renal physiology Flashcards
what is the glomerulus?
epithelial pouch invaginated by capillary tuft
semi-permeable filter
- endothelium
- basement membrane
- epithelium
mesangial cells are specialised smooth muscle cells that support glomerulus _ regulate blood flow and GFR
how is filtration done?
receives 25% of cardiac output (1200ml/min)
20% of blood vol is filtered (250ml/min)
glomerular basement membrane (GBM) is negatively charted so retains anionic (neg) proteins eg albumin which are small enough to pass
filtration is key to excretion of waste, remains constant over range of pressures (80-200mmhg)
glow will depend on Na + water reabsorption
describe Na reabsorption
main factor in determining extracellular volume
low BP and low NaCl at macula densa (that lines DCT distal convoluted tubule)
so renin release
so aldosterone release
more Na/K pumps
describe water reabsorption
determined extracellular fluid osmolality
high osmolality or low BP leads to ADH release
what are the different aspects of the nephron?
PCT- proximal convoluted tubule
thick ascending limb
DCT- distal convoluted tubule
medullary collecting duct
cortical collecting duct
what occurs at proximal convoluted tutuble?
reabsorption of filtrate
70& total Na reabsorption
reabsorption of amino acids, glucose, cations
bicarbonate reabsorbed using carbonic anhydrase
what occurs at thick ascending limb?
creation of osmolality gradient
20% na reasbsorption
Na/K/2Cl triple symporter
what occurs at distal convoluted tubule?
pH + Ca reabsorption
5% Na reabsorption
apical NaCl co-transporter
Ca reabsorption under control of PTH
what occurs at medullary collecting duct?
pH + K regulation
Na reabsorption coupled to K or H excretion
basolateral aldosterone-sensitive Na/K pump
what occurs at cortical collecting duct?
regulation of water reabsorption
controlled by aquaporin-2 channels
what is endocrine function?
secretion of renin by juxtaglomerular apparatus
EPO synthesis
1alpha-hydroxylation of vitamin D controlled by PTH
what are examples of loop diuretics
furosemide
bumetanide
what is the MOA of loop diuretics?
inhibit Na/K/2Cl symporter in thick ascending limb
what is the effect of loop diuretics?
massive NaCl excretion, Ca + K excretion
what is the use of loop diuretics?
rx of oedema in CCF, nephrotic syndrome, hypercalcaemia
what are the SE of loop diuretics?
hypokalaemia
metabolic alkalosis
ototoxic
hypovolaemia
what is an example of thiazide diuretic?
bendroflumethiazide
what is the MOA of thiazide diuretic?
inhibit NaCl co-transporter in distal convoluted tubule
what is the effect of thiazide diuretic?
moderate NaCl excretion
increased Ca reabsorption
what is the use of thiazide diuretics?
HTN
reduce renal stones
mild oedema
what are the SE of thiazide diuretics?
hypokalaemia
hyperglycaemia
increased urate (CI in gout)
what are examples of K sparing diuretics?
spironolactone
amiloride
what is the MOA of K sparing diuretics?
spiro- aldosterone antagonist
amiloride- blocks DCT/CD luminal Na channel
what is the effect of K sparing diuretics?
increased Na excretion
reduced K + H excretion
what is the use of K sparing diuretics?
w loop or thiazide diuretics to control K loss
spiro has long-term benefits in aldosteronism (LF, HF)
what are the SE of K sparing diuretics?
hyperkalaemia
anti-androgenic eg gynaecosmastia
what are examples of osmotic diuretics?
mannitol
what is MOA of osmotic diuretics?
freely filtered + poorly reabsorbed
what is the effect of osmotic diuretics?
reduce brain volume
reduce ICP
what is the use of osmotic diuretics?
glaucoma
raised ICP
rhabdomyolysis
what are the SE of osmotic diuretics?
hyponatraemia
pulmonary oedema
n+v
