Nephrology In humans, the kidneys are bean-shaped organs about four inches long, found in the body near the spine, excreting waste products of metabolism and consisting mainly of nephrons from which urine is secreted, collected, and discharged. to the pelvis of the kidney, from where it is transported through the ureter to the bladder, controls red blood cell production, produces an active form of vitamin D, which strengthens and heals bones, and removes waste products and medicines...