Kidney ‒ Section

**Kidney Structure**



Externally, the kidneys are surrounded by three layers. The outermost layer is a tough connective tissue layer called the renal fascia. The second layer is called the perirenal fat capsule, which helps anchor the kidneys in place. The third and innermost layer is the renal capsule. Internally, the kidney has three regions ‒ an outer cortex, a medulla in the middle, and the renal pelvis in the region called the hilum of the kidney. The hilum is the concave part of the bean-shape where blood vessels and nerves enter and exit the kidney; it is also the point of exit for the ureters. The renal cortex is granular due to the presence of nephrons ‒ the functional unit of the kidney. The medulla consists of multiple pyramidal tissue masses, called the renal pyramids, which are on evarage eight in each kidney. In between the pyramids are spaces called renal columns through which the blood vessels pass. The tips of the pyramids, called renal papillae, point toward the renal pelvis. The renal pyramids along with the adjoining cortical region are called the lobes of the kidney. The renal pelvis leads to the ureter on the outside of the kidney. On the inside of the kidney, the renal pelvis branches out into two or three extensions called the major calyces, which further branch into the minor calyces. The ureters are urine-bearing tubes that exit the kidney and empty into the urinary bladder.



*LICENSES AND ATTRIBUTIONS

CC licensed content, Shared previously, The Kidneys and Osmoregulatory Organs, Authored by: OpenStax College. License: CC BY: Attribution. License Terms: Download for free at http://cnx.org/contents/PixBa--0@7/The-Kidneys-and-Osmoregulatory*

## Keywords
section of kidney cortex medulla artery vein renal pelvis ureter