Loop of Henle Flashcards

Questions and Answers

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?

Na+-K+-2Cl- cotransporter in luminal membrane

Loop diuretics inhibit:

Na+-K+-2Cl- cotransporter in luminal membrane

What is the diluting segment in the ascending loop of Henle?

It is a region impermeable to water, however, NaCl is reabsorbed here without water. Signup and view all the answers

Distal tubule reabsorbs sodium via what co-transporter?

Na+-Cl- Signup and view all the answers

Where do thiazide diuretics inflict their damage?

Early distal tubule Signup and view all the answers

What is the role of the loop of Henle?

Responsible for reabsorbing approximately 25% of the filtered NaCl and water. Signup and view all the answers

What are the different segments of the loop of Henle?

Thin descending limb, thin ascending limb, thick ascending limb Signup and view all the answers

What is the thin descending limb most permeable to?

Water, solutes (NaCl, urea), little to no active NaCl transport Signup and view all the answers

The thin ascending limb of Loop of Henle is permeable to?

Impermeable to H2O; permeable to solutes and active transport to NaCl Signup and view all the answers

What is the importance of the basolateral membrane channeling sodium out of the cell in the thick ascending loop of Henle?

Loss of NaCl creates a concentration gradient. Signup and view all the answers

What apical membrane cotransporter system is targeted by high-ceiling diuretics?

Na+/K+/2Cl- cotransporter Signup and view all the answers

What percentage of sodium is reabsorbed by the thick ascending limb of Henle via the paracellular pathway?

50% Signup and view all the answers

Why is the thick ascending limb considered to be the diluting segment?

It reabsorbs NaCl while not adding water. Signup and view all the answers

Compare the transfer of NaCl in the thick ascending loop of Henle and the early distal convoluted tubule.

NaCl enters via Na+/K+/2Cl- cotransporter in thick ascending limb; apical NaCl co-transporter in early distal tubule. Signup and view all the answers

NaCl is reabsorbed by the thick limb of the loop of Henle via what transport mechanism?

Active transport; co-transport K+-Na+-2Cl- Signup and view all the answers

What is the countercurrent mechanism/system?

The process by which a hyperosmotic urine is produced. Signup and view all the answers

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?

In the outer and inner medulla. Signup and view all the answers

As the dilute urine passes up through the thick ascending loop of Henle, what hormone functions to concentrate urine?

Antidiuretic Hormone Signup and view all the answers

What allows water to leave the tubular lumen into the interstitial fluid?

Osmotic gradient present. Signup and view all the answers

What percentage of urea is filtered in the glomerulus and reabsorbed by the proximal tubule?

50% Signup and view all the answers

After the proximal tubule reabsorption, where does urea reabsorption occur again?

Inner medulla Signup and view all the answers

ADH permits urea reabsorption in what region of the kidney?

Inner medullary collecting duct Signup and view all the answers

What type of transport does urea undergo along the inner medullary collecting duct?

Passive diffusion due to high levels of urea. Signup and view all the answers

What percentage does urea contribute to the total inner medullary interstitial fluid osmolality?

40% Signup and view all the answers

What is the process of passive countercurrent multiplication by the thin ascending limb of the loop of Henle?

<ol> <li>Provides gradient for NaCl reabsorption; 2) Urea reabsorbed into medullary interstitium.</li> </ol> Signup and view all the answers

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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Description

Test your knowledge on the Loop of Henle with these flashcards. Each card covers key facts, including sodium absorption and the mechanisms involved. Ideal for students studying renal physiology.