The development of the human placental villous tree

Abstract

The present investigation was undertaken in order to achieve a better understanding of the dynamics of placental villous differentiation. Villous trees from human placentas from different stages of pregnancy (first trimester to full term) were isolated and studied by light microscopy and scanning electron microscopy. For light microscopy the trees were serially sectioned and two-dimensionally reconstructed. For scanning electron microscopy complete villous trees or freeze-cracked villi were studied. The most important finding was that the mesenchymal villi are continuously newly formed out of the trophoblastic sprouts throughout pregnancy. Because of this they exist in all stages of pregnancy and have to be considered the basis for growth and differentiation of the villous trees. In the first two trimesters they are the forerunners of the immature intermediate villi, whereas in the last trimester the mesenchymal villi are transformed into mature intermediate villi. The immature intermediate villi formed during the first two trimesters are developmental steps towards the stem villi. On the other hand, the mature intermediate villi, which only are developed during the last trimester, produce numerous terminal villi. The latter are not active outgrowths caused by proliferation of the trophoblast, but rather passive protrusions induced by capillary coiling due to excessive longitudinal growth of the fetal capillaries within the mature intermediate villi.

The Distribution of Laminins and Fibronectins Is Modulated During Extravillous Trophoblastic Cell Differentiation and Decidual Cell Response to Invasion in the Human Placenta

“…Other terms such as "sparse" or "specks" vs "rich" or "extensive" immunoreactivity were used to describe the distribution of the immunoreactivity. Nomenclature for placental structures has been adopted from Benirschke and Kaufmann (1990) and Castellucci et al (1990). The zones of anchoring cell columns (proliferative, matrix deposition, and invasion zones; see above) are adapted from Damsky et al (1992) and Frank et al (1994).…”

The Morphology of Villous Capillary Bed in Normal and Diabetic Placenta

“…They are precursor villi of mature intermediate villi, which branch subsequently into terminal villi. At the end of pregnancy, terminal villi represent more than one half (55%) of the total number of villi (Castellucci et al 1990;Benirschke & Kaufmann, 1995;Kingdom et al, 2000;Challier et al, 2001). …”

Three-dimensional digital reconstruction of human placental villus architecture in normal and complicated pregnancies

“…Analogous approaches were used with some success by Castelucci and co-workers who created 2D spatial reconstructions of stem villous histoarchitecture based on serial section photographs (14).…”