urology and renal

Question 1

what is osmotic pressure proportional to?

Answer 1

number of solute particles

Question 2

how is osmolarity calculated?

Answer 2

concentration x no. of dissociated particles

Question 3

how is body fluid distributed?

Answer 3

2/3 intracellular fluid

1/3 extracellular fluid

Question 4

how is extracellular fluid distributed?

Answer 4

3/4 extravascular

• 95% interstitial fluid
• 5% transcellular fluid (e.g. CSF)

1/4 intravascular (plasma)

Question 5

what divides extracellular fluid and intracellular fluid?

Answer 5

cell membrane

Question 6

what divides extravascular fluid and intravascular fluid?

Answer 6

capillary wall

Question 7

how is water lost (unregulated)?

Answer 7

sweat

faeces

vomit

water evaporation from respiratory lining and skin

Question 8

how is water lost (regulated)?

Answer 8

renal regulation – urine production

Question 9

what are the 2 types of renal regulation?

Answer 9

positive water balance

negative water balance

Question 10

what is the process of positive water balance?

Answer 10

high water intake

increased extracellular fluid volume, therefore decreased [Na+]

decreased osmolarity

hypoosmotic urine produced (lose excess water)

osmolarity normalised

Question 11

what is the process of negative water balance?

Answer 11

low water intake

decreased extracellular fluid volume, therefore increased [Na+]

increased osmolarity

hyperosmotic urine produced (conserve water)

osmolarity normalised

Question 12

how is water reabsorbed in the kidneys?

Answer 12

mostly reabsorbed in PCT

passive movement out of descending limb of loop of Henle (no movement of ions)

active and passive transport of ions out of ascending limb in loop of Henle (no movement of water out)

variable water reabsorption in collecting duct

Question 13

what is necessary for reabsorption of water in the loop of Henle and collecting duct?

Answer 13

medullary interstitium needs to be hyperosmotic

Question 14

how is hyperosmotic medullary interstitium created?

Answer 14

countercurrent multiplication

Question 15

what is the process of countercurrent multiplication?

Answer 15

both descending and ascending limb have equal osmolarity

active salt reabsorption - osmolarity decreases in ascending limb and increases in medullary interstitium

passive water reabsorption from descending limb increases osmolarity

filtrate keeps entering - eventually osmolarity increases going down descending limb, decreases going up ascending limb (creates gradient)