Blood Vessels of the Hypophysis
A prominent vascular supply ensures the coupling of the nervous and endocrine parts of the hypophysis. The afferent vessels, the superior hypophysial artery (E9) and the infe-rior hypophysial artery (E10), branch off fromthe internal carotid artery. The two superior hypophysial arteries form an arterial ring around the proximal part of the infun-dibulum, from where small arteries extend through the adenohypophysial cover into the infundibulum and disperse into portalcapillaries (E11). The recurrent limbs of thelatter collect in the portal veins (E12), which transport the blood to the capillary bed of the adenohypophysis. The trabecular arteries (E13) extend to the adenohypophysis, as-cend caudally, and supply the distal seg-ment of the infundibulum. The blood then runs from the capillary bed of the adenohypophysis into the veins.
The two inferior hypophysial arteries supply the neurohypophysis; with several branches in the area of the intermediate part, they also form special vessels (E14); from here, the blood also runs via short portal vessels into the capillary bed of the adenohypophysis.
Thus, the adenohypophysis receives no direct arterial supply. The latter goes into the infundibulum and into the neurohy-pophysis, from where the blood flows into the adenohypophysis via the portal vessels and, only then, drains into the venous side (E15) of the circulation.