Collagen III (Reticulin) â A Location Marker of Pre-Sinusoid ArterioleSphincters in the Villous System of Human Placenta

Blood micro-circulation within the placental villous system still raises a large number of problems of functional anatomy concerning the angio-structure of terminal villi, the communication between arterioles and venules of the umbilical vascular system, the spatial extension of the “extra-vascular contractile system” and, last but not least, the existence of the pre-sinusoid arteriole sphincters. The authors make a micro-anatomic analysis of the spatial distribution of the collagen fibres type III (reticulin) as markers of the pre-sinusoid arteriole sphincters. The study was performed on 20 human placentae of gestation age between 25 and 35 weeks. After paraffin embedding, 10 serial sections were obtained from each paraffin block. They were stained in Hematoxilin Eosin, or silver-impregnated according to Gomori method. We had two objectives: to evaluate the spatial distribution of post arteriole sinusoid blood vessels within the terminal villi in the placenta, on the one hand, and the visualization of the location of a presinusoid arteriole sphincter system, on the other. The authors believe that umbilical arterioles and venules are connected “serially” at the level of terminal villi through arteriole-venule sinusoid blood vessels. The location of the trajectory of collagen type III (reticulin) bundles enveloping pre-sinusoid arterioles are markers of the existence of a pre-sinusoid arteriole sphincter at this level.