feeder layernutritive layerouter cell masstrophoblastic layertrophodermvegetative layer滋养: nourish层: I storey; tier; stratum合胞滋养层: plasmodi-trophoblast合体滋养层: syncytiotrophoblast; syntrophoblast基质滋养层: stroma feeder layer下载手机词典可随时随地查词查翻译