The kidneys are located just above the pelvis on either side of the body. Each kidney is connected to the bladder by a ureter. The kidney receives blood from the renal artery while the renal vein carries blood from the kidneys back to the heart. In cross section you see that the kidney is composed of an outer region called the renal cortex and an inner region called the renal medulla. Furthermore, the kidney consists of repeating segments called renal pyramids. Within each renal pyramid there are numerous nephrons (the functional unit of the kidney). Fluid (urine) from the collecting ducts of nephrons within any given renal pyramid drains into a minor calyx. The urine then flows into the central region of the kidney (the renal pelvis) before entering the ureter which drains urine from the kidney to the bladder. The functional unit of the kidney is the nephron.