Ultrastructure of bovine placenta during all gestational period

ABSTRACT Placentas from pregnant cows with different gestation periods were used. Placental fragments of all groups were processed and evaluated by transmission electron microscopy. After fragment analysis, bovine placenta was observed to be epitheliochorial type in early pregnancy, becoming progressively sinepiteliocorial at the beginning of the second trimester. There are no ultrastructural evidences of inflammation in the region of caruncles throughout gestation, despite the invasion of caruncle proper lamina by trophoblast cells. However, throughout pregnancy and especially at the end, there were evident signs of cell degeneration in both trophoblast and the uterine epithelium. The active trophoblast cells intensely phagocytize cellular debris. There are complex interdigitations between the surface of the trophoblast and the uterine epithelium, which is related to the increase of the exchange surface between mother and fetus. At the end of pregnancy, interdigitations disappear, favoring the detachment and expulsion of the placenta after birth.

摘要 本研究采用不同妊娠期妊娠母牛的胎盘组织作为实验材料。对所有组别胎盘组织碎片进行处理后，通过透射电子显微镜（transmission electron microscopy）开展观察与评估。经碎片分析发现，牛胎盘在妊娠早期属于上皮绒毛膜型（epitheliochorial type），并在妊娠中期早期逐渐转变为合体上皮绒毛膜型。尽管滋养层细胞已侵入胎盘阜固有层，但整个妊娠期内胎盘阜区域均未出现炎症相关的超微结构证据。然而，在整个妊娠期，尤其在妊娠末期，滋养层细胞与子宫上皮均可见明显的细胞变性表现。活化的滋养层细胞可强效吞噬细胞碎片。滋养层细胞表面与子宫上皮之间存在复杂的相互嵌合结构，该结构与母胎间物质交换面积的增加密切相关。妊娠末期，该相互嵌合结构消失，有利于分娩后胎盘的脱离与排出。