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66 Cards in this Set
- Front
- Back
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What are the 7 functions of the kidneys? |
-Excretion of metabolic waste products and foreignchemicals -Regulation of water and electrolyte balances -Regulation of body fluid osmolality and electrolyteconcentrations -Regulation of arterial pressure -Regulation of acid-base balance -Secretion,metabolism, and excretion of hormones -Gluconeogenesis |
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- name 4 metabolites which are excreted in the kidneys and state where they originate from |
- urea: metabolism of amono acids - creatinine: from muscle creatine - uric acid: from nucleic acid breakdown - bilirubin: haemaglobin catabolisation |
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Where is eryhthropoietin produced and what is the stimulus for its production |
- kidneys - hypoxia |
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From deep to superficial, what are the three layers which surround the kidney? |
- deep: renal capsule - intermediate: adipose tissue - superficial: renal fascia |
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What 2 structures in the kidneys constitute the parenchyma? |
- renal cortex and renal pyramids |
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Describe the path of filtrate/urine and is leaves the nephron (7) |
- colecting duct - paillary duct - minor calyx - major calyx - renal pelvis - ureter - urinary bladder |
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How much of the cardiac output do the kidnes receive? |
- 20-25% |
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Describe the passage of blood flow in and out of the kidneys (13) |
- renal artery - segmental artery - interlobar arteries - acuate arteries - intelobular arteries - afferent arterioles - glomerular capillaries - efferent arterioles - peritubuar capillaries - interlobular veins - arcuate veins - interlobar veins - renal vein |
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What 2 structures make up the renal corpuscle? What are the 2 types of nephron? What is the percentage of each? |
- Bowman's capsule and glomerulus - cortical and juxtamedullary - 80-85% cortical; 15-20% juxtamedullary |
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List 5 differences between cortical and juxtemedullary nephrons |
- corticalnephrons have their renal corpuscle closer to the exterior of therenal cortex - cortical nephrons haveshort loops which only marginally protrude into the medulla - cortical nephrons are supplied by the peritubular capilaries, juxtamedullary nephrons are supplied peritubular capillaries and the vasa recta - juxtamedullary nephrons have thick and thin ascending limbs - juxtamedullary nephrons produce concentrated urine |
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What are the 2 layers of the glomerular capsule? Describe the structure of each |
- visceral and parietal - visceral is composed ofpodocytes - a modified form ofsimple squamous epithelium - parietal layer issimple squamous epithelium |
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What epithelial cells line; PCT descending and thin ascending limb thick ascending limb DCT and collecting duct |
PCT: simple cuboidal with microvilli descending and thin ascending limb: simple squamous thick ascending limb: simple cuboidal to low columnar DCT and collecting duct: simple cuboidal |
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Other than epithelial cells, what cells would you find in the DCT and collecting duct? |
- principal and intercalated cells |
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What are the 3 main functions of nephrons responsible for maintaining homeostasis |
- glomerular filtration, tubular secretion and tubular reabsorption |
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What are the 3 layers of the filtration membrane? |
- glomerular endothelial cells - basal lamina - slit membrane |
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Describe the structure and function of the glomerular endothelial cells which form part of the filtration membrane (3) |
- Containlarge fenestrations - allowsa large portion of plasma components through. Does not allow bloodcells and platelets. - Mesangialcells can be found just before entry to the capsule – regulatingrenal blood flow. |
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Describe the structure and function of the basal lamina which forms part of the filtration membrane (2) |
- collagenand proteoglycans in a glycoprotein matrix. - Posses a negative chargewhich prevents the filtration of larger, negatively charged proteins. |
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Describe the structure and function of the slit membrane which forms part of the filtration membrane (3) |
- essentially,gaps in the pedicles. - Gaps are covered by a thin membrane whichallows the passage of medium-sized proteins – e.g. water, glucose,vitamins, amino acids, small plasma proteins, ammonia, urea and ions.Small amount of albumin will pass through (<1%). |
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What 3 factors facilitate the large amount of filtration that occurs through the glomerular capilaries |
(1) Glomerualrcapillaries have a large surface area. This surface area is increasedby the relaxation of mesangial cells and vice versa. (2) collectively, thefiltration membrane is both thin and porous and, due to theirfenestrations, much leakier than normal capillaries (3) glomerular capillaryblood pressure is high because the afferent arteriole is larger thanthe efferent arteriole |
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What are the 3 types of pressure which influence filtration through the filtration membrane? State whether they are negative of positive forces. |
POSITIVE: GlomerularBlood Hydrostatic Pressure (GBHP) - pressure in the glomerularcapillaries (~55mmHg) NEGATIVE:CapsularHydrostatic Pressure (CHP) – pressure exerted by fluid already inthe capsular space and tubules NEGATIVE: Blood ColloidOsmotic Pressure (BCOP) – presence of proteins in the blood plasmae.g. albumin, globulins |
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Define GFR What are the 2 broad mechanisms by which GFR is regulated? |
- GFR: the amount offiltrate formed in all renal corpuscles in both kidneys each minute(~125ml/min/105ml/min) - (1) adjusting blood flowinto the glomerulus, and (2) altering the surface area of theglomerular capillaries to change increase/decrease filtrate |
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Describe renal autoregulation of GFR (4) |
- worksto maintain a constant GFR despite a changing environment - uses two mechanisms:myogenic mechanism and tubuloglomerular feedback - in the myogenicmechanims, an increase in BP activates stretch receptors in theafferent arterioles, causing them to contract and reduce GFR - in tubuloglomerularfeedback, cells in renal tubules called macula densa - which surroundthe inside of the tubules – detect the amount of Na and Cl. As theamount of these ions will be at least partially determined by flow,these cells can help to control the amount of NO which is released –influencing vasodilation and vasoconstriction. |
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Describe neural regulation of GFR (4) |
- renal blood vessels areinnervated by sympathetic nerves of the autonomic nervous systemwhich release noradrenaline. - noradrenaline causesvasoconstriction by acting on alpha-1 receptors which are abundant insmooth muscle in afferent arterioles - an increase insympathetic stimulation, such as occurs during exercise, causes theafferent (and efferent) arterioles to constrict, reducing the flowinto the glomerular capillaries - this has two effects:(1) reduces urine output and (2) means more blood flows other tissues |
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Describe hormonal regulation of GFR (4) |
- angiotensin II reducesGFR; atrial natriuretic peptide increases GFR - angiotensin II acts asa potent vasoconstrictor on efferent and afferent capillaries –reducing blood flow and GFR - atrial natriureticpeptide is released from the atria when it becomes stretched. ANPacts on mesangial cells – contractile cells in the first layer ofthe filtration membrane – causing them to relax. - relaxation of themesangial cells causes the capillaries to increase in size –increasing their surface area and increasing GFR |
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How are small proteins and peptides generally reabsorbed? |
- pinocytosis |
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Describe the main symporter in the PCT Describe the main antiporter in the PCT What type of water channels are present in the PCT? |
- (2x)sodium-glucose symporter in the apical membrane - sodium/hydrogenantiporter. It moves sodium from the tubular fluid into the tubulecell of the proximal convoluted tubule, in exchange for hydrogen - aquaporin 1 |
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What is the main channel present in the thick ascending limb? What perecentage of water is reabsorbed in the DCT? |
- sodium-potassium-(2x)chloridesymporters - 10-15% |
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What is the function of principal cells? How do they do it? What is the function of intercalated cells? How do they do it? |
- fluid regulation: reabsorb sodium andsecrete potassium in response to ADH and aldosterone - regulate pH: reabsorb potassium andsecrete bicarbonate (HCO3-) |
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Describe the renin-angiotensin-aldosterone system (essay answer) |
- when blood flow intothe afferent arterioles is reduced, the pressure on the walls isdecreased. This causes sympathetic stimulation and the secretion ofrenin from the juxtaglomerular cells – cells surrounding thearterioles. - renin convertsangiotensinogen from hepatocytes into angiotensin I - angiotensin I isconverted to angiotensin II by Angiotensin-Converting Enzyme (ACE) - Angiotensin II hasthree functions;(1) causesvasoconstriction of the afferent arterioles reducing GFR (decreasereabsorption, retain fluid)(2) Stimulates activityof Na/H antiporters in the proximal convoluted tubule, increasingreabsorption of Na and Cl(3) stimulates therelease of aldosterone from the adrenal cortex, which stimulatesprincipal cells in the collecting ducts to reabsorb Na and Cl, andsecrete K. The net result of this is water absorption due to osmosis. |
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Where is ADH produced? Where does it act? What does it do (3)? |
- posterior pituitary - principal cells in the DCT and collecting duct - (1) regulates facultativewater reabsorption bi increasing the permeability of principal cells (2) stimulates theinsertion of aquaporin- 2 channels, (3) causes water toflow more rapidly into the cells and through the basolateral membrane |
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Describe the function of atrial natriuretic peptide (3)? |
- inhibits reabsorptionof sodium and water in the distal convoluted tubule and collectingduct - suppresses secretion ofaldosterone and ADH - overall effect is lossof Na and increased urine output |
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Describe the function of parathyroid hormone (3) |
- reduced calcium in theblood stimulates the release of parathyroid hormone from theparathyroid glands - stimulates cells in theearly distal convoluted tubule to reabsorb more calcium into theblood - also promotes theexcretion of phosphates |
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Describe the formation of dilute urine (essay anwer) |
- as tubular fluid movesdown the descending limb, water is drawn out of the tubule by osmosisdue to the increasing osmolarity of the interstitial fluid. Thismeans the solute concentration in the lumen becomes greater. - in the thick ascendinglimb, sodium, potassium and chloride are reabsorbed due tosymporters. However, this portion of the tubule is relativelyimpermeable to water, so water cannot follow. This reduce theosmolarity in the tubule. - in the distalconvoluted tubule, additional solutes are lost but few watermolecules - principal cells in thelate distal convoluted tubule are impermeable to water, furtherpreventing reabsorption of water |
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What 2 mechanisms contirubte to the formation of concentrated urine? |
- countercurrent multiplication and countercurrent exchange |
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Describe countercurrent multiplication (essay answer) |
- due tosodium-potassium-(2x)chloride symporters in the thick ascending limb,and the fact that tubules here are impermeable to water, there is abuild up of solutes and ions in the interstitial fluid of themedulla. It is this build up of ions which produces the gradient inthe medulla – about 300 milliosmoles/L higher up in the medulla,and about 1200 milliosmiles/L deeper in the medulla. - the descending limb ispermeable to water but relatively impermeable to solutes – excepturea. As such, water is increasingly reabsorbed as it moves down thedescending tubule, due to the osmotic gradient produced by the thickascending limb. This makes the inside of the tubule increasinglyconcentrated. - the collecting duct(and distal convoluted tubule) have receptors for antidiuretichormone. ADH increases the permeability of the tubules here, causingwater to leave the tubules through osmosis. As the water leaves, theconcentration of urea increases. However, the cell in the ducts arepermeable to urea, so they also become reabsorbed. - the build up urea inthe interstitial fluid causes some of it to diffuse into thedescending and thin ascending limb. The urea remains in the lumen asit cannot diffuse through the cells of the thick ascending limb,distal convoluted tubule and cortical portion of the collection duct– UNTIL it gets to the more distal regions of the collection duct. - the above means thaturea is constantly being recycled and contributing to the osmoticgradient in the medulla. By changing the amount of water which isable to be absorbed by using ADH, increasing amounts of water areable to leave the tubules – producing increasingly concentratedurine as it moves down the collection duct. |
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What is the purpse of countercurrent exchange? |
- maintains the gradient in the renal medulla |
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Describe countercurrent exchange (essay answer) |
- the vasa recta followsthe same position as the descending and ascending limbs of Henle - in the descending limbwater is increasingly lost from the vasa recta due to the increasingsolute concentration in the medulla. On it's own, this would destroythe gradient which the nephrons rely on. - However, as the blood flowsback up throught the ascendng limb of the vasa recta, the osmolarityof the medulla decreases. - As such, solutes and ions flow back in tothe medulla from the vasa recta – more or less addressing thebalance while still performing gas exchange. |
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Name 3 kidney function tests |
- serum creatinine - blood urea nitrogen - cystatin C |
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What is serum creatinine derived from? What is blood urea nitrogen derived from? |
- waste product of muscles - nitrogenous end-productof amino acid and protein breakdown |
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What are the normal values for serum creatinine? What isthe normal value for BUN? |
- 110-150ml/min (men) and100-130ml/min (women) - >90 |
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Why is creatinine phosphate a poor measure of kidney function (7)? Name 3 conditions serum creatinine would be elevated other than kidney disease |
- influenced by musclemass and muscle function of a person, muscle composition, activity,diet, general health, age race and body size - muscular dystrophyparalysis, anaemia, leukaemia and hyperthyroidism |
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Why is BUN a poor indicator of renal function (3) Name 6 conditions where BUN would be elevated other than renal disease |
- influenced by non renalfactors (e.g. diet and urea cycle enzymes) - associated with kidneydisease or failure, blockage of the urinary tract by kidney stones,congestive heart failure, dehydration, fever, shock, GI bleeding, pregnancy and high protein foods |
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What value of BUN is suggestive of severe kidney disease? Name 5 situations where BUN would be reduced? |
- >100mg/dl - fluid excess, trauma,surgery, opiods, malnutrition and anabolic steroid use |
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Name 3 conditions proteinuria is an independent risk factor for How is proteinuria best measured? |
- CVD, death and end stagerenal disease - protein-creatinine ratio |
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Name 4 ions that would be measured in a electrolyte panel Which ion is most significant in assessing renal failure? |
- sodium, potassium,chloride, and bicarbonate - potassium |
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List 10 criteria which must be met in order to a liver donor to donate a kidney |
- donors need to make ainformed choice without coercion or monetary incentive - donors need to be givena cooling off period - donor needs to be ableto undergo general anaesthesia - needs to be medicallycapable of living with one kidney - no active malignancy - chronic infection - no nephrolithisis due to a metabolic condition - controlled hypertension - overt proteinuria,glomerular pathology, or inadequate GFR - no sickle cell disease |
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List 7 additional factors which should be considered/assessed |
- HLA matching and blood group - age - obesity - diabetes - proteinuria - non-visible haematuria - pyuria - haematological disease |
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What are the three regions in kidney where a calcuili is most likely to form? |
- minor calyx - major calyx - renal pelvis |
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Which gender is most likely to get kidney stones and what age group? |
- men - 20-30 years |
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Name 3 inborn errors of metabolism associated with the formation of calculi? |
- gout - cystinuria - primary hyperoxaluria |
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Distinguish between hydronephritis and pyelonephritis |
- hydronephritis: swellingof a kidney due to occlusion and backup of urine - pyelonephritis: swelling of the kidney due to bacterial infection |
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What is the most likely symptom associated with a stone entering the ureter? |
- intenseflank pain (renal colic:“attackof acute abdominal pain localized in a hollow organ and often causedby spasm, obstruction, or twisting”). |
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What are the 2 most common ways of removing stones |
- lithiotripsy and endoscopy |
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What are the 4 main types of stones? |
- calcium stones - struvite/magnesium ammonium phosphate - uric acid stones - cystine stones |
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In order, from most to least, how common are each of these stones? |
-calcium stones are most common (~70%) - followed by infection stones(~15%) - followed by uric acid stones (5-10% - followed by cystinestones (1-2%) |
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What is the most likley finding in blood and urine of someone with calcium stones |
- hypercalcaemia(elevated blood calcium) and hypercalciuria (elevated urine calcium) |
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Name 3 conditions associated hypercalcaemia and hypercalciuria |
-hyperparathyroidism:abnormallyhigh concentration of parathyroid hormone in the blood, resulting inweakening of the bones through loss of calcium. -diffuse bone disease -sarcoidosis: attributed to nephrocalcinosis: “increased renalcalcium resulting in diffuse,fine, renal parenchymal calcification on radiology |
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How could the intestines be involved in the formation of calcium crystals? |
- hyperabsorption of calcium |
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How is hypocitrauria implicated in the formation of calcium stones? |
- citrate is protective - hypercitrauria (low citrate levels in the urine) may precipitatecalcium stones due to acidosis and chronic diarrhoea |
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How are magnesium ammonium phosphate stones formed? |
- infective stones -typically formed after infection with bacteria which convert urea toammonia - alkalineurine precipitates the formation magnesium ammonium phosphate salts |
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Name 2 genera of bacteria which are associated with magnesiumammonium phosphate? What are the name of the stones they can form? |
- Proteusspp. and some Staphylococci - staghorn calculi |
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How are uric acid stones formed? |
-common in patients with hyperuricaemia (elevated blood uric acid) –e.g. gout – and conditions involved in a high cell turnover –e.g. leukaemia -many patients, however (more than half) have neither hyperuircaemianor an increased amount of uric acid in their urine. It is thoughthat uric acid stones in these patients is due to an unexplainedtendency to excrete urine with a pH of lower than 5.5 – causingstones to form because uric acid is insoluble at lower pHs. |
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How do cystine stones form? |
-caused by genetic defects where cystine is not sufficientlyreabsorbed in the renal tubules - resulting in cystinuria -cystine is the least soluble amino acid and is therefore prone toprecipitating |
