Sự tồn tại của phôi thai eutherian / thai nhi phụ thuộc vào sự hình thành của một cơ quan thoáng qua nhưng quan trọng, nhau thai. Placentation là thử nghiệm đầu tiên của năng lực differentiative và organogenic của conceptus. Trong quá trình này, các tế bào chuyên biệt của nhau, gọi là lá nuôi phôi, | Chapter 87 Vascular Transformation of Placental Cytotrophoblasts Susan J. Fisher University of California-San Francisco San Francisco California Survival of the eutherian embryo fetus depends on formation of a transient but vital organ the placenta. Placentation is the first test of the differentiative and organogenic capacity of the conceptus. During this process the placenta s specialized cells termed trophoblasts acquire many unusual properties. For example one population of mononuclear cells termed cytotrophoblasts CTBs deeply invades the uterine wall. Invasion accomplishes two critical goals attaching the embryo to the uterus and diverting maternal blood flow to the placenta thus enabling effective gas nutrient and waste exchange. The molecular underpinnings of this complex process require the precise coordination of intricately timed differentiation programs executed by both placental and uterine cells for reviews see Refs. 1 2 . This chapter focuses on the profound changes in trophoblast phenotype that occur during CTB invasion of the uterus. Data gathered from the studies we review point to the central importance of molecules that control the intimate relationship that develops between fetal CTBs and the maternal vasculature. These findings have important implications for understanding mechanisms of placentation and point to possible therapeutic strategies for remodeling other vascular beds. Morphological Aspects of Human Placentation The complex anatomy of the placenta has made studies of the entire organ difficult. Commonly the placenta is depicted as a simple pancake-shaped sponge connecting the embryo fetus to the uterus. This portion of the placenta which is expelled from the uterus during delivery is easy to obtain and consequently frequently studied. But the most interesting part of the placenta is rarely seen. This portion which lies buried within the uterine wall separates from the rest of the placenta during pregnancy termination or delivery. As a
