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The kidney is surrounded by tough fibrous tissue, the renal capsule, which is itself surrounded by perirenal fat, renal fascia, and pararenal fat. The anterior (front) surface of these tissues is the peritoneum, while the posterior (rear) surface is the transversalis fascia. The superior pole of the right kidney is adjacent to the liver.
The renal calyces (sg. calyx) are conduits in the kidney through which urine passes. The minor calyces form a cup-shaped drain around the apex of the renal pyramids.Urine formed in the kidney passes through a renal papilla at the apex into the minor calyx; four or five minor calyces converge to form a major calyx through which urine passes into the renal pelvis (which in turn drains urine out ...
From anterior to posterior, the renal vein exits, the renal artery enters, and the renal pelvis exits the kidney. On the left hand side the hilum is located at the L1 vertebral level and the right kidney at level L1-2. The lower border of the kidneys is usually alongside L3.
[citation needed] A large "staghorn" kidney stone may block all or part of the renal pelvis. The size of the renal pelvis plays a major role in the grading of hydronephrosis . Normally, the anteroposterior diameter of the renal pelvis is less than 4 mm in fetuses up to 32 weeks of gestational age and 7 mm afterwards. [ 2 ]
The renal sinus is a cavity within the kidney which is occupied by the renal pelvis, renal calyces, blood vessels, nerves and fat.The renal hilum extends into a large cavity within the kidney occupied by the renal vessels, minor renal calyces, major renal calyces, renal pelvis and some adipose tissue.
Despite their relatively small size, the kidneys receive approximately 20% of the cardiac output. [ 1 ] Each renal artery branches into segmental arteries, dividing further into interlobar arteries , which penetrate the renal capsule and extend through the renal columns between the renal pyramids.
Mammalian kidneys are susceptible to ischemic injury because mammals lack a renal-portal system, and as a result, vascular vasoconstriction in the glomeruli can lead to decreased blood supply to the entire kidney. The kidneys are susceptible to toxic injury, since toxins are reabsorbed in the tubules along with most of the filtered substances. [47]
The renal lobe is a portion of a kidney consisting of a renal pyramid and the renal cortex above it. [1] In humans, on average there are 7 to 18 renal lobes. [medical citation needed] It is visible without a microscope, though it is easier to see in humans than in other animals.