WThe ectoderm is the most exterior of the three primary germ layers formed in the very early embryo. The other two layers are the mesoderm, and endoderm. It emerges and originates from the outer layer of germ cells. The word ectoderm comes from the Greek ektos meaning "outside", and derma meaning "skin."
WIn Xenopus laevis, the specification of the three germ layers occurs at the blastula stage. Great efforts have been made to determine the factors that specify the endoderm and mesoderm. On the other hand, only a few examples of genes that are required for ectoderm specification have been described in the last decade. The first molecule identified to be required for the specification of ectoderm was the ubiquitin ligase Ectodermin ; later, it was found that the deubiquitinating enzyme, FAM/USP9x, is able to overcome the effects of ubiquitination made by Ectodermin in Smad4. Two transcription factors have been proposed to control gene expression of ectodermal specific genes: POU91/Oct3/4 and FoxIe1/Xema. A new factor specific for the ectoderm, XFDL156, has shown to be essential for suppression of mesoderm differentiation from pluripotent cells.
WEctodermal dysplasia (ED) is a group of genetic syndromes all deriving from abnormalities of the ectodermal structures. More than 150 different syndromes have been identified.
WHypohidrotic ectodermal dysplasia is one of about 150 types of ectodermal dysplasia in humans. Before birth, these disorders result in the abnormal development of structures including the skin, hair, nails, teeth, and sweat glands.
WNeural crest cells are a temporary group of cells unique to vertebrates that arise from the embryonic ectoderm germ layer, and in turn give rise to a diverse cell lineage—including melanocytes, craniofacial cartilage and bone, smooth muscle, peripheral and enteric neurons and glia.
WIn the developing chordate, the neural tube is the embryonic precursor to the central nervous system, which is made up of the brain and spinal cord. The neural groove gradually deepens as the neural folds become elevated, and ultimately the folds meet and coalesce in the middle line and convert the groove into the closed neural tube. In humans, neural tube closure usually occurs by the fourth week of pregnancy. The ectodermal wall of the tube forms the rudiment of the nervous system. The centre of the tube is the neural canal.
WNeuroectoderm consists of cells derived from ectoderm. Formation of the neuroectoderm is first step in the development of the nervous system. The neuroectoderm receives bone morphogenetic protein-inhibiting signals from proteins such as noggin, which leads to the development of the nervous system from this tissue. Histologically, these cells are classified as pseudostratified columnar cells.
WThe surface ectoderm forms the following structures:Skin Epithelium of the mouth and nasal cavity and glands of the mouth and nasal cavity Tooth enamel (as a side note, dentin and dental pulp are formed from ectomesenchyme which is derived from ectoderm Epithelium of anterior pituitary Lens, cornea, lacrimal gland, tarsal glands and the conjunctiva of the eye Apical ectodermal ridge inducing development of the limb buds of the embryo. Sensory receptors in epidermis