The kidneys are located in the posterior abdominal cavity and are protected by ribs and muscle. Each kidney has a bean shape with an indentation on the concave side called the renal hilus, where blood vessels and ureters enter and exit. Internally, the kidneys contain a cortex, medulla, minor and major calyces that collect urine, and a renal pelvis that drains urine into the ureter. Blood enters through renal arteries, is filtered through glomeruli in the cortex into tubules, and exits through renal veins back to the heart. The kidneys filter waste from the blood and are vital organs, as loss of both would lead to death within days from waste accumulation.