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33 Cards in this Set
- Front
- Back
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how much of the plasma crosses the filtration barrier?
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20%
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what mutations cause familial glucosuria?
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mutation in the glucose/Na symporter, SLGT2
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what blood/urine tests would be found in familial glucosuria?
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normal blood glucose
high urine glucose levels |
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what problem in the kidney can cause gout?
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too much reabsorption or too little secretion of urate/uric acid
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what is type 2 renal acidosis
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impaired ability to reabsorb bicarbonate
often occurs in chidlren as part of Fanconi's syndrome |
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what is normal GFR
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120ml/min
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what is normal RPF
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600ml/min
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what is PCV?
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0.4
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what is normal renal blood flow?
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1l/min
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what is normal caridac output?
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5.0 litres per minute
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what forces contribute to reabsorption of substances across the tubule?
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low hydrostatic pressure in capillary
high osmotic pressure in capillary |
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bulk ________ of substances occurs in the proximal tubule
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reabsorption
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the proximal tubule is ________ to water
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permeable
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how are organic solutes transported across the tubule?
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by coupling with Na transport
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which pump is crucial to the tranport of many solutes?
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Na pump - Na/K/ATPase
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where is the Na pump located?
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in the basolateral membrane of the tubular cells
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what does it do?
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pumps IN 2 K
pumps OUT 3 sodium into the capillary generates a gradient for sodium reabsorption |
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what does the gradient consist of that the Na pump generates?
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electrical gradient: -ve inside the cell
chemical gradient: low intracellular Na |
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where does the Na pump NOT occur in the nephron?
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intercalated cell of DCT
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what are the four ways sodium is transported in the proximal tubule and what percentage are attributed to each?
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Na/H exchanger
alone transcelluarly 30-60% paracellularlly through tight junctions into lateral space 25-50% coupled to organic substances 10% |
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describe the reabsorption of bicarbonate in the proximal tubule
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hydration of Co2 inside cell forms carbonic acid, catalysed by intracellular CA
the H+ is secreted through Na/H and the HCO3 in the lumen reacts with H+ forms carbonic acid this is then dissociated into water and carbon dioxide by apical CA water and carbondioxide reabsorbed into cell |
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how much bicarbonate is reabsorbed in the proximal tubule
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80-90%
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can reabsorption in the proximal tubule correct a metabolic acidosis
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no! the bicarbonate from the blood is filtered and then reabsorbed
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how do the organic solutes leave the tubule and get into the capillary?
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by passive diffusion
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describe water transport in the proximal tubule
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high permeability to water
transcellular: AQP-1 in the apical and basolateral membrane paracellulary across LEAKY tight junctions |
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what factors / forces allow water reabsoption in proximal tubule?
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low capillary hydrostatic pressure
high capillary osmotic pressure high oncotic pressure in capillary high hydrostatic pressure |
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what is solvent drag and what ions does it carry?
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drag from osmotic flow of water
affects Na, Cl, K, Ca, Mg particularly Ca and K |
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describe K transport in proximal tubule
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paracellular: by solvent drag
also some diffusion out of cell transcellularly due to increased K inside cell from Na/K pump 67% reabsorbed |
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describe urea reabsoption in proximal tubule
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paracellular and transcellular routes
50% reabsorbed dependant on water reabsorption |
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describe chlorine reabsorption in proximal tubule
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80% reabsorbed
paracellulary: solvent drag transcellularly: base/Cl pump coupled to Na/H pump base = oxalate, formate, OH- |
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how does the filtrate compare to plasma when it enters the loop of Henle? (in terms of concentration)
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isotonic to plasma
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describe what occurs in the descending thin limb
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highly permeable to water due to AQP1 - absorbs 15% of water
not very permeable to NaCl - movement mostly by passive diffusion |
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describe what occurs in the ascendign thin limb
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little reabsorption of water
20-30% of Na reabsorved |
