Carnegie J A, McCully M E, Robertson H A
Am J Anat. 1985 Dec;174(4):471-88. doi: 10.1002/aja.1001740409.
During the period of rapid elongation prior to the initiation of placental attachment (days 12-16 of gestation), the ovine blastocyst consists of a single layer (primarily) of roughly cuboidal trophoblastic cells with an inner lining of flattened endodermal cells. Well-developed spot desmosomes link the adjacent cell borders in both the trophoblastic and endodermal layers. The trophoblastic cells contain acid phosphatase-positive, lysosomelike organelles, the mean diameter of which increases greatly between days 12 and 16 and whose contents vary during development. Also during the developmental period studied, trophoblast cells accumulate lipid; and periodic acid-Schiff-positive binucleate cells appear within the trophoblast layer. A consistent observation throughout the 5 days of rapid growth and differentiation of the blastocyst was the death and disintegration of some trophoblast cells. These disintegrating cells are usually singly dispersed within the trophoblast, although occasionally groups of four or five are observed. The cell death may indicate overall remodelling of the blastocyst, or the cells may represent genetically deficient cells which are unable to respond to the appropriate signal to differentiate.
在胎盘附着开始前的快速伸长阶段（妊娠第12 - 16天），绵羊囊胚由单层（主要是）大致立方形的滋养层细胞组成，其内部衬有扁平的内胚层细胞。发育良好的点状桥粒连接着滋养层和内胚层的相邻细胞边界。滋养层细胞含有酸性磷酸酶阳性的溶酶体样细胞器，其平均直径在第12天至16天之间大幅增加，且其内容物在发育过程中有所变化。同样在研究的发育阶段，滋养层细胞积累脂质；并且在滋养层内出现过碘酸 - 希夫阳性的双核细胞。在囊胚快速生长和分化的5天中始终观察到的一个现象是一些滋养层细胞的死亡和崩解。这些崩解的细胞通常单个分散在滋养层内，尽管偶尔会观察到四五个细胞组成的群体。细胞死亡可能表明囊胚的整体重塑，或者这些细胞可能代表无法对适当的分化信号做出反应的基因缺陷细胞。
