Moxey P C, Trier J S
Anat Rec. 1979 Nov;195(3):463-82. doi: 10.1002/ar.1091950307.
We describe the sequential ultrastructural changes in villus absorptive cells of human fetal small intestine between 9 and 22 weeks of gestation. In concert with villus formation at 9 to 10 weeks, a complex membranous system designated the apical tubular system appeared in the apical cytonous system designated the apical tubular system appeared in the apical cytoplasm of absorptive cells. The apical tubular system consisted of deep invaginations of plasma membrane and membrane-bounded vesicles and tubules. Some elements of this system were characterized by linear arrays of particles on the inner (luminal) membrane leaflet. After villus formation, many lysosomal elements designated "meconium corpuscles" also appeared in the apical cytoplasm. Modified morphometric studies suggested that both the apical tubular system and the lysosomal elements were more extensively developed in the distal than in the proximal intestine, were most abundant at 15 to 17 weeks, and decreased by 18 to 22 weeks. Morhpometry also showed an inverse relationship between the relative surface density of the apical tubular system and microvillus membrane, suggesting the possible derivation of elements of the former from the apical plasma membrane. Exposure of intestine to ferritin for 8 to 40 minutes in vitro revealed ferritin in elements of the apical tubular system of 12- to 20-week fetuses. There was no evidence of transport of ferritin across absorptive cells. Distinctive membranous bodies composed of convoluted membrane-bound cisternae separated by narrow channels of cytoplasmic matrix were seen in the Golgi region and apical cytoplasm of fetal absorptive cells between 14 and 22 weeks. In a single 22-week fetus, there was marked proliferation of smooth endoplasmic reticulum, a decrease in cytoplasmic glycogen and loss of most lysosomal and apical tubular elements in the proximal but not the distal intestine. Thus, by the end of the second trimester, the structure of absorptive cells in proximal intestine was remarkably similar to absorptive cells in adult intestine.
我们描述了妊娠9至22周期间人胎儿小肠绒毛吸收细胞的连续超微结构变化。在9至10周时随着绒毛的形成，一个被称为顶端管状系统的复杂膜系统出现在吸收细胞的顶端细胞质中。顶端管状系统由质膜的深陷、膜结合的囊泡和小管组成。该系统的一些成分在内（腔）膜小叶上具有线性排列的颗粒。绒毛形成后，许多被称为“胎粪小体”的溶酶体成分也出现在顶端细胞质中。改良的形态计量学研究表明，顶端管状系统和溶酶体成分在远端小肠比近端小肠发育更广泛，在15至17周时最为丰富，并在18至22周时减少。形态计量学还显示顶端管状系统的相对表面密度与微绒毛膜之间呈负相关，表明前者的成分可能来源于顶端质膜。将小肠在体外暴露于铁蛋白8至40分钟后，在12至20周胎儿的顶端管状系统成分中发现了铁蛋白。没有证据表明铁蛋白穿过吸收细胞进行转运。在14至22周胎儿的吸收细胞的高尔基体区域和顶端细胞质中可见由被狭窄的细胞质基质通道分隔的卷曲膜结合池组成的独特膜性小体。在一个22周的单一胎儿中，近端小肠而非远端小肠出现了滑面内质网的显著增殖、细胞质糖原减少以及大多数溶酶体和顶端管状成分的丧失。因此，到妊娠中期结束时，近端小肠吸收细胞的结构与成人小肠吸收细胞非常相似。
