Developmental Anatomy

Stage 3: Lab Manual - Horizon III Free Blastocyst

First view Second view

  • 0.1 - 0.2 mm in diameter.
  • The trophoblastic cells that form the walls of the cavity multiply more rapidly than the embryonic cells of the inner cell mass.
  • The zona begins to disappear.
  • Ovulation age: 4 - 5 days.

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Developmental Stages in Human Embryos by Ronan O'Rahilly and Fabiola Müller.
Published by Carnegie Institution of Washington, Publication 637. 1987.

Stage 3 (PDF 71 KB)


QUESTION: Which type of cells multiply most rapidly?