The hypophysis of Monodelphis domestica (Marsupialia): the state of organ development and cell differentiation in the adenohypophysis on different days post partum

In the newborn gray short-tailed opossum, Monodelphis domestica, the fusion of the neurohypophysis and adenohypophysis has not finished. A compression of the adenohypophyseal vesicle is exerted by the neurohypophysis. The latter, as can be seen in a 12-day old specimen, finally, will be almost completely wrapped into the adenohypophysis. The adenohypophysis of the newborn and early pouch-young shows substantial growing on the basis of mitoses mainly in the pars intermedia, but in the pars distalis, too. Cytodifferentiation in the newborn, light microscopically, is indicated by an increasing heterogeneity of cell morphology which is most obvious in the cranial and caudal regions of the median sections. Electron microscopically, the presence of small quantities of granules as well as small quantities of golgi membranes and ribosomal endoplasmic reticulum, respectively, gives evidence of a beginning synthesis activity in the newborn.