Loop Of Henle

Question 1

Urine entering loop of henle

Answer 1

Isotonic

Question 2

Function of loop of henle

Answer 2

Concentrates urine by creating a region of hypertonicity to extract the water osmotically
More Na+ reabsorption
Urinary dilution
Generation of medullary hyperosmoticity via counter-current multiplication

Question 3

Descending limb

Answer 3

Water permeable
Impermeable to solutes

Question 4

Ascending limb

Answer 4

Impermeable to water
Permeable to solutes

Question 5

Counter-current multiplication

Answer 5

Urinary concentration and generation of hyperosmotic interstitium to aid collecting duct in water reabsorption

Question 6

Thick ascending limb driving force

Answer 6

Na/K ATPase in basolateral membranes of cells in ascending limb which keep intracellular Na+ concentrations low to allow more reuptake

Question 7

Which transporter pumps Na+ out of lumen of Thick ascending limb

Answer 7

NKCC2 via secondary active transport

Question 8

Thick ascending limb - K+

Answer 8

Recycled on apical ,membrane back into lumen through ROMK channels

Question 9

Thick ascending limb K+channels on apical membrane

Answer 9

ROMK

Question 10

Thick ascending limb Cl-

Answer 10

Leaves cell through CLCK A channels on basolateral membrane

Question 11

Where are CLCK B channels found

Answer 11

Inner medulla

Question 12

Thick ascending limb Ca2+, Mg2+ and Na+

Answer 12

Process of counter current multiplication creates a negatively charged tubule lumen which repels Ca2+, Mg2+ and Na+ and they move paracellularly with the aid of proteins in the tight junctions (paracelin or claudin XVI)

Question 13

Proteins in tight junctions of Thick ascending limb

Answer 13

Paracelin
Claudin XVI

Question 14

Function of Thick ascending limb

Answer 14

Creates hyperosmotic interstitium, creates a gradient of 200mOsm/L between lumen and interstitium

Question 15

Gradient between lumen and interstitium

Answer 15

200 mOsm /L

Question 16

Thin ascending limb

Answer 16

Salt pumped passively

Question 17

Descending limb

Answer 17

Only permeable to water which flows out due to osmotic pressure, concentration of interstitium matches concentration in descending limb

Question 18

As fluid moves down descending limb

Answer 18

Becomes more concentrated- the longer the loop the greater the gradient which is created
Tubule flow means that the concentration gradient starts from a higher baseline than before it

Question 19

What ions does the ascending limb pump out

Answer 19

Na+
K+
Cl-

Question 20

Urea involvement

Answer 20

Vasopressin makes collecting duct permeable to urea so it leaks into interstitium- which aids urine concentration in loop of henle
As urea passes through the remainder of the nephron it is reabsorbed, secreted into the tubule and then reabsorbed again

Question 21

What supplies blood to the loop of henle

Answer 21

Vasa recta

Question 22

Medullary circulation

Answer 22

Vasa recta prevent elimination of counter current gradient
As blood ,over down it meets an increasingly hypertonic environment drawing water out of the blood vessel into the interstitium (concentrating the blood)- blood has a high oncotic pressure as proteins not filtered
Crossing pathways protect the concentration gradient at each level and bulk flow carries away salts and water reabsorbed
Blood enters the top of the vessel loop and as it flows down into the medulla, Na+ and Cl- flow in and water out
After the bend in the loop the blood ascends and the process is reversed

Question 23

Advantage of loop structure

Answer 23

Minimises excessive loss of solute from interstitium by diffusion into vasa recta

Question 24

Volume of blood before and after loop of henle

Answer 24

At least 2 fold higher due to salt and water reabsorption

Question 25

Why doesn’t blood flow wash out the osmotic gradient

Answer 25

Vasa recta
Long capillaries extend into medulla
Permeable to solute and water

Question 26

Transporters in apical membrane

Answer 26

NKCC2
ROMK

Question 27

Transporters on basolateral membrane

Answer 27

Cl-
Na/K ATPase