Loop of Henle, Distal Tubule and collecting duct

Question 1

Function of Thin descending loop of henle?

Answer 1

Starts at the distal end of proximal tube and runs to outer medulla. Hyperosmolar. Very permeable to water. No active transport. Minimal permeability to urea and NaCl. Water leaves.

Question 2

Difference between thin descending loop and thin ascending limb?

Answer 2

The transport properties of the two are dramatically different. Thin ascending limb is practically impermeable to water and urea. Very permable to NaCl. This is where most NaCl reabsorption takes place. Osmolarity goes down

Question 3

What are the characteristics of the thick ascending limb?

Answer 3

Thick epithelial cells with many mitochondria. Like the thin ascending limb, it is impermeable to water. Strong NaCl reabsorption. Three major transporters

Question 4

What are the three major transporters of the thick ascending limb?

Answer 4

Na-K-ATPase, Na-K-2Cl (NK2C) , other channels like basolateral Cl channel etc…

Question 5

What is the most regulated channel in the thick ascending limb?

Answer 5

NK2C….diuretics work on this transporter by blocking the Cl site and blocking NaCl reabsorption. This increases NaCl load to the distal nephron and brings with it more fluid leading to water loss.

Question 6

Distal convoluted tubule characteristics?

Answer 6

Formed by 6-8 collecting ducts. Na is actively reabsorbed, K is secreted, Na absorption is greater than K secretion therefore Cl is reabsorbed. Ultimately results in dilution of tubular fluid. Water permeability fluctuates, in diuresis its impermeable. In dehydration, its permeable

Question 7

Two channels in the collecting duct?

Answer 7

1. ) Electrically conductive Na channels- Na enters cells from the lumen and is powered by the electrochemical gradient created by Na-K-ATPase pump which is pumping Na out to the interstitium
2. ) Na- Cl- co transporter

Question 8

What drives potassium secretion out of DCT and CD epithelial cells and where does it go?

Answer 8

Potassium moves back into the lumen. Driven by high intracellular K concentration and negative charge of the lumen.

Question 9

Increaed fluid flow, cuased by things like diuretics, does what to the potassium secretion?

Answer 9

Increases potassium secretion