[Experimental and histologic studies on fetal membrane tensility and membrane rupture]

The collagen microfibrils of the amniotic connective tissue are irregularly textured. In all a preference for a meridional orientation perpendicular to the placental-rim can be observed. There are randomly dispersed weak spots between dense bundles of collagen fibres. The chorion connective tissue consists also of fibril bundles in a meridional main orientation. Within the bundles or bands there is an unmistakable pattern of latticed arranged fibrils. The framework receives its stability from the bundles that run perpendicular or inclined to the previously mentioned bundles. There are randomly dispersed weak areas between the dense fibril aggregates. In general the amniotic and chorionic connective tissues are both of variable strength. The tensile strength of both membranes is regionally varying due to the irregular texture. At times it varies within the same fetal membrane or from fetal membrane to fetal membrane considerably, where by the variation in membrane thickness also is of influence. It is to be observed that in general the resistance perpendicular to the meridian direction is smaller than along the meridian direction. During the rupture of the membranes the latticed arranged fibres from the bundles of the chorionic connective tissue give way and tear in an arbitrary weak spot. In the amniotic tissue the tearing also begins in a weak spot and continues to tear in a non predictable direction between the irregular pattern of bundles.