Blastoderm

Blastoderm

A Blastoderm is the layer of cells formed at one pole of the yolky egg of birds. The yolk prevents the division from taking place through the egg, resulting in meroblastic cleavage during the many cleavage divisions. At the pole containing less yolk, the ovum divides and subdivides, forming the blastoderm, which gradually spreads around the yolk and forms the embryo. The blastoderm is comprised of two layers, the epiblast and the hypoblast, which enclose the fluid-filled blastocoel cavity. This embryonic stage is the avian equivalent of birds.

ee also

*Embryology

References

*MW 1935|date=August 2008
* Campbell Reece, Biology 7th edition, Pearson Publishing, 2005


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  • blastoderm — blastodérm s. n., pl. blastodérme Trimis de siveco, 10.08.2004. Sursa: Dicţionar ortografic  BLASTODÉRM s.n. Membrană vitelină care dă naştere corpului embrionului. [< fr. blastoderme, cf. gr. blastos – germen, derma – piele]. Trimis de… …   Dicționar Român

  • Blastoderm — Blas to*derm, n. [Gr. blasto s sprout + E. derm.] (Embryology) the early stage of an embryo after the first cleavages of the ovum; also, the layer of cells of which the early embryo is composed; specifically: (a) the early embryo developing from… …   The Collaborative International Dictionary of English

  • Blastodérm — (Keimhaut), s. Entwickelungsgeschichte …   Meyers Großes Konversations-Lexikon

  • Blastoderm — ⇒ Blastula …   Deutsch wörterbuch der biologie

  • blastoderm — [blas′tōdʉrm΄, blas′tədʉrm΄] n. [ BLASTO + DERM] the part of a fertilized ovum that gives rise to the germinal disk from which the embryo develops blastodermic adj …   English World dictionary

  • blastoderm — In many eggs with a large amount of yolk, cell division (cleavage) is restricted to a superficial layer of the fertilized egg (meroblastic cleavage). This layer is termed the blastoderm. In birds it is a flat disc of cells at one pole of the egg… …   Dictionary of molecular biology

  • blastoderm — noun Etymology: German, from blast + derm Date: circa 1843 a blastodisc after completion of cleavage and formation of the blastocoel …   New Collegiate Dictionary

  • Blastoderm — 1 Morula, 2 Blastula Die Blastula (von griechisch Blastos: der Keim, die Knospe, der Spross) ist ein frühes Embryonalstadium Vielzelliger Tiere, das auf das Morula Stadium folgt und die Furchung abschließt. Im engeren Sinne wird als Blastula nur… …   Deutsch Wikipedia

  • blastoderm — early embryonic tissue composed of blastomeres arranged in a sheet like fashion; used to refer to embryonic tissue before embryonic axis formation …   Dictionary of ichthyology

  • blastoderm — n. [Gr. blastos, bud; derma, skin] The primary epithelium formed in early embryonic development of many invertebrates; germinal membrane …   Dictionary of invertebrate zoology

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