from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. The outermost layer of cells of the blastocyst that attaches the fertilized ovum to the uterine wall and serves as a nutritive pathway for the embryo. Also called trophoderm.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. The membrane of cells that forms the wall of a blastocyst during early pregnancy, providing nutrients to the embryo and later developing into part of the placenta.

from The Century Dictionary and Cyclopedia

  • n. An external epiblastic layer that does not enter into the formation of the embryo, but does take an active part in nutritional processes intended for it; the blastocystic ectoderm.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. the membrane that forms the wall of the blastocyst in early development; aids implantation in the uterine wall


tropho- + -blast (Wiktionary)


  • A typical day-5 human embryo consists of 200-250 cells, most of which comprise the trophoblast, which is the outermost layer of the blastocyst.


  • In a healthy pregnancy, cells that come from the embryo's placenta-called trophoblast cells-move into the walls of the uterus and help to open up maternal arteries, thereby increasing the available blood and nutrient supply.

    Slate Articles

  • Perhaps they're hoping the the terms "trophoblast", "blastocoel", and "blastocyst" will disguise the fact that we're talking about a human being?

    A Doctor's Perspective on Stem Cell Research

  • In most of these diseases, the diagnosis can be made by genetic analysis of cultured trophoblast cells derived from CVS.

    In Utero Stem Cell Transplantation

  • Johnson MP, Childs MD, Isada NB, Koppitch III GC, Evans MI: Trisomy 16 CVS and viable pregnancy: Lethal aneuploidy compartmentalized to the trophoblast in two otherwise normal pregnancies.

    Prenatal Diagnosis

  • In a 2009 French study at the University of Caen, scientists discovered that glyphosate can kill the cells in the outer layer of the human placenta (the trophoblast membrane), which in turn can kill the placenta.

    Jeffrey Smith: Genetically Modified Soy Diets Lead to Ovary and Uterus Changes in Rats

  • Researchers analyzed trophoblast cells from the placenta from 40 pregnant women about to undergo surgery for ectopic pregnancy, miscarriage or abortion.

    Getting Closer to the Root of What Causes Baldness

  • Caveat: Technical difficulties plus contamination of some uterine samples prevented collection of trophoblast cells from every patient.

    Getting Closer to the Root of What Causes Baldness

  • The derivation of HESC cultures requires the removal of the trophoblast.


  • That there is some intercellular coordination in the zygote is revealed by the fact that the development of the early embryo requires that some cells become part of the trophoblast while others become part of the inner cell mass.



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  • "The cells of the morula are at first closely aggregated, but soon they become arranged into an outer or peripheral layer, the trophoblast, which does not contribute to the formation of the embryo proper, and an inner cell-mass, from which the embryo is developed."
    - Henry Gray, 'Anatomy of the Human Body', 1918.

    September 20, 2009