Kidney: Cortex, medulla and pelvis

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The kidneys are paired retroperitoneal organs of the urinary system. Their function is to filter blood and produce urine. Each kidney consists of a cortex, medulla and pelvis.

• The renal cortex is the outer layer of the kidney tissue and contains ovoid and coiled parts of the nephrons (renal corpuscles and convoluted tubules).

• The renal medulla consists of renal pyramids separated by the renal columns. The apices of the pyramids project towards the renal pelvis and open into the minor calyces via perforated plates on their surfaces (area cribrosa). Each renal pyramid, with its surrounding cortical tissue, forms a renal lobe. Renal lobes are further divided into renal lobules. Each lobule consists of a group of nephrons emptying into one collecting duct.
• The renal pelvis consists of the minor and major calices which are lined by transitional epithelium (urothelium) supported by a lamina propria and smooth muscle layers. This system collects urine from the renal papillae and facilitates its transport to the ureter.

Watch the following video to learn more about the histological appearance of the kidney. (Note: this video also covers material related to the next study unit, Kidney: Nephron and juxtaglomerular apparatus.)

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Kidney