Term
| What are the forces that govern the movement of fluid across the capillary wall? |
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Definition
1) starling's forces
2) specific membrane properties |
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Term
| What are unique features of the glomerular capillary in comparison to systemic capillaries? |
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Definition
1) increased hydrostatic pressure
2) increased permeability
3) uniquely interposed between two arterioles |
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Term
| What is the major determinant for the hydrostatic pressure (P)? |
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Definition
1) glomerular perfusion pressure:
- systemic blood pressure
- afferent/efferent arteriolar resistance |
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Term
| What are the major determinants for the oncotic pressure? |
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Definition
| 1) protein concrentration of the capillary blood and the filtrate |
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Term
| What is the equation to calculate the net filtration pressure? |
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Definition
1) P_UF = deltaP - deltaPI
2) P_UF = (Pgc-Pbs) - (PIgc - PIbs)
3) P_UF = Pgc - (Pbs + PIgc); PIbs =0 |
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Term
| How do the glomerular hemodynamics change along the length of the capillary |
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Definition
1)loss of a protein-free filtrate, oncotic pressure progressively increases (decline in P_UF)
2) hydrostatic pressure remains stable (filtration washout)
3) P_UF falls from highest level at the afferent end to its lowest at the efferent end |
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Term
| How does the glomerular filtration depend on membrane characteristics? |
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Definition
1) highly permeable to water and low molecular weight solutes?
2) impermeable to cells and large molecules (colloids)
3) filtrate is composed of water and crystalloids at the same concentration as plasma
4) large molecules are reflected
5) anionic molecules are reflected |
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Term
| What is the equation for the ultrafiltration coefficient? |
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Definition
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Term
| What is the equation to calculate the glomerular filtration rate? |
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Definition
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Term
| What are conditions that would increase GFR wrt. K_f, P_gc, P_bs, and PI_gc? |
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Definition
1) mesangial cell relaxation increases glomerular capillary surface area
2) afferent arteriole dilation; efferent arteriole constriction; systemic hypertension
3) N/A
4) hypoalbuminemia; high renal plasma flow |
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Term
| What ist he equation used to calculate the filtration fraction? |
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Definition
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Term
| What is auto-regulation of GFR? |
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Definition
| 1) the unique interposition of the glomerular capillary between two resistance vessels that allows for regulation of P_gc under varying renal perfusion pressures and flows |
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Term
| What happens to P_gc, RPF, and GFR with dilation of the afferent arteriole? constriction of efferent arteriole? |
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Definition
1) increase P_GC, RPF, GFR
2) decrease RPF; increase GFR, P_GC |
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Term
| Which is most important at high pressure: afferent arteriolar tone, or efferent arteriolar tone? low pressures? |
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Definition
1) afferent arteriolar tone
2) efferent arteriolar tone |
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Term
| What are local factors that help mediate GFR regulation? |
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Definition
1) vascular tone
2) tubuloglomerular feedback (macula densa - Cl); low flow, Cl = efferent vasoconstriction and inc. FF; high flow, Cl = afferent constriction and reduced FF |
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Term
| What are hormonal factors that help mediate GFR? |
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Definition
1) angiotensin II
2) epi/NE
3) prostaglandins
4) others: vasopressin, endothelin, DA, EDRF, DA, kinins, ANP |
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Term
| What is the effect of AII on GFR? |
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Definition
1) efferent arteriolar vasoconstriction
2) increased filtration fraction
3) increased systemic vascular tone |
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Term
| What is the effect of ACe inhibitors and ARBs? |
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Definition
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Term
| What is the effect of sympathetic tone on the GFR? |
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Definition
1) baroreflex activation of the carotied body, leading to systemic arteriolar constriction, including afferent and efferent arterioles of the kidney
2) proportionately greater efferent arteriolar constriction limits fall in GFR from reduced RPF by increasing P_GC (increased FF) |
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Term
| What is the effect of prostaglandins on the GFR? |
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Definition
1) released due to AII and symp stim
2) vasodilate afferent arteriole
3) inc. P_gc, w/ inc. RBF despite systemic vasoconstrictors
4) blocked with NSAIDS will lead to hypoperfusion |
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Term
| What is the equation for calculating the GFR for an ideal filtration marker? What are the characteristics of an ideal filtration marker? |
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Definition
1) GFR = Cx = Ux*V/Px
2) substances that is freelyfiltered from the plasma at the glomerulus and neither reabsorbed nor secreted by the tubules |
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Term
| What is an example of an ideal filtration marker? |
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Definition
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Term
| What is an ideal marker for clearance calculation of RPF? |
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Definition
| 1) substance that is not only freely filtered but is completely secreted into the tubules |
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Term
| What is an example of a marker that might be used to calculate RPF from the clearance? |
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Definition
| 1) PAH (para-amino hippuric acid) |
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Term
| What is the normal value for the GFR? |
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Definition
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Term
| What are major factors that alter the GFR? |
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Definition
1) lean BMI
2) sex
3) age
4) diet |
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Term
| What are the major techniques for estimating GFR? |
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Definition
1) ideal filtration marker: inulin (gold standard), creatinine
2) serum creatine
3) empiric formulae
4) radionucleotide scan |
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Term
| What are the criteria for an ideal filtration marker for estimation of GFR |
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Definition
1) freely filtered, not secreted or absorbed by tubule
2) inexpensive and readily available
3) nontoxic and not metabolized
4) easily measured |
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Term
| Describe the characteristics of inulin that make it the gold standard for fitration marker for GFR estimation. Creatinine? |
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Definition
1) freely filtered, not secreted not reabsorbed; not readily available and expensive, accurate, requires IV infusion
2) requires timed urine collection w/ steady-state plasma level; filtered and secreted but not reabsorbed; no infusion; limited accuracy |
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Term
| What are factors that may determine the decision to use radionucleotide scan to estimate GFR? |
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Definition
1) expensive
2) varying utility based on ease of measurement and characteristics of the filtration marker |
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