Gross Anatomy of the Kidneys
The kidneys in all the mammalian species are located retroperitoneally and essentially in a sublumbar position but may extend beneath the last ribs. The right kidney is slightly more cranial than the left and usually fixed into a depression in the liver; the left kidney is more mobile and pendulous.
The sublumbar fascia surrounding the kidneys are often well-filled with fat.Each kidney has an indentation on its medial aspect; this is the renal sinus and is the location for the renal vessels and nerves as they enter the kidney at the renal hilus. This is also the exit of the ureter from its dilated origin, the renal pelvis. The kidney is enclosed in a fibrous capsule that protects the inner parenchyma.
The renal parenchyma is divided into an inner medulla and an outer cortex. The cortex contains mainly the renal corpuscles and the convoluted portions of the tubules. The striated appearance of the medulla is due to the presence of very many collecting ducts. The medulla is divided into six to eight renal pyramids in the dog; these are cone-shaped with the widest dimension adjacent to the cortex and the apex, or renal papilla, directed towards the renal pelvis. At the corticomedullary junction the arcuate arteries are located curving over the bases of the pyramids to give origin to the interlobar arteries.
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