Filtration

Question 1

What do the kidneys filter?

Answer 1

Blood

Question 2

What is the main function of the kidneys?

Answer 2

To maintain homeostasis of the body

Question 3

Where does filtration occur within the kidneys?

Answer 3

Glomerular capillaries

Question 4

What is the purpose of filtration?

Answer 4

To form an essentially protein-free filtrate of plasma

Question 5

How much is the Glomerular Filtration Rate (GFR)?

Answer 5

180L/day

Question 6

What % of the cardiac output do the kidneys receive?

Answer 6

20-25%

Question 7

How long does it take for total blood volume to pass through the kidneys?

Answer 7

Approx. five minutes

Question 8

Important to note that none of the RBC’s or WBC’s and only a fraction of the plasma are filtered into the Bowman’s capsule.
Where does the rest of the plasma pass?

Answer 8

Passes via efferent arterioles into peritubular capillaries and then into the renal vein

Question 9

What is glomerular filtration dependant on the balance of?

Answer 9

The balance between hydrostatic forces favouring filtration and oncotic pressure forces favouring reabsorption

Question 10

RECAP- what % of total blood volume does plasma make up?

Answer 10

55%

Question 11

The glomerular barrier is selectively permeable. What factors determine if a substance can cross?

Answer 11

Molecular size
Electrical charge
Shape

Question 12

List some substances which are freely filtered by the glomerular barrier.

Answer 12

Sodium, potassium. chlorine, water, urea, glucose, sucrose, polyethylene-glycol

Question 13

Give some examples of substances which cannot pass through the glomerular barrier.

Answer 13

Haemoglobin
Serum albumin

Question 14

There are three layers of filtration in the glomerular membrane.
What are the three layers?

Answer 14

1. Fenestration of endothelial cells
2. Basal lamina of glomerulus
3. Slit membrane between pedicels

Question 15

What is the function of the fenestration of endothelial cells as a filter layer?

Answer 15

Prevents filtration of blood cells but allows all components of blood plasma to flow in

Question 16

What is the function of the basal lamina as a filter layer?

Answer 16

Prevents filtration of larger proteins

Question 17

What is the function of the slit membrane as a filter layer?

Answer 17

Prevents filtration of medium size proteins

Question 18

Describe the structure of afferent arterioles.

Answer 18

Short and wide

Question 19

Describe the structure of efferent arterioles.

Answer 19

Long and narrow

-> think a before e in alphabet so longer way through alphabet, longer structure

Question 20

Why is glomerular capillary pressure higher than most of the other capillaries in the body?

Answer 20

Arrives in afferent arterioles which are short and wide and blood arriving at the glomerulus still has a high hydrostatic pressure

Question 21

Regarding the golden rule of circulation, what happens to hydrostatic pressure if there is high resistance?

Answer 21

Upstream- increased pressure
Downstream- decreased pressure

Question 22

Does hydrostatic pressure favour filtration or reabsorption?

Answer 22

Filtration

Question 23

Does oncotic pressure favour filtration or reabsorption?

Answer 23

Reabsorption

Question 24

What happens to oncotic and hydrostatic pressure as blood passes through the glomerulus?

Answer 24

Oncotic pressure increases but never exceeds high hydrostatic pressure

->as hydrostatic pressure favours filtration

Question 25

What is the only process which occurs at the glomerular capillaries?

Answer 25

Filtration

Question 26

What is the net filtration pressure?

Answer 26

10 mm Hg -> this is because hydrostatic pressure is usually around the range of 55mmHg and then oncotic pressure (30mmHg) and fluid pressure (15mmHg) counteract so.... 50-30-15=10 idk if that makes sense sorry gal

Question 27

In normal physiology, what affects glomerular filtration rate?

Answer 27

Afferent and efferent arteriolar diameter and the balance of resistance between them

Question 28

However, GFR can be affected by extrinsic factors like what?

Answer 28

1. Sympathetic nerves 2. Circulating catecholamines 3. Angiotensin II

Question 29

Which are more sensitive to sympathetic nerves causing constriction; afferent or efferent arterioles?

Answer 29

Afferent

Question 30

Give some examples of catecholamines and what their function is.

Answer 30

Adrenaline, noradrenaline Act as vasoconstrictors

Question 31

What role does angiotensin II have on GFR?

Answer 31

Vasoconstrictor which works at low concs. on efferents and high concs. on both efferent and afferent

Question 32

Renal vasculature also exhibits a well-developed intrinsic ability to adjust resistance in response to changes in arterial blood pressure. This essentially keeps blood flow and GFR constant. What is this known as?

Answer 32

Autoregulation

Question 33

Okayy imma reverse the question- what is autoregulation regarding filtration?

Answer 33

Renal vasculature has intrinsic ability to adjust resistance in response to changes in arterial blood pressure. This essentially keeps blood flow and GFR constant.

Question 34

In humans, when BP is between 60-130, what happens to rate of glomerular filtration?

Answer 34

No changes as normal BP

Question 35

In humans, when BP is below 60, what happens to rate of glomerular filtration?

Answer 35

Filtration would decrease ->if under 50, filtration stops

Question 36

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

Answer 36

Automatic increase in afferent arteriolar constriction, preventing a rise of glomerular capillary pressure ->another form of autoregulation

Question 37

Does autoregulation depend on anything?

Answer 37

No, independent of nerves or hormones ->occurs in denervated and isolated perfused kidneys

Question 38

In situations where blood volume or pressure face serious compromise, e.g. haemorrhage, what happens?

Answer 38

Activation of sympathetic nerves and autoregulation can be overridden ->this means blood goes to more important organs

Question 39

However, while reduction in renal blood flow can supply organs with as much as 800ml /min, what happens if renal blood flow is reduced for a prolonged period of time?

Answer 39

Irreparable damage which can lead to death

Question 40

100% of plasma volume enters the glomerular capillaries via which type of arteriole?

Answer 40

Afferent arteriole

Question 41

20% of the plasma volume is filtered out, what happens to the rest?

Answer 41

Enters efferent arteriole and passes onto peritubular capillaries

Question 42

Out of 20% of plasma which is filtered out, how much is reabsorbed?

Answer 42

19%

Question 43

What happens to the 1% of plasma which is fiiltered?

Answer 43

Excreted

Question 44

Which type of capillary is responsible for reabsorption?

Answer 44

Peritubular capillaries