The fine structure of the intra-uterine epithelium during late gestation in the blue shark,Prionace glauca

The fine structure of the intra-uterine epithelium of the pregnant blue shark,Prionace glauca, was examined. The intra-uterine epithelium was bilaminar and the underlying epithelial cell was extremely reduced in cytoplasm. Two cytological characteristics were shown in the outer epithelial cell; open inter-cellular spaces closed in the apical portion by a junction complex and, numerous mitochondria distributed in the basal and lateral portions of the cytoplasm. Secretive characteristics were not recognized in the outer epithelial cell, although few regions composed only of mucous cells were seen. The flattened endothelium of the capillary lay closely beneath the epithelium. These structures are thought to facilitate the water-solute transport and gaseous exchange. It suggests that the intra-uterine epithelium is involved in the osmoregulation of the uterine fluid and the exchange of respiratory gases between mother and fetus.