Electron microscopic observations of the differentiating processes of the tracheal mucosa in various fetal stages have been done mostly on experimental animals, but scarcely on human fetuses. In this study, the differentiating processes of the tracheal mucosa of human fetuses aged from 6th week to 23rd week of gestation were observed using scanning and transmission electron microscopes. Results obtained were as follows:
1. Ciliated cells appeared at 8th week of gestation in the membranous portion of the trachea, but in the cartilaginous portion of the trachea, the appearance of ciliated cells was at 14th week of gestation. After 15th week of gestation, the number of ciliated cells increased rapidly in both the membranous and cartilaginous portions of the trachea.
2. Primary cilia were observed at 8th and 10th week of gestation in the membranous portion of the trachea, and at 10th week of gestation in the cartilaginous portion of the trachea. Among these primary cilia, very long ones (approximately 7μ length) which had never been found in experimental animals, could be observed.
3. In fetus at 11th week of gestation, immature goblet cells appeared. After 14th week of gestation, goblet cells possessed many typical secretory granules.
4. Glycogen cells containing abundant glycogen granules within the light area of their cytoplasm were mostly observed at 8th and 10th week of gestation, and then the number of these cells decreased gradually. After 18th week of gestation, glycogen cells disappeared. These glycogen cells were supposed to be tentative features in the course of cell lysis.
抄録全体を表示