Morphological Development of the Human Hypophysis

= Abstract = The morphological development of the human hypophysis was studied using 142 developing human hypophyses from 19 embryos and 123 fetuses. The adenohypophysis first developed at 4 weeks of gestational age as an upward growing fold of the primitive oral ectoderm Rathke's pouch. At 7 weeks, the configuration of pars distalis and pars intermedia was formed. The Rathke's pouch lost its connection with the oral cavity completely at 8 weeks. Pars tuberalis became evident at 9 weeks. Histologically, capillary formation was found at the end of 7 weeks in adenohypophysis and basophilic lamellated bodies were first identified at 8 weeks. Cells with eosinophilic cytoplasm appeared at 9 weeks and those with basophilic cytoplasm appeared between 10-12 weeks. The neurohypophysis developed as a downward evagination of the diencephalic floor at 6 weeks. After 9 weeks, capillary formation occurred in the stroma, and primitive neuroepithelial cells became differentiated. Ependymal tubules were also observed at this time. Between 25-29 weeks, suspicious pigment was seen in the cytoplasm of pituicytes and glial cell modification into pituicytes seemed completed. No Herring body-like structures could be identified throughout the fetal period.