Kidney Flashcards
roughly how many nephrons do humans have
1 million
which is most outermost; the medulla or the cortex?
cortex
average osmolarity in the PCT
300-400mOsm
average osmolarity at the bottom of the loop of henle
1000-1200mOsm
average osmolarity of the thick ascending loop of henle
100-200mOsm
how many litres of water are filtered a day
180 litres
how many litres of water are excreted a day
1.5 litres
name the three layers in the filtration membrane of the bowmans capsule
endothelial with fenestrations
gel-like basement membrane
slit diaphragms with filtration slits between the podocytes
symptoms of nephrOtic syndrome
high prOtein
Oedema
lOw albumin
hyperlipidemia (increased triglycerides and chOlesterOl)
symptoms of nephrItic syndrome
mild levels of protein in urine
hematuria
hypertension
blurred vision
post streptococcal glomerulonephritis is caused by?
autoimmune reaction 10-14 days after infection caused by streptococcus
immune complexes deposit at glomerular membrane leading to damaged filtration barrier –> loss of protein/albumin in urine
symptoms of post streptococcal glomerulonephritis
hematuria loss of protein in urine decreased blood-albumin oedema (pretty similar to nephrOtic syndrome)
how to diagnose streptococcal glomerulonephritis?
biopsy –> nothing is linear
how to treat strep glomerulonephritis?
no specific treatment - just relieving symptoms
antibiotics used to kill strep
blood pressure meds and diuretics to control swelling and high blood pressure
corticosteroids NOT effective
limit salt diet
what percent of plasma is filtered into the bowman space and PCT
20%
what are diuretics
drugs that increase urine output
what are diuretics used to treat
oedema
congestive heart failure
hypertension
how does mannitol work
increases plasma osmolarity
increases osmotic pressure in glomerular filtrate
decreases h20 reabsorption from nephron
draws fluids from tissues - not brain or eye
what conditions would mannitol be used to treat
forced diuresis - poisonings
glaucoma
cerebral oedema
must be slow filtration to avoid dehydration
what percent of sodium is reabsorbed in the PCT
65-70%
how does sodium leave the nephron tubular lumen into the proximal tubule epithelial cell
co-transport with glucose/amino acids
how does sodium leave the proximal tubule epithelial cell to the blood capillary
3Na+ - 2K+ antiport
sodium out and potassium in
what is SGLT2
sodium/glucose cotransporter
which is more common, SGLT1 or 2
SGLT2 (>90%)
how does SGLT2 work
it pumps both sodium and glucose out of the nephron tubular lumen and into the proximal tubule epithelial cell
how does glucose leave the proximal tubule epithelial cell into the blood capillary
via facilitated diffusion
what do SGLT2 inhibitors treat and how do they work
treat diabetes
by preventing glucose reuptake
what does acetazolamide do? (Carbonic anhydrase diuretic)
suppresses H+ production so reduces Na+ - H+ exchange so less Na+ reabsorption
causes mildly alkaline urine and metabolic acidosis
effect is self limiting
loop of henle TAL - impermeable or permeable to water?
impermeable
what percent of sodium from original filtrate is reabsorbed in the TAL
25%
is the TAL thick or thin?
thick
describe the countercurrent multiplication in the loop of henle
- NaCl actively pumped out of TAL until the ascending limb is 200mOsm
- descending limb is permeable to salt and water so both move back into the loop of henle
- salt and water move up the TAL and salts are pumped out again
- this continues making the salt trapped in the lower medullary interstitum and loop of henle
where do loop diuretics operate
in the ascending limb of the loop of henle
what do loop diuretics target
Na+/2Cl-/K+ co transporter
loop diuretics cause what percent of sodium to be excreted
15-25%
what percent of sodium is reabsorbed in the DCT
5%
how do thiazides work
block Na+/Cl- co transporter resulting in high osmolarity of urine and decreased water reabsorption
effect is self limiting
where do thiazides work
DCT
how are thiazides self limiting
lower blood volume –> renin secretion –> angiotensin formation and aldosterone secretion –> limitation of the effect of thiazides
what percent of sodium is reabsorbed in the collecting duct
1-2%
control of water excretion in the collecting duct is regulated by……?
ADH
what happens to the walls of the distal nephron in the absence of ADH
they are impermeable to water
what is the effect of ADH
increases water permeability of the cortical and medullary collecting ducts
where is ADH produced
hypothalamus
where is ADH stored
posterior pituitary
what receptors does ADH bind to
V2 receptors on the apical cell membranes of the principal cells
what does ADH stimulate the insertion of
aquaporins
what triggers the release of ADH
increase in osmolarity is detected by osmoreceptors which shrink leading to increased frequency of nerve impulses to the posterior pituitary gland leading to the secretion of ADH from nerve terminals
what condition does reduced effectiveness of ADH cause
diabetes insipidus
Symptoms of diabetes insipidus
excretion of large volumes of dilute urine
thirst
what is pituitary (central) diabetes insipidus
head
- no/reduced release of ADH from pituitary gland
- can be successfully treated by self-administered nasal spray providing ADH replacement therapy
what is nephrogenic (peripheral) diabetes insipidus
kidney
- unresponsive to circulatory ADH (lack of V2 receptors in collecting duct)
- genetic - disrupts ability to synthesise aquaporins
what is the mode of action of ENaC blockers
K+ sparing diuretics
directly block epithelial Na+ channel (eNaC) in DCT, collecting tubules and ducts
used in conjunction with loop and thaizide duiretics to maintain K+ balance
what is the mode of action of spironolactone
aldosterone antagonist
action of aldosterone on Na+ reabsorption
early phase: increases opening of ENaC
late phase: promotes DNA transcription, increases synthesis of ENaC and Na+,K+-ATPase
where in the kidney is renin secreted from
juxtaglomerular cells in afferent/efferent arterioles
sympathetic nervous system stimulation increases because of falling blood pressure due to……..
baroreceptors in periphery
intrarenal baroreceptors innervating the juxtamedullary nephron
renin inhibitor inhibits what converting to what
angiotensinogen to angiotensin 1
ACE inhibitor inhibits what converting to what
angiotensin 1 to 2
kidney helps the formation of the active form of which vitamin
vitamin D
what does vitamin D deficiency result in
weak bones in children and adults
what does EPO do in the blood stream
binds with receptors in the bone marrow stimulating red blood cell production
how is EPO synthesised
- reduced oxygen delivery to renal cortex (due to anaemia, altitude, CO poisoning, respiratory disease)
- HIF
- EPO release stimulates bone marrow progenitor cells –> erythrocytes
the kidney accounts for ____% of EPO production in adults
80%
