Renal Excretory Function Flashcards
3 parts of the glomerular filtration barrier
Capillary endothelium
Basement membrane
Podocyte foot processes
What protein is lost into urine in nephrotic syndrome
Albumin
Where is the plasma concentrated to an ultra filtrate
Bowman’s capsule
First step of urine formation
Production of plasma ultrafiltrate
What determines what substances enter the ultrafiltrate
Net filtration pressure
Podocyte slit pores
Molecule size
Molecule charge
What molecules moves freely at the glomerulus
Water
Electrolytes
Urea
Amino acids
GFR
Total amount of fluid filtered through the glomerulus
What happens to the majority of fluid filtered in the glomerulus
Reabsorbed
Why is creatinine used to measure GFR
Freely filtered by glomerulus
Not reabsorbed
Measurable
Produced by body
Already at steady state conc in blood
Does creatinine clearance over or under estimate GFR by 10-20%
Overestimates
Why does creatinine clearance overestimate GFR by 10-20%
Peritubular capillaries secrete creatinine
Creatine clearance calculation
(Urine conc x urine vol) / plasma conc
How can GFR be measured
Creatinine clearance
Nuclear medicine scan
How can GFR be estimated
MDRD equation - CAGE
Cockcroft gault equation
What variables are needed to out into the MDRD equation for estimating GFR
CAGE
creatinine
Age
Gender
Ethnicity
What can make GFR from creatinine clearance unreliable
Raised serum creatinine in muscular individuals
Low serum creatinine in malnourished individuals
Raised serum creatinine in individuals on drugs that inhibit Tubular creatinine secretion
Does raised serum creatinine cause an over or underestimattion of GFR
Underestimate
Is the brush border on the apical or baso lateral side of tubule cells
Apical
What limits water and solute movement between tubular cells
Tight junctions
How does urea move from the tubular lumen to interstitium in the proximal tubule
Passive diffusion
How do sodium phosphate glucose and amino acids move from the tubular lumen into tubular cells in the proximal tubule
Secondary active transport
How many Na ions are transported from the tubular cell to the interstitium for very 2 K ions transported from the interstitium to the tubular cell in the proximal convoluted tubule
3
Are sodium and potassium transported by primary or secondary active transport in the proximal convoluted tubule
Primary
What do defects in the apical Na/cystine cotransporter In the proximal tubule cause
Cystinuria
What do defects in the Na/glucose cotransporter in the proximal tubule cause
Renal glycosuria
What do defects in the basolateral Na/HCO3 cotransporter in the proximal tubule cause
Proximal RTA
What do defects in the apical Na/K/2Cl cotransporter in the thick ascending loop of henle cause
Bartter type 1
What do defects in the apical Na-Cl cotransporter in the distal tubule cause
Gitelman’s
What are the 2 parts of the proximal tubule
Proximal convoluted tubule - 1st 2/3
Proximal straight tubule - final 3rd
Where does 80% of solute reabsorbance occur
Proximal tubule
What is pumped out of the descending loop of henle
Water
What substances leave the ascending loop of henle
Sodium
Potassium
Chloride
Calcium
Magnesium
How is high solute concentration maintained deep in the medulla
Vasa react carry salt from top of medulla to deep medulla
What is the thick ascending limb impermeable to
Water
What ion is transported by both secondary active and paracellular transport in the ascending loop of henle
Sodium
Function of the distal nephron
Potassium excretion
Na delivery to collecting duct regulated
Urine acidification
What determines urine conc in the collecting tubule
ADH
Renal threshold
Concentration of a substance dissolved in the blood above which the kidneys begin to remove it into the urine
What happens when the renal threshold of a substance is exceeded
Some of the substance remains in urine
What is the renal threshold for glucose
10mmol/L
Osmotic diuresis
Excess solute in the tubular fluid attracts water and increases urine volume
