Lecture 36: Urinary 5

Question 1

What is glomerular filtration rate?

How is this measured?

Answer 1

GFR = is the volume of fluid that is filtered from the glomerular capillaries into the Bowman’s capsule in a period of time .GFR = 125ml/min or 180L/day
GFR = V x U / P
creatine is used to estimate GFR

Question 2

What is glomerular clearance?

Answer 2

Clearance: gives a measure of how much of a particular substance is being ‘cleared’ by the kidneys
Clearance = U x V / P

Question 3

What is filtration fraction?

What is filtered load?

Answer 3

Filtered fraction: is the fraction of renal plasma flow (RPF) that is being filtered
Filtered fraction = GFR / RPF

The filtered load is the amount of a particular substance that is filtered in a minute
Filtered load = GFR x solute plasma conc

Question 4

How is renal blood flow regulated ?

Answer 4

Intrinsic mechanisms

Extrinsic mechanisms

Question 5

How is renal blood flow regulated through intrinsic mechanisms?

Answer 5

• MYOGENIC = the vascular smooth muscles of the afferent arteriole in the kidneys constricts or dilates in response to changes in blood pressure
  TUBULOGLOMERULAR feed back = the macula dense cells of the juxtaglomerular apparatus sense the chemical composition of the urine and alter renal blood flow

Question 6

How is renal blood flow regulated though extrinsic mechanisms?

Answer 6

• Sympathetic nervous system ; causes vasoconstriction

- Angiotensin II causes vasoconstriction

Question 7

What is hydrostatic pressure ?

What is osmotic pressure ?

Answer 7

• is the pressure exerted by a fluid

- is a pressure that depends on the concentrations of solutes present in solutions either side of the membrane

Question 8

What is glomerular filtration determined by ?

Answer 8

• Forces/gradient btw glomerular capillary & bowman’s space
• Permeability of glomerular capillary
• Surface area of glomerular capillary

Question 9

Effective filtration pressure

- what forces are involved if we want to move fluids OUT of the glomerulus ?

Answer 9

• Glomerular hydrostatic pressure

- Capsular osmotic pressure

Question 10

Effective filtration pressure

- what forces are involved if we want to move fluids INTO the glomerulus ?

Answer 10

• Glomerular osmotic pressure

- Capsular hydrostatic pressure