THE VASCULARIZATION OF THE PITUITARY-GLAND OF THE CHICKEN (GALLUS-DOMESTICUS) - A SCANNING ELECTRON-MICROSCOPE STUDY OF VASCULAR CORROSION CASTS

Microvascular corrosion casts of the pituitary gland of one to nine-da y-old chickens (Gallus domesticus, white leghorn hybrids) were analyse d with the scanning electron microscope. Results show that the chicken median eminence is supplied by branches of the infundibular and the n eural-lobe arteries. They form a Bat two-dimensional primary capillary plexus, which lacks any capillary loops and is continuous with the pl exus in the neural lobe. The capillaries occupy about 60% of the total area of the median eminence. A subependymal plexus is present, showin g no contact with the plexus of the median eminence. The chicken neura l lobe consists of many hollow buds. These buds are supplied by branch es of the neural-lobe artery, which gives rise to a two-dimensional ca pillary meshwork similar to that of the median eminence. An anterior g roup of portal vessels, comprising 14-16 vessels with a mean diameter of 37 mu m, and a posterior group of portal vessels, comprising 2-4 sh orter and slightly thinner vessels, arise from the median eminence are the sole blood supply for the adenohypophysis (distal lobe). Anterior portal vessels supply the cephalic lobe and the most rostral area of the caudal lobe, and posterior portal vessels supply the caudal lobe o f the distal lobe. There are no short portal vessels connecting the ne ural lobe with the distal lobe. The (sinusoidal) capillary bed of the distal lobe is laminated. The chicken hypophysis drains into the caver nous sinus, which empties into the cerebral carotid veins. Within the period studied (days 1-9 after hatching) no age-related changes were f ound.