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Questions and Answers
What percentage of sodium does the ascending limb of loop of Henle absorb?
What percentage of sodium does the ascending limb of loop of Henle absorb?
25%
What type of cotransport occurs in the ascending loop of Henle?
What type of cotransport occurs in the ascending loop of Henle?
Na+-K+-2Cl- cotransporter in luminal membrane
Loop diuretics inhibit:
Loop diuretics inhibit:
Na+-K+-2Cl- cotransporter in luminal membrane
What is the diluting segment in the ascending loop of Henle?
What is the diluting segment in the ascending loop of Henle?
Distal tubule reabsorbs sodium via what co-transporter?
Distal tubule reabsorbs sodium via what co-transporter?
Where do thiazide diuretics inflict their damage?
Where do thiazide diuretics inflict their damage?
What is the role of the loop of Henle?
What is the role of the loop of Henle?
What are the different segments of the loop of Henle?
What are the different segments of the loop of Henle?
What is the thin descending limb most permeable to?
What is the thin descending limb most permeable to?
The thin ascending limb of Loop of Henle is permeable to?
The thin ascending limb of Loop of Henle is permeable to?
What is the importance of the basolateral membrane channeling sodium out of the cell in the thick ascending loop of Henle?
What is the importance of the basolateral membrane channeling sodium out of the cell in the thick ascending loop of Henle?
What apical membrane cotransporter system is targeted by high-ceiling diuretics?
What apical membrane cotransporter system is targeted by high-ceiling diuretics?
What percentage of sodium is reabsorbed by the thick ascending limb of Henle via the paracellular pathway?
What percentage of sodium is reabsorbed by the thick ascending limb of Henle via the paracellular pathway?
Why is the thick ascending limb considered to be the diluting segment?
Why is the thick ascending limb considered to be the diluting segment?
Compare the transfer of NaCl in the thick ascending loop of Henle and the early distal convoluted tubule.
Compare the transfer of NaCl in the thick ascending loop of Henle and the early distal convoluted tubule.
NaCl is reabsorbed by the thick limb of the loop of Henle via what transport mechanism?
NaCl is reabsorbed by the thick limb of the loop of Henle via what transport mechanism?
What is the countercurrent mechanism/system?
What is the countercurrent mechanism/system?
NaCl reabsorption by the thick ascending limb of the loop of Henle results in the generation of a hyperosmotic interstitial fluid in which region of the kidney?
NaCl reabsorption by the thick ascending limb of the loop of Henle results in the generation of a hyperosmotic interstitial fluid in which region of the kidney?
As the dilute urine passes up through the thick ascending loop of Henle, what hormone functions to concentrate urine?
As the dilute urine passes up through the thick ascending loop of Henle, what hormone functions to concentrate urine?
What allows water to leave the tubular lumen into the interstitial fluid?
What allows water to leave the tubular lumen into the interstitial fluid?
What percentage of urea is filtered in the glomerulus and reabsorbed by the proximal tubule?
What percentage of urea is filtered in the glomerulus and reabsorbed by the proximal tubule?
After the proximal tubule reabsorption, where does urea reabsorption occur again?
After the proximal tubule reabsorption, where does urea reabsorption occur again?
ADH permits urea reabsorption in what region of the kidney?
ADH permits urea reabsorption in what region of the kidney?
What type of transport does urea undergo along the inner medullary collecting duct?
What type of transport does urea undergo along the inner medullary collecting duct?
What percentage does urea contribute to the total inner medullary interstitial fluid osmolality?
What percentage does urea contribute to the total inner medullary interstitial fluid osmolality?
What is the process of passive countercurrent multiplication by the thin ascending limb of the loop of Henle?
What is the process of passive countercurrent multiplication by the thin ascending limb of the loop of Henle?
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Study Notes
Loop of Henle Overview
- The loop of Henle reabsorbs approximately 25% of filtered NaCl and water, playing a crucial role in urine concentration and dilution.
- It consists of three segments: thin descending limb, thin ascending limb, and thick ascending limb, each with unique transport and permeability characteristics.
Ascending Limb Functions
- The ascending limb absorbs 25% of sodium through the Na+-K+-2Cl- cotransporter located in the luminal membrane.
- It serves as a diluting segment, impermeable to water but capable of reabsorbing NaCl, thereby reducing tubular Na+ concentration and osmolarity.
Diuretics Mechanism
- Loop diuretics, such as furosemide, inhibit the Na+-K+-2Cl- cotransporter in the luminal membrane, significantly increasing urine flow and sodium excretion.
- Thiazide diuretics act on the early distal tubule, impairing sodium reabsorption via the Na+-Cl- co-transporter.
Concentration Gradients
- The thick ascending limb's basolateral membrane channels sodium out, creating a concentration gradient that facilitates sodium entry from the apical membrane.
- A hyperosmotic interstitial fluid is generated in the outer and inner medulla, aided by NaCl reabsorption.
Countercurrent Mechanism
- The countercurrent mechanism enables the production of concentrated urine by facilitating the exchange of solutes and water in opposing directions within the nephron.
- As dilute urine ascends through the thick ascending limb, antidiuretic hormone (ADH) acts to concentrate urine in the late distal tubule and collecting duct.
Urea Reabsorption
- After glomerular filtration, 50% of urea is reabsorbed in the proximal tubule, with additional reabsorption occurring in the inner medulla.
- ADH promotes urear reabsorption in the inner medullary collecting duct through passive diffusion, contributing to the osmotic gradient necessary for water reabsorption.
Role of Urea
- Urea recycling contributes approximately 40% to the total osmolality of the inner medullary interstitial fluid, enhancing the passive countercurrent multiplication process and promoting additional solute reabsorption.
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