Glomerular Filtration And Regulation Of Renal Blood Flow Flashcards
What structures is the renal corpuscle made up of?
Glomerulus and bowmans capsule
Why is the epithelium of the bowmans capsule invaginated?
To coat the podocytes on the capillaries
What are the key features of the glomerular filtrate?
- small solutes have the same concentration in glomerular filtrate and plasma
- almost no proteins
What is proteinuria a sign of?
Renal/ urinary tract disease
What drives the ultrafiltration process?
Net pressure drop across the glomerular membrane due to plasma proteins
What drives glomerular fluid formation?
Imbalance of starlings forces
What are the forces acting on the bowman’s capsule?
Capillary blood pressure (out)
Plasma colloid osmotic pressure (in)
Pressure in bowmans space (in)
What is the formula for net filtration force in the bowmans capsule?
Net filtration force = capillary blood pressure - (plasma colloid osmotic pressure + Pu)
What is the plasma colloid osmotic pressure?
Pressure created by things that can’t pass through the membrane
What happens to the pressures in the blood vessel as you move from the afferent to the efferent ends?
Capillary blood pressure drops and plasma colloid osmotic pressure increases
What is absorption driven by?
A decrease in blood pressure to the point that its less than the plasma colloid osmotic pressure and stuff is pulled back into capillary
What are the gaps between the pedicels called?
Filtration slits
What’s a pedicel?
podocyte foot processes
How big are filtration slits?
30nm
What is the structure of a filtration slit?
Central spine with lateral rings
What do the subdivides split the filtration slit into?
Pores 4nm wide
What are filtration slits made of?
Proteins (nephrin and podocin)
What does deficiency of nephrin or podocin cause?
Nephrotic syndrome
How does the Bayliss myogenic response happen?
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
What is oliguria?
Little urine
What causes oliguria?
Failure of auto regulation in hypotension
Where type of cells are juxtaglomerular cells?
Modified smooth muscle cells
Where are the juxtaglomerular cells found?
Walls of afferent arterioles proximal to the glomerulus
What are the stages in tubuloglomerular feedback?
GFR increases -> flow through tubule and macula densa increases -> paracrine diffuses from macula densa to afferent arteriole -> afferent arteriole constricts
Why does the flow rate past the macula densa increase?
Alter the [NaCl] and luminal osmolality
What does NaCl make macula densa cells do?
Release ATP
What does ATP release from macula densa cells cause?
Contraction of smooth muscle cells in the afferent arteriole
What extrinsic controls are there of GFR?
Renal sympathetic nerves
What 3 conditions cause the renal sympathetic nerves to control GFR?
Orthostasis, heavy exercise and haemorrhage and other forms of clinical shock
In shock, how are the sympathetic actions in the kidney aided?
Circulating vasoconstrictor hormones such as adrenaline, angiotensin and vasopressin
How do sympathetic nerves control GFR?
Reset auto regulation to a lower level
What are the two major clinical disorders that affect GFR?
Glomeruli too leaky to plasma protein
GFR too low
What can cause the glomeruli to be too leaky to plasma protein?
Nephrotic syndrome
What are the three causes of nephrotic syndrome?
Proteinuria, hypoproteinaemia, oedema
What type of medication does nephrotic syndrome respond well to?
Steroids
What can cause the GFR to be too low?
Chronic glomerulonephritis
What does chronic glomerulonephritis look like?
Fibrosed glomeruli- almost no blood flow
