/blas"teuh sist/, n. Embryol.
the blastula of the mammalian embryo, consisting of an inner cell mass, a cavity, and an outer layer, the trophoblast.
[1885-90; BLASTO- + -CYST]

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▪ embryo phase
      a distinctive stage of a mammalian embryo. It is a form of blastula that develops from a berrylike cluster of cells, the morula. A cavity appears in the morula between the cells of the inner cell mass and the enveloping layer. This cavity becomes filled with fluid. The blastocyst differs from the blastula in that it is composed of two already differentiated cell types, the inner cell mass and the enveloping layer.

      Further differentiation produces a thin layer of cells, called the hypoblast, between the inner cell mass and the cavity. These cells contribute to the formation of the embryonic endoderm, from which derive the respiratory and digestive tracts.

      The enveloping layer is now referred to as the trophoblast. It does not contribute directly to the formation of the embryo but rather serves to establish a connection with the maternal uterus. It is a precursor of the placenta.

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Universalium. 2010.

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Look at other dictionaries:

  • Blastocyst — Blas to*cyst, n. [Gr. blasto s sprout + E. cyst.] (Biol.) The germinal vesicle. [1913 Webster] …   The Collaborative International Dictionary of English

  • blastocyst — (n.) 1876, from BLASTO (Cf. blasto ) + CYST (Cf. cyst) …   Etymology dictionary

  • blastocyst — [blas′tōsist΄, blas′təsist΄] n. [ BLASTO + CYST] BLASTULA …   English World dictionary

  • Blastocyst — Infobox Embryology Name = Blastocyte Latin = GraySubject = GrayPage = Caption = Caption2 = System = CarnegieStage = 3 Days = 5 Precursor = GivesRiseTo = MeshName = Blastocyst MeshNumber = A16.254.085 DorlandsPre = b 14 DorlandsSuf = 12187695 The… …   Wikipedia

  • Blastocyst — A stage in the early embryonic development of mammals in which there is a hollow sphere with an outer layer of cells and inside the hollow sphere, there is a cluster of cells called the inner cell mass. If development continues, the outer layer… …   Medical dictionary

  • blastocyst — n. an early stage of embryonic development that consists of a hollow ball of cells with a localized thickening (the inner cell mass) that will develop into the actual embryo; the remainder of the blastocyst is composed of trophoblast . At first… …   The new mediacal dictionary

  • blastocyst — In mammalian development, cleavage produces a thin walled hollow sphere, whose wall is the trophoblast, with the embryo proper being represented by a mass of cells at one side. The blastocyst is formed before implantation and is equivalent to the …   Dictionary of molecular biology

  • blastocyst cavity — blastocystic cavity the fluid filled cavity developing in the morula as it becomes a blastocyst …   Medical dictionary

  • blastocyst — noun Date: circa 1881 the modified blastula of a placental mammal having an outer layer composed of the trophoblast …   New Collegiate Dictionary

  • blastocyst — n. [Gr. blastos, bud; kystis, bladder] (PLATYHELMINTHES: Cestoda) In Trypanorhynca, a posterior bladder of the metacestode into which the body is withdrawn …   Dictionary of invertebrate zoology

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