Generation of Medullary Hypertonicity

Question 1

What is the loop of henle?

Answer 1

A renal paradox

Question 2

What 2 types of creatures can concentrate urine?

Answer 2

Mammals and birds

Question 3

What 2 types of creatures have loops of henle?

Answer 3

Mammals and birds

Question 4

What is the loop vital for?

Answer 4

concentrating ability

Question 5

What happens to the fluid leaving the loop compared to plasma?

Answer 5

Is dilute

Question 6

What is medullary hypertonicity generated by?

Answer 6

Countercurrent multiplication of loops of henle, distal tubules and collecting ducts

Question 7

What is handled in the collecting ducts?

Answer 7

Facultative water ADH

Question 8

How is medullary hypertonicity generated?

Answer 8

Different H2O permeabilities - DL is permeable, AL is not
Ability of TAL to extrude NA to medullary interstitium - basolateral NaK ATPase
Transverse osmotic gradient - 200mosmol, for large longitudinal gradient

Question 9

what does a 200 mosmol H2O difference between AL and DL create?

Answer 9

Small transverse osmotic gradient

Question 10

how does countercurrent multiplication work?

Answer 10

Multiplied into longitudinal gradient - counterflow of tubular fluid as result of hairpin bend in loop

Question 11

What is facultative H20 handle according to?

Answer 11

DCT and collecting ducts

Question 12

What are the 2 sections of the collecting duct?

Answer 12

Cortical collecting duct CCD

Medullary collecting duct MCD

Question 13

What is the DCT,CCD,MCD impermeable to?

Answer 13

H2O,UREA,NaCl

Question 14

What does anti-diuretic hormone ADH do?

Answer 14

Increase H2o permeability of the segments DCT,CCD,MCD according to need

Question 15

What happens in the cortical CD with ADH?

Answer 15

Increased h2o reabsorption - fluid osmolality increases from 90 to 290 mosmol

Question 16

What happens to the remaining fluid in presence of ADH?

Answer 16

5% of total glomerular filtrate, enters medullary CD for more H2o reabsorption

Question 17

What would too much reabsoprtion in the medulla cause?

Answer 17

Medullary hypertonicity

Question 18

Where does more H2O reabsorption take place?

Answer 18

Cortical CD

Question 19

Where is Urea freely filtered?

Answer 19

Glomerulus

Question 20

How and how much urea reabsorped in PCT?

Answer 20

50% passively reabsorbed

Question 21

Where does Urea conc increase in DL to?

Answer 21

Along loop to passive diffusion from interstitium

Question 22

What is impermeable to urea?

Answer 22

DCT, Cortical CD

Question 23

What is permeable to H20 ADH?

Answer 23

DCT, cortical CD

Question 24

What happens when H2o leaves cortical CD?

Answer 24

Urea conc rises

Question 25

What does ADH activate?

Answer 25

urea uniporter in medullary CD

Question 26

Where does Urea diffuse?

Answer 26

Along gradient from medullary CD to interstitium into TAL//DL

Question 27

Where does Urea travel along tubule to?

Answer 27

DC/Cortical CD - cycle repeats

Question 28

What area has high urea conc?

Answer 28

Interstitium

Question 29

What is 50% of medullary hypertonicity due to?

Answer 29

urea recycling

Question 30

What percentage of nephrons are Juxtamedullary long?

Answer 30

15%

Question 31

What percentage of nephrons are cortical short?

Answer 31

85%

Question 32

Where do all nephrons drain into?

Answer 32

Collecting ducts which pass through the medulla - possible to gain conc of urine from all nephrons