Renal Physiology I - Wall Flashcards by Matt McCulloch

Which ion determines size of the extracellular fluid volume?

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Which ion has the greatest effect on blood pressure?

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What is the major body anion?

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What are the major waste products that the kidney is in charge of clearing?

Urea (from protein), creatinine (from muscle metabolism), and uric acid (from nucleic acid metabolism)

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What is 1-alpha hydroxylase?

Enzyme in kidney in charge of final synthesis step for active vitamin D

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What is bradykinin?

A vasodilator important for regulating vasofiltration rates

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What are the three ways through which the kidney as an organ maintains blood pressure?

1) Homeostasis of Na and H20
2) Controling renin-angiotensin system
3) Producing vasodilatory substances

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Does the kidney have an important role in regulating insulin levels?

Yes because it excretes insulin. In instances of kidney atrophy, less cleared insulin means hyperglycemia

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What is neutral balance?

Diet intake + endogenous production = excretion rate

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What is positive balance?

Intake + endogenous production > excretion, leading to increased total body content

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What is negative balance?

Intake + endogenous production < excretion, leading to decreased total body content

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About how much of the glomerular filtrate is reabsorbed?

~99%

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How does filtrate differ from blood?

Filtrate doesn’t have cells or large proteins

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What is always the best measure of overall kidney function?

GFR

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Is water ever secreted into the tubule downstream from the glomerulus?

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Where are the kidneys located anatomically?

Retroperitoneal from T12-L3

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Which part of the kidney is most perfused?

Cortex, with about 98% of total kidney flow

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What is the area called where the ureters, vessels, lymphatics, and nerves enter the kidney?

Renal hilus

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What type of anemia would you expect to see in someone with a reduced-function kidney?

Less EPO leads to low reticulocytes and thus a normocytic normochromic anemia

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What is the function of prostaglandins secreted by the kidney?

Autoregulation of CFR, particularly via PGI2 and PGE2

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What is endothelin?

Made during endothelial injury; very powerful vasoconstrictor

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How is potassium eliminated by the kidney?

Secretion (as opposed to filtered out at the glomerulus)

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Where do the glomeruli reside in the kidney?

Cortex

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Describe the flow of urine from the collecting duct

Duct –> papilla –> minor calyx –> major calyx –> renal pelvis

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Where is the most common site of urine blockage in males and what is this called?

Prostatic uretha; obstructive uropathy

Where is the ureter most vulnerable to obstruction?

Pelvic-ureteral junction Crossing pelvic brim Urinary trigone (bladder)

Trace the flow of blood starting in the renal artery

Renal artery, segmental artery, lobar artery, interlobar artery at the corticomedullary junction, arcuate arteries, interlobular artery, afferent arteriole, glomerulus, efferent arteriole,

Compare the pressure of juxtamedullary and cortical nephrons?

Cortical nephrons have slightly lower perfusion pressure, being further from aorta

Which type of nephron has the longer loop of Henle?

Juxtamedullary

What are juxtamedullary nephrons particularly important for?

Maximal water conservation and urine concentration Medullary thick ascending limb esp important for Na transport

Why do you not want much perfusion to the medulla?

Want to maintain the hypertonic medulla in order to concentrate urine through secretions

What do the efferent arterioles turn into?

Peritubular capillary network of cortical nephrons

Where does the capillary network in the medulla come from?

Vasa recta

Which types of nephrons are always operating at full capacity?

Juxtamedullary, thus they are at greatest risk for hemodynamic stress

Which proteins lead to congenital nephrotic syndrome when defective?

Podocin or nephrin

What are the key cells in the proteinuric condition?

Podocytes

Which Starling forces promote filtration out of the capillary?

Hydrostatic pressure within capillary | Oncotic pressure within interstitium

Which Starling forces oppose filtration out of the capillary?

Oncotic pressure within capillary | Hydrostatic pressure within interstitium

What is the GFR formula?

LP*S(delP-delTau) Lp - capillary wall permeability S - glomerular capillary SA delP - hydrostatic pressure gradient between capillary and Bowman's space delTau - Oncotic pressure gradient between capillary and Bowman's space

What is the main thing that determines GFR?

High glomerular capillary pressure

Why is oncotic pressure low in Bowman's space?

Because albumin was prevented from entering

What are some features of mesangial cells?

Contractile to adjust filtration rate Macrophage activity Ground material for stabilization of glomerulus structure

When you think proteinuria, you think what?

Dysfunctional podocytes

What process does the macula densa govern?

Tubular-glomerular feedback

What changes to the arterioles occur during hypovolemia?

Afferent relaxes, efferent constricts

What is pressure natriuresis?

Increased urinary flow due to increased perfusion pressure, which results in more Na+ excretion and therefore also water; however this does NOT mean that GFR has changed

What is filtered load?

[Plasma] x GFR of a solute; represents amount of substance in plasma filtered per unit time

What is excretion rate?

[urine] x UFR; represents amount of substance excreted into the urine per unit of time UFR is not autoregulated like GFR is

What is an exogenous example of something used to measure GFR?

inulin

What is an endogenous example of GFR measurement?

Creatinine

Is creatinine exactly the same as GFR?

No, it is ~10 secreted in tubule so measuring creatinine overestimates GFR by 10%

Pinulin x GFR =

Uinulin x UFR

For inulin, filtered load is equal to....

excretion rate

What is the simplified formula for GFR?

([U] x UFR ) / [P]

What is the clearance ratio?

(clearance rate of substance) / GFR

What substances would you expect to have a clearance ratio of ~1?

Inulin, creatinine

What does it mean if clearance ratio is <1 and what is an example?

Solute is filtered but reabsorbed Na

What does it mean if clearance ratio is >1 and what is an example?

Solute is filtered and actively secreted as well K+, H+

What are some reasons a substance could have a clearance ratio of 0?

Too large to be filtered (proteins) Highly protein bound (e.g., meds) Filtered but 100% reabsorbed (glucose/AAs)

How do you measure renal plasma flow?

Using para-aminohippurate (PAH), an exogenous substance that is filtered and also actively secreted to the point of complete extraction in one pass

What is GFR (not formula)?

How much blood passes through glomeruli per minute

What is the clearance of PAH equal to?

Renal plasma flow