Lecture 42 - Clearance and Glomerular Filtration Flashcards
(46 cards)
The concentration of insulin in plasma is 4 mg/L. This filters into the urine first through the glomerular capillary and into Bowman’s space. The urine has a concentration of insulin of 300 mg/L. 2.4 L is excreted in 24 hours, thus 0.1 L/hr volume. What is the GFR?
7.5 L/hr
(300 * 0.1)/4
-no reabsorption of insulin
-no secretion of insulin
Creatinine in humans is secreted by the _______. Creatinine can be used to estimate GFR, =
tubules; (0.9*calculated GFR)
The critical point of renal failure is ______
1/Pcr ~0.1 in (dL/mg)^-1
The renal clearance of a substance is the ________ of plasma from which that substance in the plasma is completely cleared by the kidneys per ________.
Volume, unit time
The renal clearance of insulin is the volume of plasma which is completely cleared of insulin, since it fits the 5 criteria, is the volume of plasma filtered, that is _____.
GFR
C<in/sub>=GFR
How much plasma must be completely cleared to supply the excreted mass of glucose?
GFR=180 L/day
P<PO4/sub>=1 mmol/L
U<PO4/sub>V= 20 mmol/day
20 L/day (phosphate clearance)
The organic anion para-aminohippurate (PAH) is secreted by _________.
proximal tubule cells
PAH is freely filtered [T/F]
True
When [PAH] is low, virtually all PAH that escapes filtration is __________ [secreted/reabsorbed].
secreted
PAH is not reabsorbed [T/F]?
True
What is the net effect on the plasma with PAH being secreted?
All the plasma supplying the nephrons is completely cleared of PAH
If all PAH is cleared from all the plasma flowing through the entire kidney, its clearance would measure ________.
Total renal plasma flow (RPF)
PAH clearance measures _____, which is 85-90% of RPF.
effective renal plasma flow (ERPF). This is because about 10-15% of total renal plasma flow supplies non-filtering and non-secreting portions of the kidney; where PAH not cleared.
PAH clearance is a substance used to measure ______.
effective renal plasma flow (ERPF)
C<PAH/sub> = ________ [RPF/ERPF] =
ERPF = (U<PAH/sub> * V)/P<PAH/sub>
Effective renal blood flow (ERBF) can be determined by:
(ERPF)/(1-V<C/sub>
Vc= hematocrit, fraction of blood occupied by erythrocytes
C<osm/sub> is the osmolar or free water clearance, allows the determination of the ability of the kidney to separate solute and water, that is water conservation or water secretion.
U<Osm/sub> * V / P<Osm/sub>
Free water clearance can be used as an indicator of how the body is regulating _____.
water
Free water clearance is the volume of blood plasma that is cleared of _________ per unit time. C<H2O/sub>=
solute-free water
C<H2O/sub> = V-C<osm/sub>, where V is urine flow rate
Water balance is when UFR=_____.
UFR=C<osm/sub>
(aka Posm=Uosm)
Overhydration is when UFR>_____.
C<osm/sub>
(aka Posm>Uosm)
Dehydration is when UFR<_____.
UFR<C<osm/sub>
(aka Posm<Uosm)
How does blood pressure across the renal vascular network compare between afferent and efferent arterioles vs glomerular capillary?
There is a sharp decrease in pressure across the afferent and efferent arterioles. There is relatively high hydrostatic pressure maintained along the glomerular capillary
Through the renal artery, blood pressure drops sooner at the ____________ nephron vs later in the ___________ nephron.
Juxtamedullary, superficial
