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. These vessels originate from a vascular network which lies in the post-tuberal region being also considered the origin of a "special" kind of vessel observed very early in the hypophysis development. The veins can be found later at the 140 mm vertex-coccis fetus. Their structure is much like the structure of the portal vessels in the adult. At their proximal end their aspect can be referred to as an anastomotic arterio-venous system. After 7 months of development the vessels resemble their adult form, being however less numerous.