[Problems of distinction of normal, arteficial and pathological structures in mature human placental villi. I. Ultrastructure of the syncytiotrophoblast (author's transl)].

Thirty-four mature human placentae were punctured in situ during cesarean section and fixed immediately. The ten cases which seemed normal according to clinical and morphological criteria were examined electron-microscopically. Findings won in ideal conditions after perfusion fixation of the guinea-pig placenta were compared to the human punction samples. The granular endoplasmic reticulum in the syncytium proved to be the most susceptable parameter. Its cisternae are narrow and arranged parallel to each other after optimal fixation. The larger the ischemic phase--already detectable after 2 min--, the more disorientated and dilated they become. The mitochondria only react considerably later. Similar structural alterations also occur in the course of pathological processes. The meaning of arteficially and pathologically induced ultrastructural changes and their interdependance are discussed.