Could a doctor please explain about the renal circulation?

Real circulation.: oxygenated blood goes into kidney via renal arteries. These get progressively smaller until it becomes the afferent arteriole and enters into a a network in the renal glomerulus. This is where blood is filtered to remove wastes. The cleaned blood goes out of the glomerulus thru the efferent arteriole. Then into the veins. The circulation is controlled in part the the renin angiotensin system.