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74 Cards in this Set
- Front
- Back
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What is the most important function of the kidney?
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maintain salt and water balance
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Where in the kidneys does filtration occur?
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glomeruli
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Where in the kidneys does reabsorption occur?
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tubules
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Where in the kidney does secretion occur?
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mostly in proximal tubule
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What are the endocrine secretions of the kidney?
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renin, erythropoietin, PGs, kinins
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What hormones are degraded in the kidney?
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PTH, insulin
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What are the parts of the kidney?
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glomerulus, proximal tubule, thin and thick loop of Henle, distal convoluted tubule, collecting duct
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How fast are things filtered in teh kdieny?
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1L/min
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What determines GFR?
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balance of hydrostatic and oncotic pressure
Kf[(Pgc - Pb) - (Ogc - Ob)] = GFR |
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What is typical GFR?
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120 mL/min
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What molecules are absorbed in the proximal tubule?
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65-70% water, Na, K
100% glucose, bicarb, amino acids, citrate, small peptides 40-50% Ca 80-90% PO4 |
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What is the osmoticity of absorption in the proximal tubule?
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isosmotic
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What is the absorbed early in the proximal tubule?
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sodium with, glucose, sulfate, phsophate, AAs, organic acids
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What mediates early transport in the proximal tubule?
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Na-coupled cotransporters
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What is absorbed late in the proximal tubule?
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Na with Cl
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What mediates late transport in the proximal tubule?
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Na/H exchanger
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How is bicarbonate reabsorbed in the proximal tubule?
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Na/H exchanger on luminal membrane and carbonic anhydrase enzyme in proximal tubule cell
for each H excreted, one HCO3- |
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What hormones act in the proximal tubule?
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angiotensin II, catecholamines, atrial natriuretic peptide, dopamine
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What does Angiotensin II do in the proximal tubule?
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stimulates reabsorption of Na and HCO3 by increasing activity of apical Na/H exchanger
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What do catecholamines do in the proximal tubule?
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stimulates reabsorption of Na and HCO3 by increasing activity of apical Na/H exchanger
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What does atrial natiuretic peptide do to the proximal tubule?
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blocks effects of angiotension II and catecholamines
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What does dopamine do to the proximal tubule?
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reduces Na reabsoprtion by inhibiting Na/K-ATPase
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What happens in acute tubular necrosis?
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damage of the tubule by aminoglycoside antibiotics, myoglobin, LPS from gram negative bacteria
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What is Fanconi syndrome?
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global dysfunction of proximal tubule with excessive urinary excretion of amino acids, glucose, phosphate, bicarbonate
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What are the results of Fanconi syndrome?
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acidosis dehydration, electrolyte imbalance, rickets, osteomalacia, growth failure
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What can cause Fanconi syndrome?
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inborn errors of metabolism, heavy metals, tetracycline, chemo, Chinese herbs
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What are the four parts of the loop of Henle?
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thin descending, thin ascending, medullary thick ascending limb, cortical thick ascending limb
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What does the thin descending limb absorb?
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water and urea through aquaporin 1, impermeable to Na
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What happens in the thin descending limb?
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isotonic fluid from proximal tuuble becomes more concentrated as it descends
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What happens in the thin descending limb?
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urinary dilution
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What does atrial natiuretic peptide do to the proximal tubule?
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blocks effects of angiotension II and catecholamines
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What does dopamine do to the proximal tubule?
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reduces Na reabsoprtion by inhibiting Na/K-ATPase
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What happens in acute tubular necrosis?
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damage of the tubule by aminoglycoside antibiotics, myoglobin, LPS from gram negative bacteria
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What is Fanconi syndrome?
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global dysfunction of proximal tubule with excessive urinary excretion of amino acids, glucose, phosphate, bicarbonate
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What are the results of Fanconi syndrome?
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acidosis dehydration, electrolyte imbalance, rickets, osteomalacia, growth failure
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What can cause Fanconi syndrome?
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inborn errors of metabolism, heavy metals, tetracycline, chemo, Chinese herbs
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What are the four parts of the loop of Henle?
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thin descending, thin ascending, medullary thick ascending limb, cortical thick ascending limb
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What does the thin descending limb absorb?
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water and urea through aquaporin 1, impermeable to Na
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What happens in the thin descending limb?
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isotonic fluid from proximal tuuble becomes more concentrated as it descends
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What happens in the thin descending limb?
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urinary dilution
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What is absorbed in the thin ascending limb?
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NaCl, impermeable to water
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What is reabsorbed in the thick ascending limb?
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25-30% of NaCl
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What drives reabsorption in the medullary thick ascending limb?
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Na/K-ATPase on basolateral membrane, Na/K/2Cl on luminal membrane
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What blocks the Na/K/2Cl transporter on luminal membrane of medullary thick ascending limb?
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loop diuretics
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What causes Bartter's Syndrome?
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mutation in Na/K/2Cl cotransporter
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What happens in Bartter's Syndrome?
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volume depletion, salt wasting, hypercalciuria, hypokalemic metabolic alkalosis
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What happens to K+ in the medullary thick ascending limb?
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refluxes back into tubular lumen through ROMK channels
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What does the ROMK channel do?
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ensures adequate K for cotransporter, net positive lumen potential for paracellular reabsorption of Na, K, Ca, Mg
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What is the net result of the medullary thick ascneding limb?
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hypertonic fluid enters, becomes more dilute with production of hypertonic medullary intersititum
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What is the fluid like in the cortical thick ascending limb?
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hypotonic, 100-120 mOsm/L
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What is absorbed in the distal convoluted tubule?
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NaCl, no water
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What drives transport in the distal convoluted tubule?
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Na/K-ATPase on basolateral membrane, Na/Cl symporter on luminal membrane
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What inhibits the Na/Cl symporter on luminal membrane of the distal convoluted tubule?
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thiazide diuretics
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What causes Gitelman's syndrome?
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mutation in Na/Cl symporter in distal convoluted tubule
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What happens in Gitelman's syndrome?
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volume depletion, salt wasting, hypocalciuria, hypomagnesemia
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How does PTH change the distal convoluted tubule?
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inserts Ca channels into apical membrane for reabsorption
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What are the two cells in the collecting duct?
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principal, intercalated
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What does the principal cell do?
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reabsorption of NaCl and water, secretion of K
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How is sodium transported in the principal cell?
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apical entry though epithelial sodium channels, basolateral Na/K-ATPase
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What blocks the epithelial sodium channels?
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amiloride and spironolactone
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What happens in Liddle's syndrome?
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enhanced reabsorption of Na due to constitutive overactivity of ENaC in collecting duct with hypertension and hypokalemia
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What does the intercalated cell do?
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secretion of H+
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What secretes aldosterone?
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zona glomerulosa of adrenal cortex
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What is the mechanism of aldosterone?
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stimulates number/activity of Na, K, channels, Na/K-ATPase and H-ATPase in collecting duct
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What is the result of aldosterone?
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increases Na reabsorption, acid secretion, K secretion in collecting duct
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What does ADH do?
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inserts aquaporins into apical membrane of collecting duct
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What does ADH do to the urine?
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concentrates it with hypertonic medullary interstitium
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What is the defect in the transporter in the proximal tubule?
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Fanconi syndrome
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What is the defect in transporter in the loop of henle?
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Bartter's syndrome
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What is the defect in the transporter in the distal convoluted tubule?
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Gitelman's syndrome
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What is glomerulotubular balance?
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extent of sodium reabsorption in a given nephron segment is proportional to sodium delivery of that segment
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How is glomerulotubular balance not perfect?
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doesn't reabsorb exactly as much as the increase in Na, so additive effects, lose more Na in the urine as it goes through the tubule
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What is the countercurrent multiplication system?
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generates energy-efficient means for NaCl to be deposited
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What happens in the countercurrent multiplication system?
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NaCl reabsorbed from thick ascending limb, hypertonic interstitium stimulates water reabsorption from thin descending limb, creates hypertonic fluid in thin descending limb, more isotonic fluid enters from proximal tubule, hypertonic fluid delivered to ascending limb
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