Glomerular Filtration And Regulation Of Renal Blood Flow

Question 1

What structures is the renal corpuscle made up of?

Answer 1

Glomerulus and bowmans capsule

Question 2

Why is the epithelium of the bowmans capsule invaginated?

Answer 2

To coat the podocytes on the capillaries

Question 3

What are the key features of the glomerular filtrate?

Answer 3

• small solutes have the same concentration in glomerular filtrate and plasma
• almost no proteins

Question 4

What is proteinuria a sign of?

Answer 4

Renal/ urinary tract disease

Question 5

What drives the ultrafiltration process?

Answer 5

Net pressure drop across the glomerular membrane due to plasma proteins

Question 6

What drives glomerular fluid formation?

Answer 6

Imbalance of starlings forces

Question 7

What are the forces acting on the bowman’s capsule?

Answer 7

Capillary blood pressure (out)
Plasma colloid osmotic pressure (in)
Pressure in bowmans space (in)

Question 8

What is the formula for net filtration force in the bowmans capsule?

Answer 8

Net filtration force = capillary blood pressure - (plasma colloid osmotic pressure + Pu)

Question 9

What is the plasma colloid osmotic pressure?

Answer 9

Pressure created by things that can’t pass through the membrane

Question 10

What happens to the pressures in the blood vessel as you move from the afferent to the efferent ends?

Answer 10

Capillary blood pressure drops and plasma colloid osmotic pressure increases

Question 11

What is absorption driven by?

Answer 11

A decrease in blood pressure to the point that its less than the plasma colloid osmotic pressure and stuff is pulled back into capillary

Question 12

What are the gaps between the pedicels called?

Answer 12

Filtration slits

Question 13

What’s a pedicel?

Answer 13

podocyte foot processes

Question 14

How big are filtration slits?

Answer 14

30nm

Question 15

What is the structure of a filtration slit?

Answer 15

Central spine with lateral rings

Question 16

What do the subdivides split the filtration slit into?

Answer 16

Pores 4nm wide

Question 17

What are filtration slits made of?

Answer 17

Proteins (nephrin and podocin)

Question 18

What does deficiency of nephrin or podocin cause?

Answer 18

Nephrotic syndrome

Question 19

How does the Bayliss myogenic response happen?

Answer 19

Increase in perfusion pressure -> Brief increase in vessel radius -> blood flow goes up -> stretch in smooth muscle lead to contraction and flow returns to control value

Question 20

What is oliguria?

Answer 20

Little urine

Question 21

What causes oliguria?

Answer 21

Failure of auto regulation in hypotension

Question 22

Where type of cells are juxtaglomerular cells?

Answer 22

Modified smooth muscle cells

Question 23

Where are the juxtaglomerular cells found?

Answer 23

Walls of afferent arterioles proximal to the glomerulus

Question 24

What are the stages in tubuloglomerular feedback?

Answer 24

GFR increases -> flow through tubule and macula densa increases -> paracrine diffuses from macula densa to afferent arteriole -> afferent arteriole constricts

Question 25

Why does the flow rate past the macula densa increase?

Answer 25

Alter the [NaCl] and luminal osmolality

Question 26

What does NaCl make macula densa cells do?

Answer 26

Release ATP

Question 27

What does ATP release from macula densa cells cause?

Answer 27

Contraction of smooth muscle cells in the afferent arteriole

Question 28

What extrinsic controls are there of GFR?

Answer 28

Renal sympathetic nerves

Question 29

What 3 conditions cause the renal sympathetic nerves to control GFR?

Answer 29

Orthostasis, heavy exercise and haemorrhage and other forms of clinical shock

Question 30

In shock, how are the sympathetic actions in the kidney aided?

Answer 30

Circulating vasoconstrictor hormones such as adrenaline, angiotensin and vasopressin

Question 31

How do sympathetic nerves control GFR?

Answer 31

Reset auto regulation to a lower level

Question 32

What are the two major clinical disorders that affect GFR?

Answer 32

Glomeruli too leaky to plasma protein

GFR too low

Question 33

What can cause the glomeruli to be too leaky to plasma protein?

Answer 33

Nephrotic syndrome

Question 34

What are the three causes of nephrotic syndrome?

Answer 34

Proteinuria, hypoproteinaemia, oedema

Question 35

What type of medication does nephrotic syndrome respond well to?

Answer 35

Steroids

Question 36

What can cause the GFR to be too low?

Answer 36

Chronic glomerulonephritis

Question 37

What does chronic glomerulonephritis look like?

Answer 37

Fibrosed glomeruli- almost no blood flow