ectoderm

(redirected from ectodermal)
Also found in: Dictionary, Thesaurus, Medical, Wikipedia.
Related to ectodermal: ectodermal dysplasia

ectoderm,

layer of cells that covers the surface of an animal embryo after the process of gastrulation has occurred. This outer layer, together with the endodermendoderm
, in biology, inner layer of tissue formed in the gastrula stage of the developing embryo. At the end of the blastula stage, cells of the embryo are arranged in the form of a hollow ball.
..... Click the link for more information.
, or inner layer, is present in all early embryos. In the development of animals of the phyla PoriferaPorifera
[Lat.,=pore bearer], animal phylum consisting of the organisms commonly called sponges. It is the only phylum of the animal subkingdom Parazoa and represents the least evolutionarily advanced group of the animal kingdom.
..... Click the link for more information.
, CtenophoraCtenophora
, a small phylum of exclusively marine, invertebrate animals, commonly known as comb jellies. Because they are so delicate that specimens are difficult to collect, little was known about them until the advent of blue-water scuba and submersible collecting.
..... Click the link for more information.
, and CnidariaCnidaria
or Coelenterata
, phylum of invertebrate animals comprising the sea anemones, corals, jellyfish, and hydroids. Cnidarians are radially symmetrical (see symmetry, biological).
..... Click the link for more information.
, these two primary layers give rise to all the tissues and organs of the animals, a process known as diploblastic development. In higher animals, such as those of the phyla EchinodermataEchinodermata
[Gr.,=spiny skin], phylum of exclusively marine bottom-dwelling invertebrates having external skeletons of calcareous plates just beneath the skin. The plates may be solidly fused together, as in sea urchins, loosely articulated to facilitate movement, as in sea
..... Click the link for more information.
 and ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
..... Click the link for more information.
, a third, middle layer, the mesodermmesoderm,
in biology, middle layer of tissue formed in the gastrula stage of the developing embryo. At the end of the blastula stage, cells of the embryo are arranged in the form of a hollow ball.
..... Click the link for more information.
, is formed between the ectoderm and endoderm during gastrulation, and the process is termed triploblastic development. In most embryos, differentiation of ectodermal tissue gives rise to epidermis and its specialized structures (scales, feathers, nails, and hair); some exocrine glands (sweat and sebaceous glands); some endocrine glands (the pineal body and the pituitary gland); the nervous system; and the organs of special sense (ear and eye). In animals of some phyla, such as the MolluscaMollusca
, taxonomic name for the one of the largest phyla of invertebrate animals (Arthropoda is the largest) comprising more than 50,000 living mollusk species and about 35,000 fossil species dating back to the Cambrian period.
..... Click the link for more information.
 and AnnelidaAnnelida
[Lat., anellus=a ring], phylum of soft-bodied, bilaterally symmetrical (see symmetry, biological), segmented animals, known as the segmented, or annelid, worms.
..... Click the link for more information.
, the fate of particular cells of the embryo is determined in the earliest stages of the fertilized egg and may even be fixed at or before fertilization.

Ectoderm

 

(1) The outermost germ layer; the external layer of the embryo of multicellular animals in the gastrular stage. From the ectoderm are formed the integuments, nervous system, sensory organs, anterior and posterior sections of the digestive tract, external gills, and ectomesenchyme. In the Deuterostomia, all the elements derived from the ectoderm are formed as a result of the action upon it of the chordomesoderm, the entoderm, and their derivatives.

(2) The external wall of the body of coelenterates. The ectoderm consists of a single layer of cells—epithelial, epithelio-muscular, interstitial, and sensory cells, as well as stinging capsules.

ectoderm

[′ek·tə‚dərm]
(embryology)
The outer germ layer of an animal embryo. Also known as epiblast.
(invertebrate zoology)
The outer layer of a diploblastic animal.
References in periodicals archive ?
The EVC syndrome, a rare genetic disorder, was first described by Richard Ellis and Simon van Creveld in 1940 and is characterized by short stature, polydactyly, ectodermal dysplasia, and congenital heart defects.
Conclusion: The study shows that sodium phenytoin exerts an inhibitory effect on the apical ectodermal ridges of developing limbs evident by the decreased number of mitoses in the AER of wing buds of experimental chick embryos making it a potential target site for limb teratogenicity associated with its maternal intake during pregnancy.
Early prosthetic treatment of patients with ectodermal dysplasia: A clinical report.
See: Ectodermal Dysplasias; Epilepsy; Incontinentia Pigmenti; Vitiligo
In recent years, Schalk van der Weide and Nordgarden reported observing other ectodermal symptoms in many individuals with oligodontia [34,35], implying an under-diagnosis of EDs.
Early prosthetic therapy for children with ectodermal dysplasia provides a unique opportunity for cooperative effort between the pedodontist and the prosthodontist, as pedodontists are better trained in the psychological management of children.
Most people with hypohidrotic ectodermal dysplasia have a reduced ability to sweat (hypohidrosis) because they have fewer sweat glands than normal or their sweat glands do not function properly.
Conclusion: The possibility of mature teratoma must be considered both grossly and microscopically in an ovarian tumor even in the absence of usual ectodermal elements and sebaceous secretions.
The percentages of males with different developmental stage of testes and different conditions of the ectodermal sac were analyzed using the generalized linear model with binomial distribution and the link function logit.
Hannah Farris, an otherwise normal and happy fourteen-year-old, suffers from Ectodermal Dysplasia, a rare medical condition that won't allow her to grow adult teeth.
The other pool of thought is that germinal cell neoplasms originate from remnants of the primitive streak which fails to differentiate among mesodermal, ectodermal and endodermal tissues in the embryonic disc (7).
9In mammalian hair follicles development there is reciprocal induction between ectodermal epithelium and mesodermal mesenchyme.