia cranial nerves
 * Meninges of the hindbrain
 * parafollicular thyroid cells
 * septum in truncus arteriosus
 * odontoblasts
 * spinal ganglia
 * ganglia of the autonomic nervous system
 * cells of the enteric nervous system
 * adrenal medulla
 * melanocytes