Neural crest

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Formation of the neural tube with the neural crest (green dots) from the neural plate .
Cell migration from the neural crest area
Cell types formed by the ectoderm

The formation of the neural crest is an intermediate step in the neurulation of an embryo and occurs only in the animal strain of the chordata , which also includes the vertebrates .

The neural crest is created on the back by an invagination of the ectoderm along a longitudinal axis . From this channel-like structure is formed by progressive neurulation , the neural tube , which between epidermis and notochord is located. The neural crest consists of bilateral (bilateral) rows of cells in the area of ​​the bulges of the embryonic neural tube, which join together. Cells of the neural crest then travel to remote locations in the developing embryo , where several of them structures.

In the course of the development of the organs , those organ structures or organs that arise from the ectoderm , endoderm and mesoderm are gradually perfected structurally through morphogenesis and cell differentiation . It is only in vertebrates that these ligaments of cells, which are called neural crest cells, tie off on both sides of the neural tube . They migrate, colonizing different regions of the embryo . The pigment cells of the skin ( melanocytes ), sensory cells of the skin, cartilage elements of the jaw , certain bones and muscles of the skull , parts of the teeth , the adrenal medulla and components of the peripheral nervous system as well as sensory and sympathetic ganglia develop from them . Melanocytes also migrate into the stria vascularis of the inner ear and the auditory nerves , as well as the iris of the eye and the optic nerves .

Studies of neural crest cells have shown that their development in vertebrate embryos depends on biochemical signals . Neural crest cells from chicken embryos that have migrated into the organ systems of the adrenal glands can develop into endocrine cells of the adrenal medulla if they are exposed to the influence of hormones in the adrenal cortex . However, if the same neural crest cells are exposed to the nerve growth factor NGF, they develop into neurons of the sympathetic nervous system . The Schwann cells and neurons for the innervation of the large intestine also arise from neural crest cells (see also vegetative nervous system ). If this innervation of the large intestine fails to occur due to an embryonic development disorder ( aganglionosis ), it can lead to a megacolon .

Individual evidence

  1. ^ Neil A. Campbell , Jane B. Reece : Biology. Spektrum-Verlag 2003, ISBN 3-8274-1352-4 , page 1208.
  2. Saskia K. Hogreve: Studies on hearing ability. Uni Giessen 2003, p. 11 and p. 25, online (PDF).
  3. ^ Neil A. Campbell , Jane B. Reece : Biology. Spektrum-Verlag 2003, ISBN 3-8274-1352-4 , p. 1163.