(DSA) Introduction to Renal Blood Flow and GFR | (Pierce) Flashcards
What is this structure?
Glomerulus
In order for filtration to occur, what three layers must the particulate cross through?
- Capillary Endothelium
- Glomerular basement membrane
- Podocyte epithelium
Describe the movement of fluid from the capillary lumen…
Capillary lumen –>
Capillary endothelium –>
Glomerular basement membrane –>
Podocyte epithelium –>
BOWMANS CAPSULE
What is shown in this image?
View seen from the capillary side
Holes = fenestrea of the endothelial cells
What are the arrows pointing at?
*fuzzy border = Biogel
Glomerular endothelium glycocalyx forms a biogel in the endothelial lumen
What is the major cell adhesion molecule that specifically functions in the glomerulus?
Function?
NEPHRIN
Nephrin blocks Larger proteins from entering bowmans space
*frequently absent in diseased renal states
Any molecule less than _____ angstroms are freely filtered
20
Any molecule greater than _____ angstroms are not filtered
42
What are podocytes?
Cells in bowmans capsule that wrap around capillaries of the glomerulus
What passes through the filtration barrier?
Freely filtered?
Water
Small solutes (glucose, amino acids, electrolytes)
What is not freely filtered through the filtration barrier?
- Large molecules (proteins)
- Formed elements (cells)
- Miniscule amounts of protein are filtered
*Tamm-Horsfall protein
What molecules are more freely filtered,
Cations or Anions?
CATIONS!!! ++++++++++
What does the cortex contain?
How are they organized?
Renal corpuscles, coiled blood vessles, coiled tubules
Intertwined randomly like plate of spaghetti
What does the medulla contain?
How are they organized?
Straight blood vessels and Straight tubules
Organized in parallel array like bundles of pencils
RBF is regulated…
Minute-by-minute oversight
*For example: during intense exercise, the renal fraction of blood flow decreases because blood is shunted to the musculature
What is filtered load?
The amount of a substance that is filtered into the bowman’s space per unit time (mg/min)
How do you calculate filtered load?
FL = GFR x Px
Equation for urinary excretion?
Amount filtered - Amount reabsorbed + amount secreted = Urinary Excretion
Equation for tubular reabsorption?
Glomerular filtration - Urinary excretion + Amount secreted
If excretion > filtration then…
Tubular secretion must have occured!!!
Equation for urine exretion rate?
Urine excretion rate of x = Ux x V
Ux= the concentration of that substance in the urine in a given volume
V=Urine flow rate, rate at which urine is produced
How do you calculate Ux?
Ux= concentration of X (Ux) = the concentration of that substance in the urine in a given volume
How do you calculate V?
V= Urine flow rate, the rate at which urine is produced
What is renal clearance?
Renal Clearance (C) is the rate at which substances are removed (cleared) from plasma)
IT’S A FLOW RATE
What are the units for renal clearance (C)?
Volumer per unit time
(mL/min, L/hour, L/day)
What is the equation for renal clearance?
What is the glomerular filtrate?
Volume of plasma filtered into combined nephrons of both kidneys per unit time (mL/min)
What is the equation for filtration fraction?
FF = GFR / RPF
GFR= glomerular filtration rate
RPF = renal plasma flow
*FF is typically 20% of RPF
Describe the relationship between filtration fraction and glomerular oncotic pressure
What is filtered load?
A rate in mg/min
What is filtration fraction (FF)?
A ratio of GFR to RBF
What percentage of the filtered load of sodium is reabsorbed per day?
GFR is directly proportional to renal clearance under these conditions:
- Substance must be freely filterable in the glomeruli
- Substance must be neither reabsorbed nor secreted by the renal tubules
- Substance must not be synthesized, broken down, or accumulated by the kidney
- Substance must be physiologically inert
What is an example of a substance that has the GFR = C?
Inulin
Creatinine
In clinical situations, the GFR of a patient is usually determined by measuring the __________
Clearance of creatinine
Sympathetic stimulation causes:
Vasoconstriction
Renin release + RAAS
Na-K ATPase activity; Increased Na+ reabsorption
INCREASED BLOOD PRESSURE
What are the receptor subtypes for:
Plasma creatinine concentration and GFR are _________ proportional
Inversely
What is BUN?
Blood urine nitrogen
What can PAH (Para-aminohippuric acid) be used for?
Estimating renal plasma flow
*We can assume that all the PAH presented to the kidney appears in the urine
