Lecture 32

Question 1

Filtration by the nephron?

Answer 1

Ultrafiltration

Creates a plasma-like filtrate of the blood.

Question 2

Renal blod flow to and from the glomerulus?

Answer 2

Afferent and efferent arterioles supply the glomerulus with blood for filtration.

Question 3

What is the filtration membrane composed of?

Answer 3

Fenestrated endothelium, basement membrane, and podocytes with foot processes and filtration slots.

Question 4

How does the size of substances affect filtration?

Answer 4

Small substances with low molecular weight will be able to pass through the membrane (freely filtered)

Question 5

What are the driving forces of glomerular filtration determined by?

Answer 5

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

Question 6

What are the four forces (pressures) determining net filtration pressure ?

Answer 6

GHP
BCOP
CsHP
CsCOP

Question 7

What is GHP?

Answer 7

glomerular hydrostatic pressure = Blood pressure (+50mmHg)

Question 8

What is BCOP?

Answer 8

blood colloid osmotic pressure = albumin (-25mmHg)

Question 9

What is CsHP?

Answer 9

capsular hydrostatic pressure = corpuscle embedded in tuissue (-15mmHg)

Question 10

What is CsCOP)?

Answer 10

capsular colloid osmotic pressure = no protein in capsular space (+ 0 mmHg)

Question 11

Equation for clearance?

Answer 11

(Cs) = Us x V / Ps (in mL/min)

Question 12

What is Us?

Answer 12

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

Question 13

What is V?

Answer 13

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

Question 14

What is Ps?

Answer 14

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

Question 15

What is the purpose of this equation?

Answer 15

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

Question 16

What is the Glomerular Filtration Rate?

Answer 16

GFR is the amount of fluid filtered per unit time. • normally ~180 L/day or 125 mL/minute

Question 17

What factors determine whether a substance can be used as a measure of GFR?

Answer 17

• not be reabsorbed from the tubule
• not be secreted into the tubule
• not be metabolised

Question 18

What two substances are often used as a measure of GFR?

Answer 18

Inulin and creatinine

Question 19

What is Inulin?

Answer 19

• polysaccharide not metabolised by body

* not found in body, must be injected

Question 20

What is Creatine?

Answer 20

• waste product produced by muscles

* already in the body so most commonly used clinically

Question 21

Why is measuring the renal clearance of Creatine ideal for clinically estimating GFR?

Answer 21

creatinine is filtered freely at the glomerulus but is not reabsorbed, secreted or metabolised!!!!

Question 22

What is the relationship between GFR and Creatinine?

Answer 22

plasma creatinine is an indicator for kidney function; plasma creatinine is low, if both kidneys are working (125 mL/min)

Question 23

What is filtration factor?

Answer 23

GFR/RPF

Question 24

What is the filtered load?

Answer 24

Amount of a particular substance solute filtered per minute

GFR x solute plasma conc