Two types of nephrons that exists are the cortical nephrons and the juxtamedullary nephrons. The nephron is the functional unit of the kidney. Approximately one million nephrons are present in each human kidney.
Nephrons vary in complexity based on the organism. The most primitive nephrons are found in embryos of advanced vertebrates, primitive fish and amphibian larvae. More advanced vertebrates and most fish have nephrons that are slightly more complex. The most complex nephrons exist in the adult kidneys of mammals, reptiles and birds. Each nephron of the mammalian kidney consists of a renal corpuscle surrounded by a glomerular capsule and a renal tubule.