Lecture 31 - Glomerular function

Question 1

Filtration:

Answer 1

Movement of plasma from the glomerular capillaries (blood) into the glomerular capsule (nephron)

Question 2

Most substances in plasma are freely-filtered meaning?

Answer 2

Not very selective at the glomerulus

Creates a plasma-like filtrate of the blood

Question 3

What determines glomerular filtration?

Answer 3

Filtration barrier

Renal blood flow

Driving forces

Question 4

Where does filtration occur?

Answer 4

Filtered into capsular space:

small substances (low molecular mass) are freely filtered

large substances (high molecular mass) are NOT filtered

Question 5

What is renal blood flow equal to in the kidneys?

Answer 5

1/5th of CO per min

1100-1200mL blood/min

Question 6

Why is high blood flow in the kidneys needed?

Answer 6

High flow for filtration, rather than metabolism

Question 7

What are the two types of pressures?

Answer 7

Hydrostatic pressures

Pressure due to the volume of fluid
“Pushes” fluid away

Colloid osmotic pressures

Osmotic pressure due to protein
“Pulls” fluid towards

Question 8

What are the 4 forces in the glomerulus?

Answer 8

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

Question 9

What is Glomerular hydrostatic pressure (GHP) equal to?

Answer 9

+ 50 mmHg

Question 10

What is Blood colloid osmotic pressure (BCOP) equal to?

Answer 10

• 25 mmHg

Question 11

What is Capsular hydrostatic pressure (CsHP) equal to?

Answer 11

• 15 mmHg

Question 12

What is Capsular colloid osmotic pressure (CsCOP) equal to?

Answer 12

0 mmHg, If damaged kidneys, there will be a pressure here

Question 13

Proportion/percentage of the kidneys plasma flow is filtered is called?

Answer 13

Filtration fraction

Question 14

Renal plasma flow :

Answer 14

45% of blood is cells

55% of blood is plasma

Question 15

Filtration factor:

Answer 15

1/5th of the plasma which enters the kidneys (renal plasma flow) is filtered through the glomeruli into the nephrons

Question 16

≈ 20% of the RPF is filtered in the?

Answer 16

glomerular capsule

nephron

Question 17

≈ 80% remains in the glomerular capillaries

Answer 17

the efferent arteriole

peritubular capillaries

Question 18

GFR – Glomerular filtration rate

Answer 18

The amount of plasma filtered per unit time by the kidneys

Question 19

Renal plasma flow (RPF) x Filtration fraction (FF) =

Answer 19

Glomerular filtration rate (GFR)

Question 20

GFR = ? (mL/min)

Answer 20

125 mL/min

Question 21

RPF = ? (mL/min)

Answer 21

625 mL/min

Question 22

Glomerular filtration rate is?

Answer 22

Tightly regulated

Varies from person to person

Declines slowly from age 30

Question 23

Renal Filtered Load (RFL)

Answer 23

How much of a substance in the plasma is filtered per minute?

Question 24

Filtered Load =

Answer 24

the amount of a particular substance (solute) in the plasma is filtered per unit of time (per minute/hour/day)

= GFR x solute plasma conc.

Question 25

Renal Clearance

Answer 25

How much plasma is cleared of a substance per minute

Question 26

Clearance?

Answer 26

is the volume (mL) of plasma that is cleared of a substance by the kidneys per unit time (per minute)

Question 27

Clearance can be used to:

Answer 27

Quantify how a substance is handled by the kidneys Estimate glomerular filtration rate (GFR)

Question 28

Creatinine and inulin are?

Answer 28

Freely filtered Not secreted Not reabsorbed ALL filtered is excreted in urine

Question 29

Clearance of creatinine =

Answer 29

= Volume of plasma filtered per minute = GFR

Question 30

How much of creatinine is filtered?

Answer 30

20% of plasma filtered Creatinine will be excreted in urine

Question 31

Medications and toxins (e.g. PAH) are?

Answer 31

Freely filtered Entirely secreted Not reabsorbed ALL in blood is excreted in urine

Question 32

Clearance of PAH =

Answer 32

Volume of plasma flowing through the kidneys per minute = RPF

Question 33

How much of PAH is filtered?

Answer 33

20% of plasma filtered ALL PAH which is filtered stays in the nephrons PAH is entirely secreted so ALL PAH in the blood of the peritubular capillaries is secreted into the nephrons This PAH will be excreted in the urine

Question 34

Glucose is?

Answer 34

Freely filtered Not secreted Fully reabsorbed in the proximal tubule NONE excreted in urine Except diabetes

Question 35

Clearance of Glucose =

Answer 35

NO plasma is cleared of glucose = 0

Question 36

How much of glucose is filtered?

Answer 36

NO glucose will be excreted in the urine NO plasma has been “cleared” of glucose

Question 37

Sodium is?

Answer 37

Freely filtered Not secreted Almost fully reabsorbed in most parts of the nephron Small amount excreted in urine

Question 38

Clearance of sodium =

Answer 38

Very small volume of plasma per minute

Question 39

How much of sodium is filtered?

Answer 39

A small amount of sodium is not reabsorbed This sodium will be excreted in the urine Almost all of the sodium which is filtered is reabsorbed A small amount of the plasma which was filtered has been reabsorbed without sodium and has been “cleared” of sodium

Question 40

Clearance can be used to:

Answer 40

Quantify how a substance is handled by the kidneys Estimate glomerular filtration rate (GFR) Estimate renal plasma flow (RPF)

Question 41

To be used to measure GFR a substance must:

Answer 41

Be freely filtered NOT be reabsorbed from the tubule NOT be secreted into the tubule

Question 42

What two main substances meet the requirements to measure GFR?

Answer 42

Inulin and creatinine