Loop of henle

Question 1

Site of major reabsorption of NaCl, water

Answer 1

Proximal tubule

Question 2

What protein gets filtered out and what happens to it

Answer 2

Albumin

Completely reabsorbed by a Tm(subscript) carrier mechanism in the proximal tubule

Question 3

Why are drugs and pollutants hard to get rid of

Answer 3

Many are non-polar so very lipid soluble

So the removal of water in the proximal tubule establishes concentration gradients for their reabsorption.

Question 4

How do we get rid of drugs and pollutants

Answer 4

The liver metabolizes them to polar compounds thus reducing their permeability and facilitating their excretion.

Question 5

Where are the proximal and distal tubules of the nephrons

Answer 5

In the cortex

Question 6

What is responsible for water balance

Answer 6

Loops of henle in juxtamedullary nephrons

Question 7

What do loops of henle in juxtamedullary nephrons allow us to do

Answer 7

Produce concentrated urine in times of water deficit

Question 8

Minimum obligatory loss of water in urine per day

Answer 8

500ml

Question 9

What do loops of henle in juxtamedullary nephrons act as

Answer 9

counter-current multipliers.

Question 10

What does counter-current mean

Answer 10

Fluid flows down descending limb and up ascending limb

Question 11

What makes the loops counter-current multipliers

Answer 11

The ascending limb, which is impermeable to water, actively co-transports Na+ and Cl- ions out of the tubule into the interstitium.

The descending limb is freely permeable to H2O but relatively impermeable to NaCl.

Question 12

What value is isosmotic with plasma

Answer 12

300mOsm/l

Question 13

What happens to NaCl in the ascending limb and when does it stop

Answer 13

It is pumped out until a gradient of 200mOsm/l is achieved

Question 14

What happens to the osmolarity of the ascending limb and to the interstitium

Answer 14

Ascending limb = decreases

Interstitium = increases

Question 15

What happens to the descending limb and why

Answer 15

Water moves into interstitium

Because the descending limb is exposed to a greater osmolarity so water moves to equate the osmolarity

Question 16

What happens to the water after it leaves the descending limb

Answer 16

It moves into the vasa recta

Question 17

What is the change in the vertical gradient of the interstitium

Answer 17

300-1200 mOsm/l

Question 18

What is the key step in creating the concentration gradient and what drug can impair it

Answer 18

The active transport of NaCl

Furosemide (loop diuretic)

Question 19

How does fluid in the distal tubule compare to plasma concentration wise

Answer 19

It is more dilute than plasma

Question 20

Fluid enters the counter-current multipliers at what concentration and leaves at what concentration

Answer 20

Enters = 300 mOsm/l

Leaves at 100mOsm/l

Question 21

What is the juxtamedullary nephron all about

Answer 21

concentrating the medullary interstitium

And delivering hypotonic fluid to the distal tubule.

Question 22

Three functions of the vasa recta

Answer 22

Provide O2 for medulla
In providing O2 MUST NOT DISTURB GRADIENT
Removes volume from the interstitium

Question 23

What’s the flow rate like in the vasa recta and why

Answer 23

Very low

Allows plenty of time equilibration to occur in the interstitium

Question 24

Site of water regulation and by what hormone is it controlled by

Answer 24

The collecting Duct

ADH (controls permeability of collecting duct)