Glomerular Filtration and Calculations

Question 1

Is everything able to into Bowmans space?

Answer 1

No, due to 3 barriers of filtration

Question 2

What limits surface area for filtration?

Answer 2

Slits between podocytes

Question 3

What is the % of blood that is filtered into Bowmans space from each glomerulus?

Answer 3

20%

Question 4

How does unfiltered blood exit the capillaries?

Answer 4

Leaves through the efferent arterial

Question 5

What are the 4 pressures that affect glomerular filtration?

Answer 5

1. Hydrostatic Pressure of Glomerular Capillaries
2. Colloid Osmotic pressure of Glomerular Capillaries
3. Hydrostatic Pressure of Bowmans Capsule
4. Colloid Osmotic Pressure of Bowmans Capsule

Question 6

What happens when net filtration pressure is positive?

Answer 6

Plasma will filter into Bowmans space

Question 7

What happens when net filtration pressure is 0 or less?

Answer 7

Plasma will not filter out of the glomerular capillaries

Question 8

What is proper filtration pressure?

Answer 8

10mmHg

Question 9

What is Hydrostatic Pressure of Glomerular Capillaries?

Answer 9

The pressure of the fluid in the glomerulus

• pressure caused by blood flowing into the glomerulus
• promotes filtration
• largest pressure (55mmHg)

Question 10

What is colloid osmotic pressure of glomerular capillaries?

Answer 10

Within the glomerulus there are proteins which are attracted to water.

• The pressure is caused by the presence of proteins in the glomerulus
• inhibits filtration (30mmHg)

Question 11

What is Hydrostatic pressure of Bowmans capsule?

Answer 11

The pressure caused by filtrate that remains in Bowmans space
-inhibits filtration (15mmHg)

Question 12

What is Colloid osmotic pressure of Bowmans Capsule?

Answer 12

Pressure caused by the presence of proteins IF in Bowmans capsule (because proteins shouldn’t be in this space)
-Promotes filtration IF proteins are present in Bowmans Space

Question 13

What is the Globular Filtration Rate (GFR)?

Answer 13

The amount of fluid/solutes that are filtered per unit time into Bowmans space

Question 14

What happens when if renal blood flow or blood pressure increases?

Answer 14

Would result in an increase in net filtration

Question 15

What are the 2 things that affect GFR?

Answer 15

Net Filtration Pressure

Filtration Coefficient

Question 16

What is the filtration coefficient?

Answer 16

Due to the leakiness of the globular capillaries

• really hard to measure
• influenced by the surface area of the capillaries and the permeability between capillaries

Question 17

What happens when GFR increases and decreases?

Answer 17

When GFR increases more solutes are excreted

When GFR decreases less solutes are excreted

Question 18

What is Net Filtration pressure influenced by?

Answer 18

Renal Blood flow

Blood Pressure

Question 19

What is the filtration coefficient influenced by?

Answer 19

The surface area of the capillaries available for filtration

The permeability of barriers between capillaries and Bowmans Capsule

Question 20

How do wed regulate GFR?

Answer 20

Auto-regulatory mechanisms are triggered to maintain blood pressure within the glomerulus of each nephron even when body blood pressure is high

Question 21

What are the 2 auto-regulatory mechanisms used to regulate GFR?

Answer 21

Myogenic response

Tubuloglomerular Feedback

Question 22

What is the Myogenic response?

Answer 22

Quickly modifies how much fluid is being filtered

-modifies how fast blood is going through the corpuscle

Question 23

What is tubuloglomerular feedback?

Answer 23

When the actual content of the filtrate can also regulate the GFR locally with help of the macula dense cells

Question 24

What is the function of the macula dense cells?

Answer 24

Act as salt detectors in tubuloglomerular feedback

Question 25

In tubuloglomerular feedback, what happens when blood pressure increases?

Answer 25

Increased blood pressure increases the amount of fluid being filtered. As a consequence of that is the increase in NaCl being filtered. When NaCl is too high, macula dense cells release a paracrine factor that stimulate the afferent arteriole specifically to constrict and therefore reduce GFR

Question 26

How is the GFR mostly regulated?

Answer 26

Via local constriction of the afferent and efferent arterioles

Question 27

What happens to filtration when the afferent arteriole constricts?

Answer 27

A decrease in diameter will decrease blood flowing into the glomerulus. -less blood=less pressure=less fluid can filter

Question 28

What happens when the efferent arteriole constricts?

Answer 28

A decrease in diameter increases the GFR - Blood cant leave as fast, pooling up in the corpuscle - Pressure of blood increases= increases filtration rate

Question 29

What happens when both afferent and efferent arterioles are restricted?

Answer 29

GFR decreases - but the first constriction (afferent) is more important - there is less blood entering through afferent

Question 30

How do you measure GFR?

Answer 30

Through urine analysis

Question 31

What is the excretion equation?

Answer 31

Filtration - Reabsorption + Secretion

Question 32

What is the right substance to test GFR with?

Answer 32

A substance that is filtered easily but not reabsorbed into the body and it fully excreted in the urine

Question 33

What are some examples of the "right" substance to measure GFR in urine?

Answer 33

Waste products | Creatinine

Question 34

Where does creatinine come from?

Answer 34

Creatinine comes from Creatine which is found in bones. The amount of Creatinine will depend on how much bone you have

Question 35

What is renal handling?

Answer 35

What happened to the substance after it got filtered into Bowmans space

Question 36

What is the filtered load equation?

Answer 36

[X]substance in plasma x GFR

Question 37

How can % reabsorption change?

Answer 37

Depending on how much is ingested