Introduction to Renal Physiology Flashcards
What part of kidney contains glomeruli and convoluted tubules?
Cortex
What part of kidney contains think loops of henle and collecting ducts?
Medulla
Salt Conserving Nephron
Juxtamedullary Nephron
Salt and Water Wasting Nephron
Cortical Nephron. Used when hydrated
Where is primary urine formed?
In glomerulus
Can kidney function in gluconeogenesis?
Yes
Pain sensation in kidney
Splanchnic nerve originating in renal pelvis.
Innervation of kidney?
Sympathetics from celiac and mesenteric plexus. Some parasympathetic innervation, function unclear.
Purpose of the glomerulus
Filtration.
Concentration of filtrate
Same as concentration of plasma, just lacking large proteins.
Hydrostatic pressure and resistance of glomerular capillaries
High pressure, low resistance. Pressure stays constant throughout capillary.
Juxtaglomerular apparatus
Distal tubule comes back to own glomerulus and passes next to afferent arteriole. Allows for feedback regulation of afferent tone and GFR. Renin is released from the macula densa.
Path of material from blood place to urinary space
Material flows past endothelial cells, through the basement membrane (which acts as a sieve), through slit diaphragms into the slit pore (formed by podocytes), into the urinary space.
How does the glomerulus control size and charge of material flowing through filtration barrier?
Barriers are covered in negatively charged proteins.
What will flow more freely through the filtration barrier: Cations or Anions? Does size matter?
Cations. Smaller is easier.
How is Kf calculated?
Proportional to SA and K (hydraulic conductivity, ease with which water moves across a barrier).
Equation for SNGFR
Kf [(Pgc -Pbs - πgc)]. There is no πbs in healthy people.
Is GFR determined by blood flow or pressure?
Pressure.
What happens to GFR if there’s a kidney stone?
Pbs increases, GFR decreases.
What happens to GFR is there’s renal artery stenosis?
Pgc decreases, GFR decreases.
Which has a higher Kf: systemic capillary or glomerular capillary? Why?
Glomerular Capillary. Higher hydraulic conductance.
Clearance definition and equation
The volume of plasma from which a substance is completely removed per unit time. Provides a way to quantify kidney function.
Cx = (Ux * V)/Px
Where Ux is urine concentration, V is urine flow, Px is plasma concentration.
How does clearance relate to GFR
They are equal if the compound is freely absorbed, not reabsorbed or secreted, not broken down, and not synthesized in the kidney.
What two markers are used to measure GFR by clearance?
Inulin and Creatinine
Equation for amount of substance filtered
Px * GFR
Equation to determine amount of compound in urine
UxV = (PxGFR) + TSx - TRx
Amount in urine = amount filtered + amount secreted - amount reabsorbed
How can Cx and CCr/Cin relate?
If Cx = CCr, Cx=GFR.
If Cx > CCr, net secretion
If Cx < CCr, net absorption.
How is GFR measured clinically?
By measuring plasma creatinine and BUN.
What determines how much creatinine is in plasma? Normal plasma creatinine?
Plasma creatinine is inversely proportional to elimination. So, the more excreted, the less plasma creatinine there is. Production is constant, so we don’t have to worry about that. Normal is 0.7 - 1.2 g/dL.
What is the BUN value dependent on?
State of hydration.
