An equivalent of the paraventricular organ in the human fetus

Serial sections of the hypophyseal-hypothalamic region processed by the Golgi-Cox and hematoxylin-eosin staining methods show features of the third ventricular wall which suggest the existence in the human fetus of an equivalent of the paraventricular organ, described in other species. In a 28 cm vertex-coccis long human fetus, there is a caudal extension of the infundibular recess that extends into the neural lobe of the hypophysis. This extension takes the shape of successive dilatations intercommunicating by narrow channels, lined by a thicker ventricular ependyma. Cellular processes, free in the cerebro-spinal fluid, form a supraependymal layer. A rich vascular network may be observed in the region to the modified ependyma.