32 :D

Question 1

What is filtration and what is its selectivity and what does it create?

Answer 1

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

Most substances in plasma are freely- filtered
- Not very selective at the glomerulus
- Creates a plasma-like filtrate of the blood

Question 2

What determines glomerular filtration?

Answer 2

• Filtration barrier
• Renal blood flow
• Driving forces

Question 3

Answer 3

Question 4

What’s filtered and what’s not filtered?

Answer 4

• small substances (low molecular mass) are freely
• large substances (high molecular mass) are NOT filtered

Question 5

Albanian can’t pass through

Answer 5

Yep

Question 6

Glomerular filtration: Renal blood flow
- how much CO do they get?
- why?

Answer 6

Renal blood flow (RBF) ≈ 1/5th or 20% of CO per min
RBF ≈ 11 0 0 -1200mL blood/min

high flow for filtration, rather than metabolism

Question 7

Two types of driving forces

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

• Positive pressures favour filtration
• Negative pressures oppose filtration

Question 8

4 pressures / driving forces

Answer 8

Glomerular hydrostatic pressure (GHP)
= blood pressure (+ 50 mmHg)

Blood colloid osmotic pressure (BCOP)
= albumin (- 25 mmHg)

Capsular hydrostatic pressure (CsHP)
= pressure of filtrate already present (- 15 mmHg)

Capsular colloid osmotic pressure (CsCOP)
= no protein in capsular space (+ 0 mmHg)
(If u have a kidney disorder there many be proteins try a pull more fluid from blood)

Question 9

Together the 4 pressures determine the:

Answer 9

Net filtration pressure

(+50) + (-25) + (-15) + (0) = 10 mmHg

Question 10

How much of the kidneys plasma (blood) flow is filtered?

Answer 10

Filtration Fraction

Question 11

Renal Blood Flow, Renal Plasma Flow and Filtration Fraction

Answer 11

Question 12

Filtration Fraction =

Answer 12

Glomerular filtration rate (GFR)
———————————————
Renal plasma flow (RPF)

Question 13

Filtration Fraction calculation =

Answer 13

GFR = 125 mL/min
RPF = 625 mL/min

Filtration Fraction =
125 mL/min
—————— = 1/5th or 20%
625 mL/min

≈ 20% of the RPF is filtered
≈ 80% remains in the glomerular capillaries -> the efferent arteriole -> peritubular capillaries

Question 14

How much plasma is filtered per minute?

Answer 14

Glomerular Filtration Rate (GFR)

Question 15

Glomerular filtration rate - KNOW THESE NUMBERS

Answer 15

Normally:
- 180 L/day
- 125 mL/minute

But produces only 1.5L of urine perday (we reabsortion 99%)
- Tightly regulated
- Variation from person to person
- Declines slowly from age 30

Question 16

How much of a substance is filtered per minute?

Answer 16

Renal Filtered Load

Question 17

What is the renal filtered load?

Answer 17

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

Question 18

How to calculate the filtered load

Answer 18

GFR x solute plasma conc.

Question 19

How to calculate the filtered load - glucose example

Answer 19

e.g. glucose

GFR (125 ml/min) = 0.125 L/min
Plasma glucose conc = 5 mmol/L

Renal filtered load
= 0.125 L/min x 5 mmol/L
= 0.625 mmol/min

Question 20

How much plasma is cleared of a substance per minute?

Answer 20

Renal Clearance

Question 21

What is renal clearance - LEARN

Answer 21

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

Question 22

Renal Clearance can be used to:

Answer 22

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

Question 23

Renal clearncae - creatin and insulin example - how do u calculate it

Answer 23

• 99% of the plasma which was filtered was reabsorbed
• clearance of creatine = volume of plasma filtered per minute = GFR

Question 24

Renal clearance - PAH - how to calculate it?

Answer 24

• clearance of PAH = volume of plasma flowing through the kidneys per minute = RPF

Question 25

Renal clearance - glucose - how to calculate it?

Answer 25

Clearance of glucose - NO plasma is cleared of glucose

Question 26

Renal clearance - sodium - how do you calculate it?

Answer 26

- clearance of sodium = very small volume of plasma per minute

Question 27

Actual calculation for clearance - dont memorise ist understand

Answer 27

The equation describes the clearance (via the kidneys) for all substances that can be detected in plasma and urine!

Question 28

Estimating GFR using Renal Clearance - requirements

Answer 28

To be used to measure GFR a substance must: - Be freely filtered - NOT be reabsorbed from the tubule - NOT be secreted into the tubule

Question 29

Estimating GFR using Renal Clearance - two main substances that meet the requirements

Answer 29

Inulin (not to be confused with insulin!!) • Polysaccharide, not metabolised by body • Not found in body, must be injected Creatinine • Waste product produced by muscles • Already in the body, so most commonly used clinically

Question 30

Food with high inulin

Answer 30

Question 31

Estimating GFR using Renal Clearance - creatine example

Answer 31

Question 32

Relationship between GFR and plasma creatinine

Answer 32

Plasma creatinine conc is an important mark to apply drugs!! indicator of kidney function: - If both kidneys are working (GFR = 125 mL/min) plasma creatinine is low - Even if only one kidney is still working (GFR = 60 mL/min), plasma creatinine is fairly normal - When GFR < 25 mL/min plasma creatinine conc increases as the kidneys ability to clear waste products from the blood is reduced

Question 33

Answer 33

Question 34

GFR, RPF and Renal Clearance

Answer 34

Question 35

GFR ?

Answer 35

The amount of plasma filtered per unit time by the kidneys