MEDICAL EMBRYOLOGY 502
Lecture 2 Summary

Abnormalities associated with the first week
  1. Failure of the embryo to attach
  2. Attachment at the wrong uterine site (placenta previa)
  3. Ectopic pregnancy
Highlights of the first week of development
  1. In the uterine tube, the fertilized ovum (zygote) undergoes a series of mitotic divisions (cleavage) within the confines of the zona pellucida. A solid ball of cells results - the morula.
  2. The morula enters the uterine cavity and is transformed into a blastocyst composed of an outer layer of trophoblast cells, a fluid-filled cavity (blastocoele), and the inner cell mass (embryoblast).
  3. The blastocyst sheds its zona pellucida and attaches to the uterine epithelium via the polar trophoblast cells.
Copyright 1999 The University of Michigan
Unauthorized use prohibited.
Please send comments to Dr. Tom Gest (gest@umich.edu)
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