Kidney ‒ Section

**Structure of the Kidney**

Externally, the kidneys are encased by three layers. The outermost layer, called the renal fascia, is a tough connective tissue. The second layer, the perirenal fat capsule, helps anchor the kidneys in place. The innermost layer is the renal capsule. Internally, the kidney has three main regions: the outer cortex, the medulla in the middle, and the renal pelvis in the area known as the hilum. The hilum is the concave part of the kidney where blood vessels, nerves, and the ureter enter and exit. The renal cortex has a granular appearance due to the presence of nephrons, which are the functional units of the kidney. The medulla contains multiple pyramid-shaped tissue masses called renal pyramids, with an average of eight per kidney. Renal columns are spaces between these pyramids, allowing blood vessels to pass through. The tips of the pyramids, known as renal papillae, point toward the renal pelvis. Each renal pyramid and its surrounding cortical tissue make up a kidney lobe. The renal pelvis connects to the ureter outside the kidney. Inside, the renal pelvis branches into two or three major calyces, which further divide into minor calyces. The ureters, which carry urine from the kidneys, then empty into the urinary bladder.



*LICENSES AND ATTRIBUTIONS

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