Renal Physiology I - Wall Flashcards
Which ion determines size of the extracellular fluid volume?
Na
Which ion has the greatest effect on blood pressure?
Na
What is the major body anion?
Cl
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)
What is 1-alpha hydroxylase?
Enzyme in kidney in charge of final synthesis step for active vitamin D
What is bradykinin?
A vasodilator important for regulating vasofiltration rates
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
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
What is neutral balance?
Diet intake + endogenous production = excretion rate
What is positive balance?
Intake + endogenous production > excretion, leading to increased total body content
What is negative balance?
Intake + endogenous production < excretion, leading to decreased total body content
About how much of the glomerular filtrate is reabsorbed?
~99%
How does filtrate differ from blood?
Filtrate doesn’t have cells or large proteins
What is always the best measure of overall kidney function?
GFR
Is water ever secreted into the tubule downstream from the glomerulus?
NO
Where are the kidneys located anatomically?
Retroperitoneal from T12-L3
Which part of the kidney is most perfused?
Cortex, with about 98% of total kidney flow
What is the area called where the ureters, vessels, lymphatics, and nerves enter the kidney?
Renal hilus
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
What is the function of prostaglandins secreted by the kidney?
Autoregulation of CFR, particularly via PGI2 and PGE2
What is endothelin?
Made during endothelial injury; very powerful vasoconstrictor
How is potassium eliminated by the kidney?
Secretion (as opposed to filtered out at the glomerulus)
Where do the glomeruli reside in the kidney?
Cortex
Describe the flow of urine from the collecting duct
Duct –> papilla –> minor calyx –> major calyx –> renal pelvis
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
