L06: Renal Tubular Function 2 Flashcards
What structure after the proximal tubule do we get
Loop of henle
What is the loop of henle divided into
Descending limb
Ascending limb
What is the role of the ascending limb
Create a high osmolarity interstitial space in the medulla so water from the descending and collecting duct is reabsorbed.
Which layer is the loop of henle found in
Medulla
How is water reabsorbed in the loop of henle
Through the gaps between cells.
Which ions are reabsorbed in the thick ascending limb
Sodium
Chloride
Potassium
Describe the reabsorption of the sodium, potassium and chloride from the apical membrane through the basolateral membrane into the interstitial space
Apical membrane
1) sodium, potassium and chloride cotransporter called NKC22 brings in sodium,potassium and chloride into the cell.
Basolateral membrane
2) sodium leaves out via the 3na+/2k+ pump
3) potassium leaves via the potassium channels
4) chloride leaves via the chloride channels into the interstitial space
Is the thick ascending limb permeable or impermeable to water
Impermeable to water
Why is the thick ascending limb impermeable to water (think of how water moves through cells)
The gaps between cells are blocked so water can pass through the gaps.
What is furosemide
Diruetic
What is the role of a diuretic
Keep water in urine (lose lots of urine)
How does furosemide act as an diuretic
Blocks, sodium, chloride and potassium cotransporter in the thick ascending limb.
When is furosemide used
In cardiac and renal failure (volume overload)
What are the side effects of using furosemide
Naturesis (loss of sodium)
Diuresis (loss of water)
Hypokalemia (loss of potassium)
Is the descending limb permeable or impermeable to water
Permeable
Which mechanism allows the movement of water from the descending limb to the interstitial space
Countercurrent mechanism
What is the countercurrent mechanism
1) As the thick ascending limb pumps sodium, chloride and potassium into the interstitial space, it creates a high osmolality in the space.
2) this creates a osmolality gradient in the space
3) water from the descending limb therefore flows into the medulla
What is the next structure after the loop of henle
Distal tubule
Where is the distal tubule situated
Cortex
Which ions are absorbed in the distal tubule
Sodium
Chloride
How are the ions absorbed in the distal tubule from the apical membrane through the basolateral membrane
Apical membrane
1) sodium/chloride cotransporter brings the ions into the cell
Basolateral membrane
2) sodium/potassium pump brings sodium out and potassium in
3) the potassium that has entered moves back out through the boas lateral membrane with chloride by the potassium/Chloride transporter.
What inhibits the sodium/chloride transporter on the apical membrane
Thiazides
What is thiazides therefore classed as
Diuretics
What is the role of diuretics
Lose lots of volume of water in urine
Which structure comes after the distal tubule
Collecting duct
Which molecules are absorbed in the collecting duct
Water
Sodium
Urea
Describe the process of reabsorption of sodium and water from the apical membrane through the basolateral membrane
Apical membrane:
1) water moves in through AQP2 channels
2) sodium moves in via sodium channels
Basolateral membrane
3) AQP3 allows water to move into the medullary interstitial space
4) sodium moves out by sodium potassium pump
What happens to the potassium that is brought into the cell through the basolateral membrane
Moves out into the filtrate of the collecting duct via potassium channels on the apical membrane
Which hormone increases the number of AQP2 on the apical membrane
ADH/vasopressin
Which hormone from the adrenal cortex increases the synthesis of sodium channels
Aldosterone
What is the role of amiloride
Inhibit sodium channels on the apical membrane
What is the role of spironolactone
Blocks the action of aldosterone to synthesis sodium channels
How is urea reabsorbed in the collecting duct
1) via UT-A1 channels
2) this also increases the osmolality in the interstitial space so more water is reabsorbed from the descending limb of the loop of henle
Which channel reabsorbs urea
UTA1 in the collecting duct
Which hormone increases the expression of UTA1
ADH
Where are urea reabsorbed so that some of the urea in the medulla enter back the nephron
The collecting duct
Which channel reabsorbs the urea
UTA2
What does the secretion and reabsorption of urea known as
Urea countercurrent
