Resabsorption and Secretion Flashcards
what is different between Pgc and Ppc
Pgc is greater than Ppc, because filtration at glomerulus but reabsorption at peritubular
other than hydrostatic forces what other force is in favour of reabsorbtion into the peritubular capillaries
oncotic pressure (20% of plasma is in bowman’s capsule meaning higher protein conc in capillary)
true/false many substances are reabsorbed by carrier mediated transport systems
true - glucose, amino acids, acis, sulphate and phosphate ions all require carriers
what is Tm
the maximum transport capacity (the rate at full saturation)
what happens when Tm is exceeded
the excess is excreted into urine
what is the renal threshold
the plasma concentration of a substance at which full saturation and hence Tm occurs
what is the renal threshold for glucose
10mmoles/L
what happens to the glucose at a conc of 15mmoles/L
all 15mmoles/L will be filtered, 10mmoles/L will be reabsorbed and 5mmoles/L will be excreted
true/false there is a threshold for glucose filtration
false - glucose is freely filtered from glomerulus
at what concentration will the kidneys begin excreting glucose
10mmoles/L
true/false Tm for amino acids is low and they are often excreted
false - Tm for amino acids is set so high that excretion does not occur
how do kidney tightly regulate a substances concentration
by having a Tm whereby normal plasma concentration causes saturation
where does most Na+ reabsorption occur
proximal tubule (about 65-75%)
how is Na+ reabrobed
by active transport driven by Na+ pumps
where are Na+ pumps
basolateral cell surfaces where there is a high density of mitochondria (ATP supply)
process of Na+ moving into interstitial fluid
high conc in tubule and low conc in tubule cell –> Na+ moves in by gradient –> moved out by Na+ K+ ATPase pump
true/false Na+ is not usually membrane permeable but proximal tubule has higher permeability
true - it is achieved by large surface area of microvilli and large number of Na+ ion channels
what facilitates negative ions like Cl- reabsorption
the electrical gradient created by Na+
what facilitates water’s reabsorption
the osmotic force created by all the ions moving across
how much urea is reabsorbed
only about 50%, onyl moderately permeable
true/false the active transport of Na+ is important for inducing lots of other resorption
true - any impairment to it’s active transport results in a disruption of renal function
effect of high [Na+] on glucose transport
stimulates it
glucose transport and connection to Na+
Na+ uses SGLT transporter to get into cell and pulls glucose with it (like in gut) –> out cell by GLUT2 –>Na+ out by Na+K+ATPase
sites of secretion along tubule
proximal, distal and collecting duct
