Ellington S K
Physiological Laboratory, Cambridge.
J Anat. 1987 Feb;150:247-63.
The morphology of the developing chorion of the rat has been studied from its initial formation from the extra-embryonic region of the amniotic fold until its fusion with the ectoplacental cone and allantois prior to the development of the chorio-allantoic placenta (that is from 8.25 to 10.25 days of gestation). The gross structural changes, the mitotic indices, the ultrastructure and the distribution of carbohydrate in the mesodermal and ectodermal cells of the chorion have been studied throughout this period of development. The chorion developed to form a diaphragm across the egg cylinder, separating the exocoelom from the ectoplacental cavity. With further development, the ectoplacental cavity became smaller until the chorion was lying against the ectoplacental cone, to which it fused. The mesodermal cells of the chorion formed a single layer of cells covering the ectodermal cells. Shortly before the fusion of the chorion with the ectoplacental cone or the allantois, the integrity of the mesodermal cell layer in the central region of the chorion was disrupted. Intercellular contact was lost and the mesodermal cells rounded up exposing the PAS-positive extracellular coat of the ectodermal cells. The allantois was only seen to fuse with the chorion in regions in which the ectodermal cells were exposed. It was suggested that the glycocalyx of the ectoderm cells may be of importance in the fusion of the allantois and chorion.
大鼠发育中绒毛膜的形态学已从其在羊膜褶的胚外区域开始形成，一直到绒毛膜尿囊胎盘发育之前与外胎盘锥体和尿囊融合（即妊娠8.25至10.25天）进行了研究。在整个发育期间，研究了绒毛膜中胚层和外胚层细胞的总体结构变化、有丝分裂指数、超微结构以及碳水化合物的分布。绒毛膜发育形成一个横跨卵圆柱体的隔膜，将外体腔与外胎盘腔隔开。随着进一步发育，外胎盘腔变小，直到绒毛膜贴靠在外胎盘锥体上并与其融合。绒毛膜的中胚层细胞形成覆盖外胚层细胞的单层细胞。在绒毛膜与外胎盘锥体或尿囊融合前不久，绒毛膜中央区域的中胚层细胞层完整性被破坏。细胞间接触丧失，中胚层细胞变圆，露出外胚层细胞的PAS阳性细胞外被。仅在暴露外胚层细胞的区域观察到尿囊与绒毛膜融合。有人提出，外胚层细胞的糖萼可能在尿囊和绒毛膜的融合中起重要作用。
