Tubular function 1 Flashcards
What are the plasma concentrations of Na+, K+, Cl-, HCO3-, H+, and C6H12O6 like compared the concentrations in the ultra filtrate
Similar concentrations
What is the plasma protein concentration like compared to the concentration in the ultra filtrate
It far exceeds
In a normal 70kg person, what is the normal GFR
120ml/min
IN a normal 70kg person, what is the normal RPF
600ml/min
In a normal 70kg person, what is the PCV
40%
In a normal 70kg person, what is renal blood flow
1L/min
In a normal 70kg person, what is the cardiac output
5L/min
What is between the peritubular capillary and the tubular epithelium
Peritubular fluid
What is the basolateral membrane
The membrane closest to the peritubular fluid
What is the membrane called closest to the lumen
Apical/luminal membrane
What are the transport pathways in epithelial cells
Transcellular- across cells (can be bidirectional)
Paracellular-between cells
Where are sodium pumps located in the kidney
Exclusively in the basolateral membrane
What do the sodium pumps do
Pump sodium out of cell in exchange for potassium. Decreases intracellular Na+ conc in relation to the outside and so the Na+ wants to move across the electrochemical gradient from the tubular lumen, into the epithelium and then across into the peritubular fluid and then into the peritubular capillary
What does the low pressure of the peritubular capillaries mean
Favours reabsorption
Why is the proximal tubule highly water permeable
Because it has leaky tight junctions and aquaporins
What is the water gradient like in the proximal tubule
Tubular Fluid is approximately isosmotic with the plasma
What are the mechanisms for the entering of sodium ions into the tubular epithelium from the apical membrane
1) Sodium - Hydrogen exchange
2) sodium entry coupled with other solutes (simple mechanisms)
3) On its own through membrane channels
4) Passively via tight channels
How do bicarbonate ions get reabsorbed into the blood (i.e. get from the tubular fluid into the peritubular capillaries)
- The apical membrane is impermeable to bicarbonate ions
- Bicarbonate ions combine with H+ which has entered the lumen from the Na+-H+ pump to form carbonic acid
- Carbonic anhydrase dissociates carbonic acid into co2 and water which moves into the cell
- Carbonic acid in the cell associates the co2 and water back into carbonic acid
- The H+ dissociates to form bicarbonate ions
- The H+ leaves again via the Lumen
- The bicarbonate ions leave with the Na+ into the peritubular fluid and into the peritubular capillaries
IN an alkalosis (excess bicarbonate and too little H+), what do the kidneys do
Excrete more filtered bicarbonate so less get absorbed
In an acidosis, what do the kidneys do ti help
You can’t turn up reabsorption because kidneys are already working at maximum so they can turn up the production of bicarbonate to compensate
How does potassium reabsorption occur in proximal tubule
Paracellular transport
How does cl- reabsorption occur
Transcellular transport
Paracellular transport
