Renal microcirculation of the bullfrog, Rana catesbeiana. A scanning electron microscope study of vascular casts

The microcirculation of the bullfrog kidney was studied by scanning electron microscopy of the corrosion casts. The bullfrog kidney derives its blood supply from a dual origin: one is from the posterior half of the body via the renal portal veins and the dorso-lumbar veins, the other is from the urogenital arteries. The renal portal veins are linked with the hepatic portal system through the anterior abdominal vein which might serve as a transport route of the potentially renal portal blood to the kidney. The glomerulus consists of several lobules of anastomosing capillaries which are intercalated between the afferent and efferent arteriole. The efferent arteriole of the glomerulus runs some distance ventrad without branching to join the peritubular sinusoidal capillaries near the ventral surface of the kidney. Usually each glomerulus has a single efferent arteriole, but double efferent arterioles may rarely occur. Near the medial border of the kidney the glomeruli are small, and laterally they become progressively larger.