Ectoderms definition of Ectoderms in the Free Online Encyclopedia.

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 endoderm endoderm , 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 Porifera Porifera [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. , Ctenophora Ctenophora , a small phylum of exclusively marine, invertebrate animals, commonly known as sea walnuts or 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
..... Click the link for more information. , and Cnidaria Cnidaria 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 Echinodermata Echinodermata [Gr.,=spiny skin], phylum of exclusively marine bottom-dwelling invertebrates having external skeletons of calcareous plates just beneath the skin.
..... Click the link for more information. and Chordata Chordata , 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
..... Click the link for more information. , a third, middle layer, the mesoderm mesoderm, 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 Mollusca Mollusca , 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 Annelida Annelida [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 [′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.

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.

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Ectoderm (redirected from Ectoderms)

Ectoderm
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