nephron physiology Flashcards
what are the features of the cell for the reabsorption of molecules in the kidney ?
the side that faces the urine is polarized called the apical membrane
the other side is called the basolateral membrane
where is the highest rate of reabsorption in the nephron ?
the proximal convoluted tubules
what solutes are reabsorbed in the PCT ?
100% of glucose and amino acids
water bicarb and NaCl 67%
what allows for the reabsorption of these substances in the PCT ?
the sodium potassium pump on the basolateral side of the cell
this creates a low concentration of sodium inside the cells
which allows for 100% of glucose to be reabsorbed
how is the reabsorption of chlorine be explained ?
by the constant excretion of anions
how is water reabsorbed in the PCT ?
once the sodium reaches a sufficient level in the interstitium , water follows through through the para cellular route
what is the transporter for glucose ?
sodium glucose co transporter
what are the levels of serum glucose that will result in glucose in the urine ?
start once at 160 mg/dl then a straight line rising at 360 mg due to saturation of cells
why is some glycosuria normal in pregnancy ?
because there is an increase in GDR but a decrease in glucose reabsorption
what is the best method for screening for diabetes in pregnancy ?
serum glucose testing
how are amino acids uptaken in the PCT ?
with a sodium co transporter as well
what is hartnup disease ?
a lack of tryptophan transporters in the proximal tubule
this leads to tryptophan deficiency
which causes niacin deficiency
leading to a skin rash resembling pellagra ( rash in sun exposed areas)
will find amino acids in the urine
hoe is bicarb reabsorbed in the proximal tubule ?
through the sodium hydroegn pump
el hydrogen eli 5arag combines with the HCO3 and forms H2Co3
then with carbonic anhydrase
Co2 and h2O are formed
taken up by the cell and then inside the cell CA forms everything again and we wend up with bicarb which enters the interstitium
what are the clinical correlations with proximal tubule bicarb absorption ?
1- the use of carbonic anhydrase inhibitors , weak diuretics by blocking sodium reabsorption , resulting in bicarb in the urine
2- type 2 renal tubular acidosis - causes metabolic acidosis due to lack of bicarb reabsorption
what is fanconis syndrome ?
happens due to loss of proximal tubule function
no reabsorption of bicarb , glucose , amino acids
what is the presentation of fanconis syndrome ?
polyuria
polydyspsia
glucose in the urine
normal serum glucose
hypokalemia
amino acids in urine
ddx of amino acids in urine ?
hartnup
fanconis anemia
what are the associations with the inherited form of fanconis syndrome ?
inherited form is associated with cystinosis
which is a lysosomal storage disease associated with an accumulation of cystine in the PCT
what are the acquired causes of fanconis syndrome ?
lead poisoning
multiple myeloma
cisplatin
tenofovir
what are the different interpretations for the concentration changes graph ?
if the TF/p > 1 that means the solute is being reabsorbed less quickly than water
if the TF/p = 1 that means the soute is being reabsorbed in the same rate as water
if the TF/p < 1 the solute is being absorbed more quickly than water
what are the functions and the features of the thin descending loop of henle ?
impermeable to NAaCL
concentrates the urine
makes the urine hypertonic
what happens to the osmolarity of the urine in the thin loop of henle ?
increases drastically
what are the solutes responsible for the high osmolarity ?
sodium
chlorine
urea
what is the difference in function between the thin and thick ascending loop of henle ?
the thin ascending loop of henle - water stays in and sodium and chlorine go out
the thick part - more sodium is activley transported outside of the lumen and water stays
