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Changes In Absorptive Surfaces Of Rat Visceral Yolk Sac With Increasing Gestational Age, W. P. Jollie

Scanning Electron Microscopy

The free surface of the endodermal epithelial lining of the rat visceral yolk sac was examined by scanning electron microscopy at three stages of pregnancy, viz., 12, 17 and 22 days (birth typically occurring on the 23rd day). Additionally, by ultrasonic vibration of tissues that had been subjected to prolonged osmium fixation, the epithelium was removed and such microdissected membranes similarly were examined.

With increasing gestational age the free surface of the epithelium. underwent a relative increase in absorptive area by three mechanisms: formation of increasingly complex villous projections of the visceral yolk sac as a whole, a doming of …