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Afferent Arteriole
- Small branch of interlobular renal artery, enters glomerulus on vascular pole.
- Brings arteriole into glomerulus.
- Branches into glomerular capillaries that form the efferent arteriole.
- Contains juxtaglomerular cells.
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Blood Supply
- Kidneys recieve 20-25% of CO
- 90% arterial blood stays in cortex
- 9% enters outer medulla
- 1% reaches the inner medulla.
- Kidney maintains constant blood flow by autoregulation that functions when perfusion pressure is 60-180 mmhg
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Glomerular Basement Membrane (GBM)
- Selectively permeable specialized vascular basement membrane outlining glomerular capillaries.
- Regulates ultrafiltration of plasma and formation of primary urinary filtrate.
- With fenestrated endothelial cells and foot processes forming epithelial cells (podocytes).
- GBM forms glomerular capillary wall
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Glomerular filtration rate (GFR)
- Rate at which the plasma is filtered in glomeruli, forming GUF.
- Renal plasma flow=600 ml/min and the ratio of renal plasma flow to GFR is constant at 5:1
- GFR ~120 ml/min
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Glomerulus
- Initial portion of nephron between afferent and efferent arterioles on one side and the proximal convoluted tubule on other.
- Made of fenestrated capillaries enclosed by Bowman's capsule
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Juxtaglomerular Apparatus
- Structure composed of specialized renin secreting cells localized in wall of afferent arteriole in glomerulus.
- Cells of macula densa a specialized part of distal convoluted tubule.
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Kidneys
- Paired organs in retroperitoneum
- Cortex outer part, medulla inner part.
- Main function=formation of urine and elimination of superfluous water and minerals, met. waste products, drugs.
- Secrete=hormones, growth factors, renin and epo
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Mesangium
- Connective tissue framework of glomerulus into glomerular tuft from vascular pole.
- Consists of mesangial cells and nonfibrillar ECM that fills space delimited by confluence of 3-4 glomerular capillaries.
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Nephron
- Basic functional unit comprising of glomerulus, PCT, loop of Henle, distal tubule, collecting ducts.
- connected to arterial blood supply and excretory urinary ducts.
- 2 types: cortical nephrons and juxtamedullary nephrons.
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Cortical Nephrons
- Short loops of henle
- surrouned by capillary networks
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Juxtamedullary nephrons
- long loops of henle extending into medulla.
- surrounded by vasa recta.
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Renal arteries
- There are two which originate from the abdominal aorta.
- Kidneys, they branch forming large interlobar arteries.
- give rise to arcuate arteries running along the corticomedullary junction.
- arcuate arteries give rise to cortical interlobar arteries, which give rise to afferent arterioles.
- Efferent arteriole leaving gives rise to peritubular capillaries and vasa rectus.
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Vasa Recta
drain into small renal veins.
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Renin
- Enzyme secreted by juxtaglomerular cells in response to reduced blood supply to kidney.
- acts on angiotensinogen, transforming to angiotensin, stimulating aldosterone production in adrenal cortex.
- Mechanism: renin raises the BP
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Ureter
Tubular organ serves as path for urine from renal pelvis to urinary bladder.
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Urethra
- Tubular organ serving as final path for fluid leaving urinary bladder during urination.
- Males: passageway for semen.
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Urinary Bladder
Hollow organ whose primary function is to store urine prior to urination.
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Urine
- Fluid formed in kidney from ultrafiltered plasma, containing in addition to water, minerals, organic waste material.
- Urine formed from nephron through a stepwise process that includes ultrafiltration of plasma, selective and site-specific reabsorption of minerals and water, secretion of other.
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Urothelium (Transitional epithelium)
Specialized epithelium lining the renal calices, pelvis, ureters, urinary bladder, and posterior part of urethra.
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Vitamin D
- Lipid-soluble vitamin hydroxylated in liver and after, the kidney.
- Active form of vitaimin, 1,25 formed.
- Regulates absorption and metabolism of calcium along with Parathyroid hormone.
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Anuria
- Absence of urine (<100 ml urine/day)
- Anuria is sign of renal failure and may be prerenal, intrarenal, postrenal.
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Prerenal
Due to reduced renal perfusion in heart failure.
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Intrarenal
Due to glomerulonephritis or toxic tubular necrosis
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Postrenal
Due to obstruction of ureters or bladder outflow tract.
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Azotemia
- increased blood concentration of N2-containing compounds (urea/creatinine).
- [blood] of urea is conventionally expressed as BUN.
- Sign of renal railure.
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Glycosuria
- Appearance of glucose in urine in excess of minimal amounts normally found in urine
- (<200 mg/24 hrs)
- Consequence of hyperglycemia
- Diatbetes mellitus
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Hematuria
- Blood in urine
- Macroscopic and visible to naked eye or microscopic and detectable only by microscopic examination of renal sediment.
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Lipiduria
- Appearances of lipid droplets or lipid casts in urine.
- Found in nephrotic syndrome and hyperlipemic states.
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Oliguria
- Production of urine in small amounts.
- Sign of renal failure, which may be prerenal, intrarenal, postrenal.
- Adults: <400 ml/day
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Polyuria
- Production of large quantities of urine.
- Increased frequency of urination, and an abnormally large volume of luid excreted over a 24 hr period.
- Adults: urine make exceeds 3-5 l/day
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Proteinuria
- Excretion of proteins in urine in excess of the normal amount for the age of the patient.
- Healthy: < 500 mg protein
- Sign of glomerular injury and occurs in nephritic and nephrotic syndromes.
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Pyuria
- Excretion of pus in urine.
- Caused: bacterial infection
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Urinary Casts
- Cylindrical structures found in urine, typically formed from protein-rich contents of the renal tubules.
- Granular Casts
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