HUBS192 Lecture 32 - Renal Physiology: Glomerular Function

Question 1

what is the first part of the basic nephron processes?

Answer 1

filtration

Question 2

what is ultrafiltration?

Answer 2

filtration in a very small area

Question 3

how does the glomeruli select what to filtrate?

Answer 3

selects by size like a sieve

Question 4

what does filtration at the nephron in the kidney create?

Answer 4

creates a plasma-like filtrate of the blood

Question 5

what is the rate of filtration in the nephron in the kidney? (specific number)

Answer 5

takes place at a rate of 125mL/min (180L per day)

Question 6

what 3 things determine renal filtration?

Answer 6

1) renal blood flow (how much blood goes into the kidney to be filtered)
2) filtration barrier (what are the layers of membranes/tissues that make up the filtration barrier)
3) driving forces (physics=pressure)

Question 7

what controls the perfusion of the nephron?

Answer 7

the nephron controls its own perfusion through the distal convoluted tubule

Question 8

how is the glomerulus supplied with blood for filtration?

Answer 8

the glomerulus has afferent and efferent arterioles supplying the glomerulus with blood for filtration

Question 9

what is the percentage of cardiac output for renal blood supply to the kidney?

Answer 9

20-25% of cardiac output (CO)

Question 10

what is the renal blood supply to the kidney per minute? (specific number)

Answer 10

1-1.2L per minute

Question 11

what is the high renal blood flow for in the kidney?

Answer 11

high flow for filtration rather than metabolism

Question 12

where does filtration take place?

Answer 12

filtration takes place in the glomerulus

Question 13

what are the 4 components of the filtration barrier of the kidney?

Answer 13

1) fenestrated endothelium
2) basement membrane
3) podocytes with foot processes
4) filtration slits

Question 14

what is the relationship between small substances and filtration?

Answer 14

small substances (low molecular mass) are free filtered

Question 15

what is the relationship between large substances and filtration?

Answer 15

large substances (high molecular mass) are NOT filtered

Question 16

what are the 3 driving forces of glomerular filtration?

Answer 16

1) forces / pressure gradients between glomerular capillary / capsular space
2) permeability of the glomerular capillary
3) surface area of glomerular capillary

Question 17

what are the 4 forces (pressures) determining net filtration pressure?

Answer 17

1) glomerular hydrostatic pressure (GHP)
2) blood colloid osmotic pressure (BCOP)
3) capsular hydrostatic pressure (CsHP)
4) capsular colloid osmotic pressure (CsCOP)

Question 18

what is the main driving force (pressure) determining the net filtration pressure?

Answer 18

glomerular hydrostatic pressure (GHP)

Question 19

what is the glomerular hydrostatic pressure (GHP)?

Answer 19

blood pressure at + 50 mmHg

Question 20

what is the blood colloid osmotic pressure (BCOP)?

Answer 20

albumin at - 25 mmHg

Question 21

what is the capsular hydrostatic pressure (CsHP)?

Answer 21

corpuscle embedded in tissue at - 15mmHg

Question 22

what is the capsular colloid osmotic pressure (CsCOP)?

Answer 22

no protein in the capsular space at 0mmHg

Question 23

what is the net filtration pressure in terms of mmHg? (specific number)

Answer 23

+ 10mmHg

Question 24

what is the result of filtration of the kidney?

Answer 24

results in an isotonic primary filtrate because it is based on NaCI

Question 25

what is the equation that describes the rate at which substance S is cleared by the kidneys per unit time?

Answer 25

``` Cs = Us x V / Ps (in mL/min) Clearance = concentration of S in urine (mg/L or mol/L) x volume of urine produced per unit time (mL/min or L/hour) / concentration of S in plasma (mg/L or mol/L) ```

Question 26

what is the relationship between the equation for clearance and substances that can be detected in plasma and urine?

Answer 26

the equation describes the clearance via the kidneys for ALL substances that can be detected in plasma and urine

Question 27

what is the letter used to represent clearance of substance?

Answer 27

S

Question 28

what is glomerular filtration rate (GFR)?

Answer 28

amount of fluid filtered per unit time in all of the nephrons present in the body

Question 29

what is the normal glomerular filtration rate (GFR)?

Answer 29

180L per day or 125mL per minute

Question 30

what are the 3 characteristics of the glomerular filtration rate (GFR)?

Answer 30

1) tightly regulated 2) variation from person to person 3) declines slowly from age 30

Question 31

what are the 3 characteristics of the glomerular filtration rate (GFR)?

Answer 31

1) tightly regulated 2) variation from person to person 3) declines slowly from age 30

Question 32

what are the 3 requirements for a substance to be used as a measure of GFR?

Answer 32

1) not be reabsorbed from the tubule 2) not be secreted into the tubule 3) not be metabolised

Question 33

what are the 2 main substances that fit the requirements to be used as a measure of GFR?

Answer 33

1) inulin (NOT INSULIN) | 2) creatinine

Question 34

what is inulin?

Answer 34

a polysaccharide not metabolised by the body | -is not found in the body, must be injected

Question 35

what is creatinine?

Answer 35

a waste product produced by muscles that is already in the body therefore is most commonly used clinically

Question 36

what is renal plasma flow (RPF)?

Answer 36

625 ml of plasma per minute

Question 37

what is the relationship between renal plasma flow (RPF) and glomerulus filtration rate (GFR)?

Answer 37

renal blood flow (RBF) is 625 ml of plasma per minute but only 125 ml of that is filtered per minute from the glomerulus (GFR) -the rest flows through the efferent arteriole

Question 38

what is the filtration fraction?

Answer 38

=(GFR / RPF) | = glomerulus filtration rate / renal plasma flow

Question 39

what is the filtered load?

Answer 39

amount of a particular substance (solute) filtered per minute

Question 40

what is the equation for filtered load?

Answer 40

filtered load = GFR x solute plasma conc.