Physiology 4+5: Proximal tubule and Loop of Henle

Question 1

what % of urea is reabsorbed by the kidney tubules

Answer 1

50%

Question 2

what % of creatinine is reabsorbed by the kidney tubules

Answer 2

0%

Question 3

what % of fluid, salt, glucose and amino acids are reabsorbed by the kidney tubules

Answer 3

fluid + salt = 99% / glucose + amino acids = 100%

Question 4

what does the glomerular filtrate contain

Answer 4

ions and solutes but no RBC’s or plasma proteins

Question 5

what osmolarity is the filtrate when it enters AND leaves the proximal tubule

Answer 5

iso-osmotic at 300mosmol/l

Question 6

what % of substances are reabsorbed in the proximal tubule PT

Answer 6

66% of sodium and water

Question 7

what substances are reabsorbed in the PT (7)

Answer 7

sugar, amino acids, phosphate, sulphate, lactate, water, potassium

Question 8

what substances are secreted in the PT (6)

Answer 8

H+, neurotransmitters, bile, drugs, toxins, hippurates

Question 9

what 2 ways can substances be reabsorbed from the tubules

Answer 9

transcellular or paracellular

Question 10

what is primary active transport

Answer 10

energy directly required to carry against a concentration gradient

Question 11

what is secondary active transport

Answer 11

transport is coupled to concentration gradient of an ion (usually Na)

Question 12

what is facilitated diffusion

Answer 12

passive transport down a concentration gradient with a transporter

Question 13

how is Na reabsorbed from the lumen into the tubular epithelial cell in the PT (3)

Answer 13

cotransport with glucose and amino acids and also counterport (anti port) with H+ being secreted into the lumen

Question 14

hows Na transported from the tubular epithelial cell to the per tubular capillaries in the PT

Answer 14

via NaKATPase at the basolateral membrane (3Na out and 2 K in)

Question 15

how does the reabsorption of Na also drive H20 and Cl reabsorption

Answer 15

standing osmotic gradient where water follows sodium by water and the oncotic drag of the peritubular plasma

Question 16

how is glucose reabsorbed in the PT

Answer 16

con transport with Na out of lumen and then facilitated diffusion at basolateral membrane

Question 17

when does glucose reabsorption stop in the PT

Answer 17

at the transport maximum when all the cotransporters are fully saturated - 2 mol/min

Question 18

what is the function of the loop of henle

Answer 18

generates portico-medullary solute concentration gradient to create concentrated urine

Question 19

how is countercurrent flow created in the loop of Henle

Answer 19

descending (first) and ascending (second) limb travel in opposite direction

Question 20

what does the ascending limb (2nd) loop of henle reabsorb

Answer 20

Na and Cl - very little/ no water follows

Question 21

what is the difference between transport in the thick upper part of the ascending limb and the lower thinner part

Answer 21

upper part is active transport and lower part is passive

Question 22

what does the descending limb (1st) of the loop of Henle reabsorb

Answer 22

water - no active salt reabosrption

Question 23

how is Na and Cl reabsorbed in the thick ascending loop of henle

Answer 23

triple-cotransporter of K, Na and Cl called TALH (K then leaks back into lumen filtrate)

Question 24

1) Solute is removed from the lumen in the ______ limb and ____ cannot follow, making the filtrate ___tonic with a ___ osmolarity

Answer 24

ascending, water, hypo, low (it is diluted)

Question 25

2) Tubular fluid becomes diluted and causes the interstitial fluid between the ascending and descending limb to become ___ tonic as the solute cannot renter the tubules

Answer 25

hyper (is concentrated)

Question 26

3)due to the high osmolarity in the interstitial ___ leaves the ____ limb by ___

Answer 26

water, descending, osmosis, greater

Question 27

4) the tubular fluid in the descending limb becomes ___tonic and has a ___ osmolarity due to water following it’s concentration gradient and leaving the filtrate

Answer 27

hyper, high (concentrated)

Question 28

5) what happens to the water after it has diffused out the descending limb into the hypertonic interstitium

Answer 28

it is reabsorbed into capillaries

Question 29

how does the urea cycle affect the medullary osmolarity

Answer 29

adds solute to the interstitial which adds to the medullary osmolarity

Question 30

in the loop of Henle, which is a larger gradient vertical or horizontal?

Answer 30

vertical

Question 31

why is the counter current multiplication in the loop of henle useful in regards to ADH levels

Answer 31

kidneys can still produce concentrated urine despite varying ADH levels

Question 32

what is the vasa recta

Answer 32

arterioles and venules that run the length of the kidney

Question 33

what is the purpose of the vasa recta

Answer 33

water and solute is absorbed into the blood supply instead of being washed away in the medulla