ONTOGENIC AND PHYLOGENETIC EVALUATION OF THE PRESENCE OF FIBRIN-TYPE FIBRINOID IN THE VILLOUS HAEMOCHORIAL PLACENTA

The hypothesis that fibrin type fibrinoid deposition on villi is uniqu e to the term human placenta was tested. Bright-field microscopy was u sed to examine sections of first and second trimester human placental villi and tissues from three animal species that have villous haemocho rial placentae similar to the human: the armadillo, the baboon and the rhesus. Sections stained with haematoxylin and eosin showed fibrin ty pe fibrinoid deposits were hypocellular, eosinophilic masses attached to the surface of villi examined from both the human and the animal sp ecimens. The deposits were located at discontinuities in the syncytiot rophoblast layer and the fibrinoid provided a matrix for trophoblast r e-epithelialization of the villous surface. It is concluded that fibri n-type fibrinoid is not unique to the term human placenta. The presenc e of the syncytiotrophoblast discontinuities associated with the fibri noid deposition must be considered in models of maternal-fetal exchang e in the villous haemochorial placenta. (C) 1997 W.B. Saunders Company Ltd.