La concentration et la dilution de l'urine

Question 1

Where does the Anse de Henle start and where does it end?

Answer 1

Start: right after proximal convoluted

End: right before macula densa

Question 2

What are the 4 segments of the Anse de Henle?

Answer 2

1. branche grêle descendante
2. branche grêle ascendante
3. branche large medullaire
4. branche large ascendante corticale

Question 3

What are the two functions of the Anse de Henle?

Answer 3

1. reabsorption of 15-20% of filtered NaCl
2. reabsorption of more NaCl than water… non isoosmotique

Question 4

When is the loop permeable and impermeable to water?

Answer 4

Permeable when its descending and impermeable when it’s going back up (except for tubule collecteur in the presence of ADH)

Question 5

Cells of large ascending:

Answer 5

lots of mitochondria in the replis baso-latéraux

Question 6

How are the cells of the large assending the principal actor of the anse de Henle?

Answer 6

very metabolically active —> responsible for active transport of NaCl towards the interstitium of the medulla where salt will accumulate and cause the hypotonicity of the medulla which is crucial for concentration and dilution of urine

• it is considered the motor of the anse… if its not working properly, we wouldnt be able to properly dilute or concentrate our urine

Question 7

What is the principal motor of the tubule?

Answer 7

Na-K ATPase

Question 8

What is the physiological problem with drinking water?

Answer 8

Le rein doit suivre la bouche MAIS l’ingestion d’eau est variable

• therefore the kidneys must be able to change the concentration of your using quite easily

Question 9

How does the counter current work?

Answer 9

Responsible for the generation of the hypotonic medulla which is essential to concentrate/dilute urine

Question 10

What happens when you need concentrated urine?

Answer 10

Liquid that leaves proximal tubule is isoosmotic with the plasma but this is not adequate to maintain homeostasis

Question 11

What are the two steps that need to happen in order to excrete concentrated urine (if dehydrated)?

Answer 11

1. interstitium médullaire is hyperosmotic due to reabsoprtion of NaCl in large ascending branch of Henle and urea that enters interstitium from the tubule collecteur médullaire
2. ADH is secreted which increases the permeability of the tubule collecteur to water which allows transcellular reabsorption of water through inserted aquaporins

Question 12

What are the two important supplementary factors that allow for maintaining medullary hyperosmolality?

Answer 12

1. reabsorption of water is induced in the tubule collecteur cortical to diminish water entry in the medulla
2. medullary blood flow in the vasa-recta happens using a counter current as well to minimize reabsorption of interstitial solutes

Question 13

What are the two steps that need to happen in order to excrete diluted urine?

Answer 13

1. reabsorption of NaCl without water in the large ascending branch which decreases the osmolality of liquide tubaire while increasing the osmolality of the interstitium
2. urine stays diluted because the tubule collecteur is impermeable to water without the presence of ADH