[Morphologic features of the extraembryonic organs after ischemic damage to the yolk sac].

An opinion on membrane organs as a united reacting system is motivated. Ischemia of the rat yolk sac is chosen as the model of the disturbance. In parallel to the yolk sac involution size of the nuclei, nucleoli, cytoplasm in the cytotrophoblast elements and the simplast nuclei of the labyrinth bars in the allantoic placenta increase, while the size of the nuclei in the amniotic and exocelomic epithelium of the amnion and of the exocelomic epithelium of the visceral leaf in the yolk sac decreases. Embryonic death increases and by the end of pregnancy reaches 20%. Description of the structural changes in the yolk sac, in the allantoic placenta with its entodermal component and in the amnion are presented. Volume of the amniotic fluid decreases by 35-50%. It is suggested that the amnion is functioning in interaction with the yolk sac, the latter makes the morphological unity with allantoic placenta.