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Structure and Function of the Renal and Urologic SystemsChapter 35

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Structures of the KidneyKidneys

RetroperitonealRenal capsuleRenal fasciaHilum

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Structures of the Kidney

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Structures of the KidneyRenal cortexRenal medullaRenal pyramidsRenal columnsMinor calyx Major calyxRenal pelvis

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Structures of the Kidney

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Nephron1.2 million nephrons per kidney Functional unit of the kidney

Superficial cortical nephronsMidcortical nephronsJuxtamedullary nephrons

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NephronRenal corpuscle

GlomerulusBowman capsuleMesangial cells

Bowman space

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NephronGlomerular filtration membrane

Glomerular endotheliumBasement membraneCapillary epithelium

Also referred to as podocytes or visceral epitheliumFiltration slits

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NephronJuxtaglomerular apparatus

Juxtaglomerular cellsMacula densa

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Juxtaglomerular Apparatus

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NephronRenal tubules

Proximal tubuleLoop of HenleDistal tubuleCollecting ductPrincipal cellsIntercalated cells

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Structures of the Kidney

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Structures of the Kidney

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Blood VesselsRenal arteriesInterlobar arteriesArcuate arteriesInterlobular arteriesAfferent arteriolesGlomerular capillariesEfferent arteriolesPeritubular capillaries and vasa recta

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Structures of the Kidney

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Structures of the KidneyUreters

30 cm longLong, intertwining muscle bundlesPass obliquely though posterior aspect of bladderPeristaltic activityMicturition compresses the lower end of the ureter to avoid urine reflux

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Structures of the KidneyBladder

Detrusor muscleTransitional epitheliumTrigoneMicturition reflex

UrethraInternal and external sphincters3 to 4 cm in females18 to 20 cm in males

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Bladder and Urethra

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Renal Blood FlowReceive 1000 to 1200 mL of blood per minuteGlomerular filtration rate (GFR)Autoregulation

Myogenic mechanismTubuloglomerular feedback

Neural regulationHormones

Renin-angiotensin systemNatriuretic peptides

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Renal Blood Flow

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Nephron FunctionGlomerular filtration

Net filtration pressureGlomerular hydrostatic pressureCapsular hydrostatic pressureBlood oncotic pressure

Filtration rate

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Glomerular Filtration

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Nephron FunctionTubular reabsorptionTubular secretionExcretionTubular transport

Proximal tubuleLoop of Henle and distal tubuleGlomerulotubular balance

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Nephron Function

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Nephron Function

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Nephron Function

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Concentration and Dilution of Urine

Countercurrent exchange systemContributes to production of concentrated urineFluid flows in opposite direction through parallel tubesFluid moves up and down the parallel limbs of the loop of HenleThe longer the loop, the greater the concentration gradient

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Countercurrent Exchange System

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Concentration and Dilution of Urine

UreaCatecholaminesAntidiuretic hormone (ADH)UrodilantinNatriuretic peptideDiuretics

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Renal HormonesVitamin DErythropoietin

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Tests of Renal FunctionClearance and glomerular filtration rate

InulinCreatinine

Clearance and renal blood flowBlood tests

Plasma creatinine concentrationPlasma cystatin C concentrationBlood urea nitrogen (BUN)

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Tests of Renal FunctionUrinalysis

Urine colorUrine pHSpecific gravityUrine sediment

RBCsCastsCrystalsWBCs

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Tests of Renal FunctionUrinalysis

Reagent strips (dipsticks)GlucoseBilirubinUrobilinogenLeukocyte esteraseNitratesKetonesProteinsRBCs, hemoglobin, and myoglobin

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Aging and Renal FunctionDecrease in kidney sizeDecrease in renal blood flow and GFRNumber of nephrons decrease due to renal vascular and perfusion changesGlomerular capillaries atrophyTubular transport response decreasesIncreased bladder symptoms

Urgency, frequency, and nocturia