1.1. Basic Renal Process - Filtration

Question 1

What is the process if the filtration?

Answer 1

The formation of an essentially protein-free filtrate of plasma

Question 2

Where does the process of filtration occur?

Answer 2

At the glomerular capillaries

Question 3

How much of the plasma, from the afferent arterioles, is filtered through the glomerular capillaries?

Answer 3

20%

Question 4

Where is the plasma filtered from / into?

Answer 4

From - The glomerular capillaires

Into - Bowman’s capsule

Question 5

What happens to the remainder of the plasma, which isn’t filtered into the Bowman’s Capsule?

Answer 5

It passed into the efferent arterioles

Question 6

Where does the blood, which passes into the efferent arterioles, travel to?

Answer 6

The peritubular capillaries

Question 7

What are the three layers of the glomerular capillary wall?

Answer 7

1. Endothelial Cells
2. Basal Lamina
3. Podocytes

Question 8

What is special about the Glomerular Endothelial Cells?

Answer 8

It is fenestrated as to prevent blood cells from being filtered, but allowing smaller components of plasma

Question 9

What is special about the Glomerular Basal Lamina?

Answer 9

This prevents larger proteins from being filtered, but allowing smaller components of plasma

Question 10

What is special about the Glomerular Podocytes?

Answer 10

They form a Slit Membrane between Pedicles of the Podocytes, which prevent medium sized proteins from being filtered, but allowing smaller components of plasma

Question 11

How does glomerular filtration occur?

Answer 11

Through the balance of:
1. Hydrostatic Forces
2. Oncotic Pressure
Note - This is the same method as fluid filters through capillaries

Question 12

What force favours filtration?

Answer 12

Hydrostatic forces

Question 13

What force favours reabsorption?

Answer 13

Oncotic pressure (Starling’s Forces)

Question 14

Is the pressure in the Glomerular Capillaries high or low?

Answer 14

High

Question 15

What is responsible for the high glomerular capillary pressure?

Answer 15

1. The afferent arteriole

2. The efferent arteriole

Question 16

1. How are the afferent arterioles described?

2. What is the result of this?

Answer 16

1. Short and Wide
2. This offers little resistance to Flow, allowing for a high hydrostatic pressure to arrive at the glomerular capillaries

Question 17

1. How are the efferent arterioles described?

2. What is the result of this?

Answer 17

1. Long and Narrow

2. This offers high resistance to Flow, allowing for increased pressure upstream (in the Glomerular Capillaries)

Question 18

What happens as a result of the high glomerular capillary pressure?

Answer 18

The hydrostatic forces exceed the oncotic pressure - favouring filtration

Question 19

1. What is the Glomerular Filtration Rate?

2. Is this high or low?

Answer 19

1. 125ml/min

2. High

Question 20

What does the Glomerular Filtration Rate allow the kidneys to do?

Answer 20

Precisely regulate Extra-Cellular Volume

Question 21

What percentage of the renal plasma will become Glomerular Filtrate?

Answer 21

19%

Question 22

What equation which can show the percentage of renal plasma which will become glomerular filtrate?

Answer 22

Plasma = 55% of the total blood volume
Total blood volume = 1200ml/min
Therefore Renal Plasma Flow = 55% of 1200 = 660ml/min
Glomerular Filtration Rate = 125ml/min
Therefore the Filtration Fraction = 125/660 x 100 = 19%

Question 23

What is responsible for regulating the Glomerular Filtration Rate?

Answer 23

1. Afferent Arteriolar Diameter

2. Efferent Arteriolar Diameter

Question 24

What are the extrinsic controls of the Afferent / Efferent Arteriole Diameter?

Answer 24

1. Sympathetic Vaso-Constricting Nerves
2. Circulating Catecholamines
3. Angiotensin II

Question 25

What are the Sympathetic Vaso-Constricting Nerves responsible for?

Answer 25

The constriction of both the afferent and efferent arterioles, but there is a greater sensitivity for the afferent

Question 26

What are the circulating Catecholamines responsible for?

Answer 26

The constriction of primarily the afferent arterioles

Question 27

What is Angiotensin II responsible for?

Answer 27

1. Constriction of the efferent arteriole at low concentrations 2. Constriction of both afferent and efferent arterioles at high concentrations

Question 28

What is a special feature of renal vasculature? And what is it's name?

Answer 28

It exhibits a well-developed intrinsic ability to adjust its resistance in response to changes in arterial blood pressure - Autoregulation

Question 29

What is the function of Autoregulation?

Answer 29

This keeps the blood flow, and therefore the Glomerular Filtration Rate constant over a range of mean blood pressure

Question 30

Over what mean blood pressure can autoregulation keep the Glomerular Filtration Rate constant?

Answer 30

60mmHg - 130mmHg

Question 31

How is autoregulation related to nerves and hormones?

Answer 31

It isn't - it works independently of these and so will occur at the same time

Question 32

What happens below a mean blood pressure of 60mmHg?

Answer 32

Glomerular Filtration Rate falls

Question 33

What happens below a mean blood pressure of 50mmHg?

Answer 33

Glomerular Filtration Rate ceases all together

Question 34

What happens if there is an increase in mean arterial pressure?

Answer 34

There is an automatic increase in afferent arteriolar constriction, preventing a rise in Glomerular Capillary Pressure

Question 35

What happens if there is severe volume compromise (i.e. haemorrhage)?

Answer 35

There is an interaction between intrinsic and extrinsic controls

Question 36

What happens in the interaction between intrinsic and extrinsic controls in situations of severe volume compromise?

Answer 36

1. There is an activation of vaso-constricting nerves and Angiotensin II. This overrides autoregulation

Question 37

What is the purpose of the vaso-constriction and release of Angiotensin II in times of severe volume compromise?

Answer 37

This overrides autoregulation, liberating more blood for more immediately important organs

Question 38

How much blood is freed up by the overriding of autoregulation?

Answer 38

800mls per minute

Question 39

What happens if the blood is diverted away from the kidneys over long periods of time?

Answer 39

Renal damage occurs