The neural crest is a population of migratory and pluripotent cells that are formed during the development of vertebrates. This population originates at the edges of the neural tube and the epidermis of the embryo. These cells migrate, colonizing a large part of the embryo shortly after the end of neurulation. The neural crest is sometimes referred to as the fourth germ layer because of its great importance in development.
Neural crest cells are very important and their ultimate goal will depend on where they migrate:
- Neurons of sensory, spinal, and cranial nerve ganglia V, VII, IX, and X.
- Neurons of the ANS ganglia.
- Nerves (except somatic and preganglionic autonomous motor fibers).
- Schwann cells and satellite cells of the sensory and autonomic ganglia.
- The pia mater and arachnoid of the telencephalon, the diencephalon, and the upper half of the midbrain.
- Melanocytes.
- The odontoblasts.
- Connective tissue and craniofacial bones.
- Chromaffin cells of the adrenal medulla.
- Prafollicular cells and thyroid tissue.
- Connective tissue of the thymus and parathyroid.
- Aortic pulmonary septum and semilunar valves of the heart.
- Connective tissue of the salivary glands.
- Ciliary muscle.
- Anterior epithelium and corneal proper substance.
- Part of the connective tissue of the lacrimal glands.
For the correct migration and formation of the neural crest derivatives, some genetic factors are needed, such as BMP and Wnt6, which, when found at high levels in the presumed epidermis, start the process.
According to its arrangement throughout the embryo, the neural crest can be divided into four main domains that can overlap:
- Cranial or cephalic neural crest: It differs in cartilage, bone, cranial neurons, glia, and connective tissue of the face.
- Neural trunk of the trunk: cells that migrate little are responsible for forming ganglia that form sensory neurons, while cells that migrate ventrally form mainly sympathetic ganglia and the adrenal medulla. The cells in this domain are then transformed into pigment- synthesizing melanocytes.
- Vague and sacral neural crest: generates parasympathetic ganglia of the intestine.
- Cardiac neural crest: These cells can generate melanocytes, neurons, cartilage, and connective tissue. It originates all the connective-muscular tissue of the arterial walls as they are generated from the heart.
