urine formation 2

Question 1

what are the 3 basic processes of urine formation?

Answer 1

glomerular filtration
tubular secretion and tubular reabsorption.

Question 2

what produces glomerular filtrate?

Answer 2

blood pressure forces water and most solutes in blood plasma towards walls of glomerular capillaries, producing glomerular filtrate.

Question 3

what 3 pressure does glomerular filtration depend on?

Answer 3

1) glomerular blood hydrostatic pressure (HP)promotes filtration
2) capsular HP (opposes filtration),
3) blood colloidal osmotic pressure (BCOP), due to proteins in plasma (opposes)

Question 4

does afferent or efferent arteriole have higher resistance and increases BP upstream in glomerulus?

Answer 4

Efferent arteriole.

Question 5

where are mesangial cells positioned?

Answer 5

between capillaries.

Question 6

mesangial cells (intraglomerular) do what?

Answer 6

decrease surface area of capillaries so glomerular filtration decreases.

Question 7

what is globular filtration rate defined as (GFR)?

Answer 7

amount of filtrate formed in all renal corpuscles of both kidneys each minute. 105/125/min. female/male

Question 8

150-180 L/ day of filtration but since 99% is returned to blood, how much is actually excreted?

Answer 8

1-2 litres.

Question 9

what keeps GFR relatively constant by renal autneural and hormone regulation ?

Answer 9

Homeostasis.

Question 10

What do severe blood loss and High blood pressure do to GFR?

Answer 10

Severe blood loss - decreases GFR
high blood pressure - doesn’t increase much

Question 11

what does atrial natriuretic peptide (ANP) do?

Answer 11

It opposes the renin-angiotensin system.

Question 12

Net filtration pressure =

Answer 12

Glomerular blood hydrostatic pressure - capsular HP- blood colloidal osmotic pressure.

Question 13

Describe the chain that happens when glomerular capillaries become damaged/pereable

Answer 13

Plasma proteins enter glomerular filtrate, leads to
Decreased BCOPressure, leads to
H2O drawn out of blood, leads to
Increased Net FP, leads to
Decreased blood volume & increased interstitial fluid volume, leads to
Oedema

Question 14

what happens during tubular reabsorption?

Answer 14

filtered fluid flows along the renal tubule and through the collecting duct.
Tubule and duct cells return 99% of filtered water and useful solutes to blood flow through peritubular capillaries.

Question 15

How do tubule and duct cells return 99% of filtered water and solutes to blood flow?

Answer 15

through peritubular capillaries.

Question 16

Tubular reabsorption goes through what process to reclaim back into blood?

Answer 16

selective process.

Question 17

In tubular reabsorption, transport across membranes may be one of 3…

Answer 17

-Active 1 - uses ATP, Na+, bicarbonate ions (stabilises blood pH).
-Active 2- uses ion’s electrochemical gradient, glucose , AAs
-Passive, urea, lipid soluble non polar components, H2O

Question 18

What does ‘transport maximum Tm’ do?

Answer 18

it reflects number of carriers available to transport substance (except Na+).

Question 19

What happens during tubular secretion?

Answer 19

Tubule and duct cells remove substances from the blood in the peritubular capillaries and transports them into the fluid in the renal tubules, eg wastes, drugs (penicillin , morphine) and excess ions.

Question 20

What is tubular secretion a backup for?

Answer 20

for the material not filtered out in the glomerulus.

Question 21

There is hormonal regulation for what processes of urine formation?

Answer 21

tubular reabsorption and secretion.

Question 22

how to determine the rate of urinary excretion of any solute.

Answer 22

rate of glomerular filtration - rate of reabsorption + rate of secretion.

Question 23

which is excreted more, glucose or urea?

Answer 23

Urea.

Question 24

if the filtration- reabsorption - secretion is disrupted , is it fatal?

Answer 24

Yes, you can die.

Question 25

What controls production of dilute and concentrated urine?

Answer 25

antidiuretic hormone - ADH,also called vasopressin.

Question 26

What is the Osm/kg of dilute and concentrated urine?

Answer 26

dilute urine - 65 Osm/kg
concentrated urine - 1200Osm/kg
extracellular urine - 300Osm/kg

Question 27

What happens if antidiuretic hormone (ADH) is absent from urine production?

Answer 27

Urine will contain high ratio of water to solutes (dilute urine), as principal cells of collecting duct are impermeable to water.

Question 28

What happens if antidiuretic hormone (ADH) is present in urine production?

Answer 28

water is reabsorbed back into blood (concentrated urine) due to osmotic gradient maintained by :
1) differences in solute & water permeability
2)countercurrent flow.

Question 29

If too little water in blood, how does the body return to normal?

Answer 29

1) hypothalamus detects little water in blood
2) pituitary gland releases ADH
3) kidneys maintain blood water level
4) so less water is lost in urine (urine more concentrated)
5) blood water levels return to normal