The majority of nephrons in the kidney are cortical nephrons, located in the renal cortex. Only 15 percent of nephrons are juxtamedullary nephrons, which are located in the area of the kidney where the cortex and medulla meet, according to Midlands Technical College. Cortical nephrons have short nephron loops, while juxtamedullary nephrons have long nephron loops. The long nephron loops in the juxtamedullary nephrons produce the osmotic gradient that regulates urine concentration.
Both cortical and juxtamedullary nephrons filter the blood and process waste products into urine, explains Healthpages. Each kidney has about one million nephrons that clean waste products from the blood in three steps. Clusters of capillaries in the nephron called glomeruli first filter the blood by a process called glomerular filtration.
Filtered blood then passes into the tubules of the cortical and juxtamedullary nephrons where organic nutrients, water and ions are regulated and reabsorbed, reports Healthpages. It flows into the short cortical nephron loops and long juxtamedullary nephron loops where water, electrolytes, calcium and magnesium are removed from the filtrate. The last stage, tubular secretion, eliminates solutes and excess potassium and regulates blood pH as the filtrate passes into the collecting ducts and then the bladder, explains Midlands Technical College.