Morphological aspects of the pharyngeal hypophysis in human embryos

In human embryos the hypophyseal sac (Rathke's pouch) originates at the roof of the mouth until stage 15 as a broad rim. As the mandibular arch and the maxillary swelling enhance the mesodermal masses in forming the early palatal shelves the rim is reduced to a cleft of about 0.2 mm in broadness in stage 17. From stage 18 up to stage 23 there is a prominent papilla in the midline of the mouth's roof which later on may become recanalized. The different SEM-aspects of the pharyngeal hypophysis are demonstrated.