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Abstract

A schematic plan of late developmental organization of the fetal cotyledonary elements of the hemochorial placenta is presented. It involves mechanical shaping by hemodynamics and stretching of the elements involved in the late chorion frondosum stage after the 2nd month of gestation. The result is the fetal cotyledon as described by Wilkin. The components of the fetal cotyledon are derived from differentiated vascular elements in tertiary stem, or anchoring, villi and vascular elements of the blastoderm which are formed by the twenty-first day after ovulation.