Exam 4: Glomerular Filtration 157 - 166

Question 1

4 main functions of the kidney:

Answer 1

1. Regulation of concentration fo ions
2. Excretion of organic compounds
3. Fluid balance
4. Acid-base balance

And

5. BP reg
6. RBC vol reg
7. Vit D activation

Question 2

Nephron refers to which microanatomy of the kidney?

Answer 2

• Glomerular capsule (GC)
• proximal convoluted tubule (PCT)
• loop of Henle
• distal convoluted tubule (DCT)
• collecting duct

Question 3

Vasculature of the microanatomy of the kidney:

Answer 3

• Intralobular artery
• afferent arterioles
• glomerulus
• efferent arterioles
• peritubular capillaries (vasa rectae)
• venule
• intralobular vein

Question 4

Kidneys/nephrons engage in 3 broad-scope activities

Answer 4

Filtration
Reabsorption
Secretion

Question 5

Clearance

Answer 5

The amount of plasma cleared of a given substance

Question 6

What drives filtration and absorption process?

Answer 6

BP

• HIGH BP in glomerular capillaries
• LOW BP in peritubular capillaries

Question 7

Renal blood flow to the kidneys is how much (renal fraction)

Answer 7

~1,000-1,200 ml/min to kidneys

Note: overall strategy of urinary system is to filter HUGE amounts of blood and recover nearly all the good stuff from it.

Question 8

Kidneys get what percent of cardiac output?

Answer 8

20-25%

Question 9

What is the renal fraction?

Answer 9

The renal blood flow:

• 1,000-1,200 ml blood/min
• 20-25% cardiac output (but really 10-30%)

Question 10

Glomerular filtrate

Answer 10

Amount of plasma “lost,” aka captured by Bowman’s capsule, from the blood volume

Question 11

Glomerular filtration rate per day

Answer 11

160-180 l/day (2x a person’s body weight)

Question 12

Glomerular filtration recovery length

Answer 12

1-2 l/day as urine

Question 13

What are the 3 layers of the glomerulus and glomerular membrane?

Answer 13

[ blood ] 
- type II capillaries
- basement membrane
- podocyte
[ capsular space ]

Question 14

What is special about type II capillaries?

Answer 14

Allows for substantial filtering because its a hundred times more permeable than type I capillaries

Question 15

What is important about the basement membrane of the glomerulus/glomerular membrane?

Answer 15

Blocks proteins because it has negatively charged BM materials that repel positively charged plasma proteins

Question 16

What is good about podocytes?

Answer 16

The slit-pores (between pedicels) allows what remains (from type II capillary and basement membrane) to flow into glomerular space

Question 17

Capillary (blood) pressure is how much?

Answer 17

60 mmHg

So this is a outward force/pushing fluid out

Question 18

Colloidal (plasma) osmotic pressure is how much

Answer 18

32 mmHG (varies 28-36 mmHg)

This is an inward force

Question 19

Capsular (Bowman’s) pressure of filtrate is how much?

Answer 19

18 mmHg

So this is an inward, backward force

Question 20

Where is the sum directional flow of blood, plasma and Bowman’s pressure going?

Answer 20

Into the kidney

Net driving force (NDF): 60 + (-)32 + (-)18 = 10 mmHg

Question 21

What is the equation for the glomerular filtration rate (GFR)?

Answer 21

Kf X NDF

Kf = Filtration coefficient 
NDF = net driving force

Question 22

What is the number for filtration coefficient (Kf)?

Answer 22

Kf = 12.5 ml/min/mmHg

Question 23

What is the net driving force (NDF) number?

Answer 23

NDF = 10 mmHg

Question 24

What is the glomerular filtration rate (GFR)?

Answer 24

125 ml/min

GFR = Kf X NDF
= 12.5 X 10
= membrane permeability X force

Question 25

What is glomerular filtration rate (GFR) per day?

Answer 25

180 liters per day

Question 26

GFR is affected by

Answer 26

• glomerular pressure
• plasma colloidal osmotic pressure
• Bowman’s capsular pressure
• glomerular capillary permeability
• glomerular capillary total surface area