Microcirculation of the rat adrenal gland: a scanning electron microscope study of vascular casts.

Blood vascular beds of the rat adrenal gland were filled with methacrylate resin and observed with a scanning electron microscope. The classical findings on mammalian adrenal glands of Flint (1900), Bennett and Kilham (1940), and Gersh and Grollman (1941) were confirmed. The cortical capillaries arise from the cortical arteries and converge at the corticomedullary junction into the peripheral venous radicles which flow into the tributaries of the central vein. The medullary capillaries originate from the medullary arteries and drain through the deep venous radicles into the tributaries of the central vein. No direct connection between the cortical and medullary capillaries was noted except for rare communications via the peripheral venous radicles. These findings show that most of the cortical blood, rich in glucocorticoids, flows in the medulla, not through the medullary capillary plexus but exclusively through the radicles of the central vein. Evidence for adrenal portal vessels could not be found.