Renal Physl 7 Flashcards
What percent of filtered fluid is reabsorbed?
99%
How many liters of urine is produced on average?
1.5L
Why does the kidney filter so much?
To allow the removal of wastes and control of fluid and electrolyte balance
What does the process of water and solute reabsorption from the filtrate to the renal interstitium heavily depend on?
Active transport mechanisms
What do tubular epithelial cells do in reabsorption?
They actively transport solutes out of the filtrate and into the renal interstitium
What does tubular epithelial cells actively transporting solute into the renal interstitium produce?
An electrochemical gradient
How does water get reabsobed?
It follows the solutes through osmosis
What creates a transepithelial electrochemical gradient?
The active transport of sodium ions into the renal interstitium to be reabsorbed
After sodium ions are reabsorbed to the renal interstitium, where is more negative?
The lumen is more negative the the interstitium
What happens as a result of the lumen being more negative and renal interstitium being more positive after sodium ions are actively transported out?
Anions follow the positively charged sodium ions into the interstitium to be reabsorbed
After all the solutes leave the tubule lumen what is the concentration of the filtrate?
The filtrate becomes more dilute compared to the interstium
What happens as a result of the filtrate being more dilute than the interstitium after the solutes enter the interstitium?
The water moves from the tubule lumen to the interstitium and this concentrates the remaining solutes in the tubule lumen
What happens once the filtrate is concentrated due to water moving to the interstitium?
Because the solutes in the lumen are so concentrated it moves down its concentration gradient to the interstitium
What kinds of transport does reabsorption involve?
Transport across tubular epithelial cells as well as paracellular transport
What is transcellular transport?
When solutes pass both the apical and basal lateral membrane of the epithelia cell to get to the renal interstitium
What occurs in the paracellular pathway?
Solutes pass between epithelial cells through cell junction
What does pattern of transport (transcellular or paracellular) depend on?
The permeability of the epithelial cells to each solute and the electrochemical gradient
Where does active reabsorption of sodium ions mostly take place?
At the proximal tubule
What happens since sodium concentration in the lumen is higher than in the cell interior?
Sodium can enter the epithelial cells passively going down its electrochemical gradient at the apical membrane
What kind of channels do sodium ions interact with when going from the lumen to the epithelial cells?
Symporters, antiports, and open leak channels
What channels contribute significantly to sodium reabsorption?
- Sodium hydrogen exchanger or NHE channels
* ENaC (apical epithelial sodium channel)
What transports sodium in the epithelial cell to the renal interstitium?
Sodium Potassium ATPase
What happens as a result of the sodium potassium ATPase actively transporting sodium out of the epithelial cell?
Potassium enters the cell but it can escape back out again through the basolateral potassium leak channels
What can the reabsorption of sodium be linked to?
The reabsorption of other substances through secondary active transport like amino acids, glucose, other ions and metabolites