Physiology of the kidney

Question 1

what percentage of the total blood pumped by the heart goes to the kidneys

Answer 1

20%

Question 2

in one day how many litres of blood is purified and how much urine is produced

Answer 2

1700 litres purified

1.5-2 litres of urine

Question 3

how many litres of blood do adults have and how many times a day is it filtered

Answer 3

7-8 litres and 400 times a day

Question 4

what is the measurement of normal kidney function

Answer 4

100-120 mls/min/1.73m^2

Question 5

what is the radioactive tracer injection into kidneys to assess function

Answer 5

technetium Tc99

Question 6

what is the amount of creatinine clearance used to estimate

Answer 6

rate of glomerular filtration

Question 7

where is serum creatinine released from

Answer 7

muscle

Question 8

what are the normal blood test levels for creatinine in males and females

Answer 8

males = 64-102 micromol/L
females = 60-93 micromol/L

Question 9

what is used instead of creatinine clearance and what is used to calculate it

Answer 9

estimated glomerular filtration rate

age, sex, ethnicity, serum creatinine

Question 10

what would an eGFR of 50 mean

Answer 10

50% kidney function

Question 11

what is the relationship between creatinine clearance and eGFR

Answer 11

Creatinine clearance ( CrCl ) is an estimate of Glomerular Filtration Rate ( GFR ); however, CrCl is slightly higher than true GFR because creatinine is secreted by the proximal tubule (in addition to being filtered by the glomerulus). The additional proximal tubule secretion falsely elevates the CrCl estimate of GFR

Question 12

in the proximal convoluted table what happens to molecules and which in particular

Answer 12

recovers 70% of glomerular filtrate 
water
electrolytes 
glucose 
amino acids 
recovery and generation of bicarbonate

Question 13

what is the reabsorption of bicarbonate dependant on in the PCT

Answer 13

carbonic anhydrase

Question 14

what happens if there is a problem in the PCT

Answer 14

failure to reabsorb bicarbonate and metabolic acidosis

Question 15

describe the process of absorption of bicarbonate in the PCT

Answer 15

check photos

Question 16

what molecules are taken up in the ascending limb of the Henle

Answer 16

Na+
K+
2Cl-
H20

Question 17

describe the mechanism of absorption of molecules in the ascending limb

Answer 17

check photos

Question 18

what occurs in the cortical collecting duct and what controls this process

Answer 18

site of reabsorption of Na+ (with h20 and cl) in exchange for K+
controlled by aldosterone

Question 19

what occurs in the medullary collecting duct and what is it controlled by

Answer 19

site of urinary concentration

ADH acts to increase water absorption ie less urine

Question 20

what is the plasma osmolality maintained at

Answer 20

285 mOsm/L - optimal for cellular function

Question 21

what is the normal urine osmolality

Answer 21

50-1400 mOsm/L

Question 22

what is the osmolality of dilute vs concentrated urine

Answer 22

dilute = 50 mOsm/L

dark yellow = 1400 most/L

Question 23

what are some ways in which we lose fluids

Answer 23

sweating
faeces
respiration
urine

Question 24

what does the renin angiotensin / aldosterone system allow

Answer 24

vasoconstriction and increase Na reabsorption which means more water retention