Kidney Tubular Function Flashcards
what does sodium transport facilitate?
reabsorption of nutrients, water and ions
how much is reabsorbed in the PCT?
65%
how much is absorbed in the ascending loop of Henle?
25%
how much is reabsorbed in the DCT?
up to 8%
how much sodium is reabsorbed?
98%
what does ADH do in the DCT?
targets the epithelium in the DCT and tells it to insert aquaporins
what is the overall function of ADH inserting aquaporins in the DCT?
to maintain homeostasis of the internal fluid compartment
what signals the release of the hormones in the DCT?
changes in blood pressure (decreased for ADH and aldosterone and increase for ANP)
if ADH inserts aquaporins the what does aldosterone insert in the DCT?
sodium channels
collectively what do ADH and aldosterone action result in in the DCT?
fluid reabsorption producing a small volume of concentrated urine which increases homeostatic regulation of blood pressure and volume
what is the action of ANP in the DCT?
fluid excretion which leads to large volume of dilute urine and then decreased homeostatic regulation of blood volume and pressure
what hormones does a decrease in blood pressure release?
ADH and aldosterone
what hormones does an increase in blood pressure release?
ANP
what is glomeruluar filtration rate?
the rate at which blood is filtered through the glomerulus into the Bowman’s capsule
what is GFR influenced by?
glomerular hydrostatic pressure, capsular hydrostatic pressure, glomerular osmotic pressure, systemic blood pressure, renin-angiotensin-aldosterone system and disease
if the GFR is greater what does it mean for sodium?
there is less time to reabsorb it in the glomerulus so there is a higher concentration of it in the DCT
what is reabsorbed in the PCT?
65% Na and water, 100% glucose and amino acids, 50% waste (urea)
what is reabsorbed in descending loop of Henle?
water
what is reabsorbed in the ascending loop of Henle?
25% Na (+ K and Cl)
what is reabsorbed in the DCT?
<8% Na and water
what does the juxta-glomerular apparatus do?
connects the DCT with the glomerulus and measures and responds to changes in Na+ concentration of the filtrate
what is reabsorbed in the collecting tubules?
water
what does excretion equal?
(filtration - reabsorption) + secretion
what does the macula densa do?
detects concentration of sodium in the filtrate
what do the juxtaglomerular cells do?
adjust the diameter of the afferent arteriole when it receives signals from the macula densa
what are the modified smooth muscle cells?
mesangial cells and supporting cells
what needs to happen for juxtaglomerular cells to be effected?
the macula densa must release adenosine
what is the sequence of events if glomerular hydrostatic pressure is increased?
increased BP - increased glomerular hydrostatic pressure - increased GFR - increased sodium filtrate conc. - macula densa released adenosine - juxtaglomerular cells swell which constricts afferent arteriole and decreased hydrostatic pressure
what does tubuloglomerular feedback regulate?
systemic blood pressure
what happens when the macula densa shrivels?
they release prostaglandins
why would the macula densa shrivel?
decreased sodium concentration in filtrate
what happens when the macula densa swells?
release adenosine
what makes the macula densa swell?
increased sodium filtrate concentration
what is the sequence of events if the glomerular hydrostatic BP is decreased?
decreased BP - decreased glomerular hydrostatic pressure - decreased GFR - decreased sodium conc. in filtrate - macula densa release prostaglandins - juxtaglomerular cells maintain the afferent arteriole diameter but secretes renin to activate renin-angiotensin system
how does the renin-angiotensinogen restore blood pressure?
via angiotensin 2
describe the process in which renin-angiotensinogen restores blood pressure
1 - angiotensinogen released into circulation, 2 - renin converts angiotensinogen into angiotensin 1, 3 - angiotensinogen converting enzyme converts angiotensin 1 into 2, 4 - angiotensin 2 is a potent vasoconstrictor and rapidly increases blood pressure
where is angiotensin released from?
the liver
where does angiotensin 2 bind to target receptors on and for what?
arterioles for constriction, hypothalamus for thirst, pituitary gland for release of ADH, adrenal medulla for release of aldosterone
how does angiotensin 2 restore blood volume?
via increased fluid and salt retention
where is the ANP released from?
from epithelial cells in the lining of the atrium of the heart which have baroreceptors to know when to release the peptide
summarise what happens when there is high concentration of sodium and it is detected by the juxtaglomerular apparatus?
release aldosterone - vasoconstriction - tubuloglomerular feedback
what does tubuloglomerular feedback ensure?
that the capillaries do not get damaged
summarise what happens when there is a low concentration of sodium and it is detected by the juxtaglomerular apparatus?
release of prostaglandins - renin release - activation of RAAS
summarise the actions of ANP
it counteracts ADH and renin to remoe excess fluid and lower blood pressure
what happens to GFR as kidney disease worsens?
it decreases
how does kidney disease affect the CVS?
GFR is decreased which activates RAAS system which increases BP
what are the consequences of chronic kidney disease?
inadequate removal of fluid and waste products of metabolism, inappropriate activation of RAAS
what are the causes of chronic kidney disease?
hypertension, diabetes, high cholesterol, kidney infections, glomerulonephritis, polycystic kidney disease, kidney stones, long-term use of NSAIDs
what two causes of kidney disease can be related to oral bacteria
kidney infections and glomerulonephritis
when do kidney stones develop?
when waste starts to crystallise which blocks kidney function
what are the symptoms of chronic kidney disease?
hypertension, nausea, oedema in hands., ankles feet or lungs, blood/protein in urine, anaemia and weak/painful bones
how is hypertension regulated?
diet/weight loss, combination of anti-hypertensive treatments, diuretics, ACE inhibitors/angiotensin receptor blockers, aldosterone agonists
how do ACE inhibitors/angiotensin receptor blockers work?
prevent conversion of angiotensin 1 to angiotensin 2
what is kidney failure?
stage 5 kidney disease, end stage renal disease with less than 15% kidney function, dialysis and/or kidney transplant required
what is dialysis
artificial removal of waste, solutes, water and toxins from blood
what are the 2 types of dialysis?
haemodialysis, peritoneal dialysis
