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Definition of "amnion" []

  • A thin, tough, membranous sac that encloses the embryo or fetus of a mammal, bird, or reptile. It is filled with a serous fluid in which the embryo is suspended. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Use "amnion" in a sentence
  • "In these three classes alone we find the remarkable embryonic membrane, already mentioned, which we called the amnion; a cenogenetic adaptation that we may regard as a result of the sinking of the growing embryo into the yelk-sac."
  • "They described primitive cells found in a part of the placenta called the amnion, which they coaxed into forming a variety of cell types and which look very similar to sought-after embryonic stem cells."
  • "—The amnion is a membranous sac which surrounds and protects the embryo."