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.

The mediobasal hypothalamus in the human fetus. Studies on neurovascular link by Golgy-Cox technique.

There is a remarkable parallel between the development and maturation of the nervous cells and that of the vascular elements in the human fetus. By the Golgy method the hypophysiotrophic area appears to be uniformly populated by small multipolar neurons within the loops of the primary capillary plexus. Only in the 80 mm embryo did we find bipolar neurons, whose processes are directed to the 3rd ventricle and respectively to the median eminence (ME).

The development of the hypothalamo-hypophysial portal system in human fetus.

In the earliest stages of development of the nervous system, the hypophysial stalk has a horizontal disposition (having, above the hypothalamus and below the anterior lobe of the hypophysis, a group of cells placed in the sella turcica). The stalk becomes vertical in the VI--VII month of fetal life. Until the stage corresponding to the length of 92 mm vertex--coccis of the fetus, few blood vessels are to be found in this region; they follow the stalk's direction.