[Ultrastructural study of human yolk sac].
Twenty cases of human yolk sac of different gestation weeks observed by electron microscopy. The wall of yolk sac consisted of endoderm, mesenchyme and mesothelium. Nuclei of the endodermal cell were large and nucleoli were remarkable. The surface of endodermal cell presented a number of microvilli. There were Golgi complex, rough endoplasmic reticulum, glycogen and mitochondria in the cytoplasm of the endodermal cell. The fibroblast-like cell, macrophage-like cell. erythroblast in various mature degree, collagen filament and capillaries were found in the mesenchyme. The mesothelial cell had long, slender microvilli, which were mostly branched. Pinocytotic vesicles in the apical cytoplasm beneath the mesothelial cell membrane were frequent. The differently sized endodermal tubules with well-defined lumen and microvilli were recognized by electron microscopy. Masses of endodermal cells frequently invaginated in the mesenchymal layer, and they often reached the mesothelial layer. These structures of yolk sac were the foundation of finishing synthesis, secretion, translation and hematopoiesis during early organogenesis.
Wang
Y
Y
Second Affiliated Hospital.
Yang
G
G
Zeng
M
M
Wang
Y
Y
D005260:Female; D006801:Humans; D008854:Microscopy, Electron; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D015017:Yolk Sac / Q000648:ultrastructure*