Lecture 8- Concentration And Dilution

Question 1

What does medullary thickness do to an animal’s kidney function

Answer 1

Increases ability to concentrate urine

Question 2

Countercurrent multiplication in loop of henle

Answer 2

Produces concentration gradient that is most dilute in the tip of loop of henle

In the thick ascending limb (impermeable to water, permeable to ions), Na is actively transported into the interstitium

This causes water from the descending limb (permeable to water, impermeable to ions) to passively go to interstitium

Question 3

Permeability of proximal tubule

Answer 3

Permeable to salts and water

Question 4

Permeability of descending loop of henle

Answer 4

Permeable to water

Impermeable to salt

Question 5

Permeability of ascending loop of henle

Answer 5

Permeable to salt

Impermeable to water

Question 6

Permeability of distal tubule and collecting duct

Answer 6

Presence of ADH- permeable to water

No ADH- impermeable to water

Question 7

How does vasa recta help the countercurrent multiplication

Answer 7

The arrangement of the vasa recta allows for solutes to remain in the medulla instead of being washed out by blood flow. This helps maintain the concentration gradient of the medulla.

Solutes move from collecting duct and loop of henle into vasa recta. Solutes move from ascending vasa recta to descending vasa recta

Question 8

How is urea transported

Answer 8

Passive diffusion

Question 9

Is urea reabsorbed or secreted

Answer 9

Net reabsorption in proximal tubule and collecting duct

Net secretion in loop of henle

Question 10

Why is urea recycled

Answer 10

Helps establish medullary osmotic gradient with less energy expenditure and conserve water

Question 11

How is urea transport controlled in the collecting duct?

Answer 11

ADH controls urea transport in collecting duct

In the inner medulla, ADH only makes the collecting duct permeable to urea instead of water. This allows urea to contribute to the osmolality gradient of the medulla