Lecture 32: Glomerular function

Question 1

Filtration is a specific form of what?

Answer 1

Ultrafiltration

Question 2

What is ultrafiltration?

Answer 2

Filtration on a micro scale

Question 3

Filtration creates what?

Answer 3

A plasma-like filtrate of the blood

Question 4

Filtration at the glomeruli is what?

Answer 4

Not particularly selective

Question 5

What is filtration at the glomeruli influenced slightly by?

Answer 5

Charge and size of molecules

Question 6

What is the average rate of filtration?

Answer 6

125mL/min or 180L/day

Question 7

Filtration produces how much urine?

Answer 7

1.5L per day

Question 8

The glomerulus has afferent and efferent arterioles supplying it with what?

Answer 8

Blood for filtration

Question 9

What % of cardiac output does the renal blood supply receive?

Answer 9

20-25%

Question 10

At what rate does the renal blood supply receive blood?

Answer 10

1-1.2L/min

Question 11

What is the high flow of renal blood supply for?

Answer 11

Filtration rather than metabolism

Question 12

Where does filtration take place?

Answer 12

In the glomerulus

Question 13

What is the filtration membrane of the glomerulus composed of?
(3)

Answer 13

• Fenestrated endothelium
• Basement membrane
• Podocytes with foot processes and filtration slits

Question 14

Small substances with low molecular mass are what?

Answer 14

Freely filtered

Question 15

Large substances with high molecular mass are what?

Answer 15

Not filtered

Question 16

What is glomerular filtration determined by?

3

Answer 16

• Forces/pressure gradients between glomerular capillary/capsular space
• Permeability of glomerular capillary
• Surface area of glomerular capillary

Question 17

What are the 4 forces determining net filtration pressure?

Answer 17

• Glomerular hydrostatic pressure (GHP)
• Blood colloid osmotic pressure (BCOP)
• Capsular hydrostatic pressure(CsHP)
• Capsular colloid osmotic pressure (CsCOP)

Question 18

What does the Glomerular hydrostatic pressure (GHP) =?

Answer 18

Blood pressure

Question 19

What does the Blood colloid osmotic pressure (BCOP) =?

Answer 19

Albumin

Question 20

What does the Capsular hydrostatic pressure(CsHP) =?

Answer 20

Corpuscle embedded in tissue

Question 21

What does the Capsular colloid osmotic pressure (CsCOP) =?

Answer 21

No protein in the capsular space

Question 22

What force cause filtration into the glomerular space from the capillary?

Answer 22

Glomerular hydrostatic pressure (GHP)

Question 23

What forces cause filtration into the capillary from the capsular space?

Answer 23

• Blood colloid osmotic pressure (BCOP)

- Capsular hydrostatic pressure(CsHP)

Question 24

What is the equation for the clearance of a substance?

Answer 24

Clearance (C) = U x V / P (in mL/min)

Question 25

What does U =?

Answer 25

Concentration of S in urine (mg/L or mol/L)

Question 26

What does V=?

Answer 26

Volume of urine produced per unit time (mL/min or L/hour)

Question 27

What does P=?

Answer 27

Concentration of S in plasma (mg/L or mol/L)

Question 28

What does the equation for renal clearance describe?

Answer 28

The rate at which substance is cleared by the kidney per unit time

Question 29

The equation for renal clearance describes the clearance via the kidneys for what?

Answer 29

All substances that can be detected in plasma and urine

Question 30

What does GFR stand for?

Answer 30

Glomerular filtration rate

Question 31

What is glomerular filtration rate?

Answer 31

Amount of fluid filtered per unit time

Question 32

What is the GFR normally?

Answer 32

Approximately 180 L/day or 125mL/minute

Question 33

GFR is/does what? | 3

Answer 33

- Tightly regulated - Varies from person to person - Declines slowly from age 30

Question 34

To be used as a measure of GFR a substance must what? | 3

Answer 34

- Not be reabsorbed - Not be secreted into the tubule - Not be metabolised

Question 35

What 2 substance fit the conditions to be used as a measurer of GFR?

Answer 35

- Insuline | - Creatinine

Question 36

What is insulin? | 2

Answer 36

- A polysaccharide not metabolised by the body | - Not found in the body, must be injected

Question 37

What is creatine? | 2

Answer 37

- Waste product produced by muscles | - Already in the body so most commonly used clinically

Question 38

What happens to creatine at the glomerulus?

Answer 38

It is filtered freely but not reabsorbed/secreted/metabolised

Question 39

Plasma creatine is an indicator for what?

Answer 39

Kidney function

Question 40

What happens to plasma creatine levels if both kidneys are working?

Answer 40

It is low

Question 41

What happens to plasma creatine if only one kidney is working?

Answer 41

It is still fairly normal

Question 42

What happens if there is critical kidney function?

Answer 42

Kidneys are not working properly and it is important to consider for drug application

Question 43

How much renal blood is filtered?

Answer 43

Only about 20% | half of the CO is plasma therefore it is only 20% of the 1/2 of CO that is filtered

Question 44

What is the filtration fraction?

Answer 44

GFR/RPF

Question 45

What does RPF mean?

Answer 45

Renal plama flow

Question 46

What is filtered load?

Answer 46

The amount of a particular substance (solute) filtered per minute

Question 47

What does filtered load =?

Answer 47

GFR x solute plasma conc.

Question 48

What is a typical value for GFR?

Answer 48

125mL/min