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.