Anatomy of the Kidney and the Urinary System

The body has two kidneys, which belong to the human urinary system. The kidneys are bean-shaped organs, each about the size of your fist and weigh only about 160 grams each. They are located near the middle of your back, just below the rib cage. Figure 1 shows the main components of the urinary system.

Figure 1: Location of the kidneys

Anatomy of the Kidney and the Urinary System

Figure 2 shows a cut-away view of a kidney. Here you can see the different parts of the organ. Blood enters the kidney via the renal artery and leaves via the renal vein. In the cortex of the kidney there are approximately one million nephrons. In these nephrons, blood is filtered and urine is generated. The urine then travels to the pelvis of the kidney through tubules, which converge in so-called collecting tubules. The collecting tubules are situated in the medulla of the kidney. They open out into calices which unite to the pelvis of the kidney. From the pelvis, the urine flows through the ureter to the urinary bladder.

Figure 2: Cut-away view of a kidney

Content last updated
  1. Thews G, Mutschler E, Vaupel P: Anatomie, Physiologie, Pathophysiologie des Menschen. Wissenschaftliche Verlagsges. 2007.
  2. National Kidney Foundation (last visited 30.03.2010)

Did you know...?

  • The kidneys produce erythropoietin and active vitamin D.

  • The number of nephrons in your kidneys correlates with your birth weight.

  • 99 % of the primary urine filtered through the glomerular capillaries are reabsorbed in the tubules.

  • When the GFR of the kidneys is reduced at 50 %, the concentration of creatinine in blood will double.