Hypothalamic-Hypophysial Portal Blood Vessels of the Anterior Pituitary Gland The anterior pituitary is a highly vascular gland with
extensive capillary sinuses among the glandular cells. Almost all the blood that enters these sinuses
passes first through another capillary bed in the lower hypothalamus.
The blood then flows through small hypothalamichypophysialportal blood vessels into the anterior
pituitary sinuses. Figure 75-4 shows the lowermost portion of the hypothalamus, called the median eminence, which connects inferiorly with the pituitary stalk. Small arteries penetrate into the median
eminence and then additionalsmall vessels return to its surface, coalescing to form thehypothalamic-
hypophysial portal blood vessels. hormones into the tissue fluids.
