[The dynamics of the amniotic fluid]

Morphological study of the ovular membranes showing that under the amnion, until term, there persists perfectly live and active chorial cytotrophoblast covered by a well vascularised and developed parietal decidua. Under the electron microscopy, the apical pole of the amniotic cells as well as their intercellular space are bordered by microvilli. Their basal pole has squat pedicels. The chorion which supports the amnion is avascular. The surface of the cytotrophoblast opposite the chorio-amnion is raised by numerous protuberances in the form of pedicels. The trophoblast is also furrowed by intercellular canals bordered by microvilli and reinforced by desmosomes. Two cellular appearances may be distinguished in the trophoblast: elements similar to the syncytial type with the characteristics of steroid cells and elements of a Langhans type which may play a role in protein synthesis. The decidual cells, in a quinconcial perivascular arrangement, are rich in pinocytotic vesicles. Thus whilst it is undeniable that the foetus plays a certain role in the dynamics of the amniotic fluid by swallowing and urinary excretion, these phenomena are minimal in relation to exchanges through the ovular membranes. Transamniotic passage is the first stage in movement of the fluid. The chorion, by virtue of its plexiform, areolar structure forms the next stop. From the chorion, the circulation continues through the intercellular canals of the trophoblast and the amniotic fluid is thus brought into the well vascularised parietal decidua. In addition to this extracellular circulation, the authors fell that there exists an intracellular passage by uptake and secretion, as evidenced by the high degree of pinocytosis within the cells.