[New data on the morphology of the allanto-chorion fetal membranes]

The authors have carried out an electron microscopic study on the morphology of the allanto-chorial membranes of late pregnancy. The demonstration of these amniotic cells with their long pedicles which resemble those of renal podocytes, together with the presence of intercellular canals lined by long villi which themselves cross over with one another to make a grid, and the existence of intracellular canals that make transcytoplasmic tunnels, permit the authors to suggest that they are dealing with a morphological illustration of ultrafiltration processes. The authors suggest that the forces that bring about plasma filtration from the intervillous chamber towards the amniotic compartment crossing the allanto-chorial membranes are the same as those that cause glomerular filtration. These are hydrostatic pressure in the intervillous chamber and the oncotic pressure within the amniotic compartment.