| Axons from neurons in the surge center and the tonic center extend to the stalk region where their endings terminate upon blood vessels of the hypothalamo-hypophyseal portal system. This portal system consists of: the superior hypophyseal artery; the primary portal plexus, (where the surge center and tonic center neurons terminate); the medial hypophyseal artery that supplies part of the anterior lobe of the pituitary (AL); the portal vessels that transport blood containing releasing hormones; and the secondary portal plexus that delivers blood (and releasing hormones) to the cells of the anterior lobe. MHA = Medial Hypophyseal Artery PPP = Primary Portal Plexus PV = Portal Vessels SHA = Superior Hypophyseal Artery SPP = Secondary Portal Plexus The photograph at the right is a scanning electron micrograph of the hypothalamo-hypophyseal portal system after vascular injection with latex (Mercox). It was provided with permission by Dr. H. Duvernoy, Faculte de Medecine et de Pharmacie de Besancon, Laboratoire d’Anatomie, Place St. Jacques, 25030 Besancon, France. |