Normal Villi (7-8 weeks) (40X)
Normal Villi (7-8 weeks) (40X)
 In the first trimester a complete layer of syncytiotrophoblast (blue arrow) surrounds the villus.  Beneath it lies a layer of cytotrophoblast (green arrow).  The fetal vessels occupy a small portion of the sectioned surface area of the villi.  The fetal vessels contain exclusively nucleated erythrocytes (black arrow) at this gestational age.
(Description By:Linda Ernst )
(Image Contrib. by:Linda Ernst UCHC )