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94 Cards in this Set
- Front
- Back
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functions of kidney
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filter blood plasma
regulate blood volume and pressure regulate osmolarity regulate PCO2 acid-base balance synthesize calcitrol gluconeogenesis |
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enzymes kidney secretes
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renin
erythropoietin |
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renin
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enzyme that activates hormonal response to control BP
secreted from JG cells in nephron loop when drop in BP |
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erythropoietin
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stimulates production of red blood cells
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gluconeogenesis
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amino acids to energy in extreme starvation; occurs in kidneys
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urea
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by-product of protein catabolism
protein --> AA and then NH2 group removed most toxic of wastes, but liver quickly converts ammonia to urea |
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uric acid
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catabolism by-product of nucleic acids
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creatine
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catabolism of creatine phosphate
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BUN
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blood nitrogenous waste level
10-20 mg/dL |
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elevated BUN
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azotemia = renal insufficiency and can progress to uremia (diarrhea/vomiting)
caused by low rates of filtration |
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respiratory system excretes
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CO2
small amts other gases and water |
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integumentary system excretes....
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water
inorganic salts lactic acid urea |
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digestive system eliminates.... and excretes....
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food residue;
water salts CO2 lipids bile |
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urinary system excretes....
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metabolic wastes
toxins/drugs hormones salts H+ water |
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glomerular filtration
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water and some solutes in blood plasma pass from capillaries of glomerulus into capsular space of nephron
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filtration membrane layers
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fenestrated endothelium
basement membrane filtration slits of podocytes |
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fenestrated endothelium
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highly permeable, but exclude blood cells from filtrate
70-90 nm |
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basement membrane
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proteogylcan gel that excludes > 8 nm
blood protein level 7% and filtrate protein level .03% |
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filtration slits of podocytes
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arms with pedicles that wrap around capillaries
negatively charged filtration slits between them additional obstacle to large anions |
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what can pass through the filtration membrane?
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water
electrolytes glucose fatty acids amino acids wastes vitamins |
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proteinuria/hematuria
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kidney deficiency that allows proteins/blood to pass through the urine
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BHP
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blood hydrostatic pressure
much higher than elsewhere 60 mmHg |
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hydrostatic pressure in capular space
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~18 mmHg
due to high filtration rate and continual accumulation of fluid |
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COP
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colloid osmotic pressure
blood about the same as everywhere else in the body 32 mmHg |
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Net filtration pressure
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high outward of 60
opposed by two inward of 18 and 32 net = 10 mmHg out |
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nephrosclerosis
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scarring of the kidney from rupture
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atherosclerosis
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renal blood vessels from rupture
positive feedback loop --> renal failure |
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GFR
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glomerular filtration rate
amt of filtrate formed per minute between two kidneys for every 1 mmHg net filtration pressure, kidneys produce 12.5 mL filtrate (10 times 12.5 = 125 mL/min) |
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filtration coefficient Kf
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depend on permeability and surface area
10% lower in women (10.5 mL) |
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daily filtration
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about 60X blood volume per day
99% reabsorbed --> 1-2L of urine/day |
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if GFR is too high...
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fluid flows too rapidly for them to reabsorb usual amount so urine output rises
dehydration electrolyte depletion |
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if GFR is too low....
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fluid sluggish and reabsorb waste --> azotemia
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3 ways to change GFR =
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renal autroregulation
sympathetic control hormonal control |
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renal autoregulation
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ability of nephrons to adjust their own blood flow independent of systemic blood pressure
myogenic mechanism tubuloglomerular feedback |
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myogenic mechanism
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tendency of smooth muscles to contract when stretched
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increasing arterial BP in myogenic mechanism
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stretch afferent arteriole which constricts and prevents blood flow into glomerulus
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decreasing arterial BP in myogenic mechanism
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afferent arteriole relaxes and allows blood to flow more easily into glomerulus
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mechanism of vasoconstriction
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pressure induced vascular wall stretch --> depolarization --> Ca 2+ influx
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tubuloglomerular feedback
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function adjusted based on downstream feedback from juxtaglomerular apparatus
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juxtaglomerular apparatus
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end of nephron loop where it comes into contact with afferent and efferent arterioles from the glomerulus
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macula densa
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patch of close epithelia cells facing arterioles to sense variations in flow
secrete paracrine that stimulates JG cells |
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JG cells
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enlarged smooth muscle cells in afferent arteriole directly across from macula dense that dilate/constrict
secrete renin in response to drop in BP |
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mesangial cells
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clef between afferent and efferent arterioles
also to build supportive matrix for glomerulus constrict/relax to regulate capillary flow communicate via paracrines |
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When GFR rises with tubuloglomerular response...
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flow of tubular fluid increase and more NaCl reabsorbed
macula densa stimulates JG with paracrine which constrict afferent mesangial may contract too |
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when GFR falls with tubulogomerular response...
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macula relaxes afferent and mesangial cells --> blood flow increase
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MAP range GFR remains stable
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90-180 mmHg
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sympathetic control
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in strenuous exercise and acute conditions
adrenal epinephrine constricts afferent arterioles --> reduced GFR and urine output and redirects blood from kidneys to heart/brain/muscles |
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hormonal control drop in BP....
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sympathetic fibers stimulate JG cells to secrete renin
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what does renin do in hormonal control
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converts angiotensinogen (blood protein) --> angiotensin I
lungs and kidneys convert angiotensin I --> II which is active via ACE |
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effects angiotensin II at glomerulus and peritubular capillaries
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widespread vasoconstriction throughout the body
constricts more efferent than afferent, raising GFR lowers BP in peritubular capillaries which enhances reabsorption of NaCl and water from nephron |
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effects angiotensin II at DCT and CD
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stimulates adrenal cortex to release aldosterone which targets DCT and CD to reabsorb Na and water
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angiotensin II effects at collecting tubule
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stimulates posterior pituitary to secrete ADH which promotes water reabsorption by CD
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angiotensin II effects at hypothalamus
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stimulates thirst and H2O intake
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angiotensin II effects overall
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increase reabsorption rate of Na and H2O
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why can filtration occur in glomerulus
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high BP of glomerular capillaries override colloid osmotic pressure
most plasma solutes into capsular space while retaining formed elements and protein in bloodstream |
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tubular reabsorption
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reclaiming water and solutes from tubular fluid and returning them to blood
conversion of glomerular filtrate to urine |
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where does tubular reabsorption occur?
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from PCT to DCT
most return through walls of peritubular capillaries and vasa recta |
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what gets reabsorbed in tubular?
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water
glucose AA Na+ K+ Ca++ Cl- |
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PCT reabsorption
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about 65% glomerular filtrate reabsorbed
microvilli and SA lots of mitochondria for active transport |
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PCT transcellular route
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through cytoplasm and out base of epithelia cells
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PCT paracellular route
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between cells where junctions are leaky and allow water to drag substances through
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PCT Na reabsorption
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creates osmotic/electrical gradient that drives others
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symports
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simulatenously bind Na and glucose/AA/lactate
no ATP, but driven by Na/K pumps at base of the cell which pump Na out of the cell into capillaries |
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antiport
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pulls Na into cell while pumping H out into tubular fluid
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Cl reabsorption
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Cl follows Na into tubular cells
also antiports in exchange for other ions |
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Cl and K reabsorption
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driven out through basal by symport
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K/Mg/P reabsorption
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through paracellular route
P also co-transported with Na |
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Glucose reabsorption
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co-transported with Na and ejected by facilitated diffusion
finite # carrier molecules so removal depends on BGL |
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urea reabsorption
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through tubular epithelium with water
about half of urea |
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water reabsorption
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about 2/3 of all
tissue fluid is hypertonic because of all the salts/organic solutes while osmolarity of tubular fluid remains the same because equal amts of water and solutes are reabsorbed in PCT |
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uptake into capillaries in PCT
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H2O reabsorbed by capillaries via osmosis and solvent drag
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factors that promote osmotic movement into peritubular capillaries
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high interstitial fluid pressure
less resistance to absorption proteins remain in blood |
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high interstitial fluid pressure
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from accumulation of reabsorbed fluid around basolateral that drives water into capillaries
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less resistance to reabsorption
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narrow efferent arterioles lower BHP in capillaries so less resistance to more entering fluids
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proteins remain in blood after filtration
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elevating COP
high COP and low BHP in capillaries and high hydrostatic pressure in tissue fluid --> reabsorption |
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accentuation of reabsorbing properties by angiotensin II
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constricts arterioles, reducing BP in PTC, reducing resistance to reabsorption
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tubular secretion in PCT waste removal of:
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urea
uric acid bile acids ammonia catecholamines prostaglandins some creatine drugs |
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tubular secretion in acid-base balance
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secretion of H and H2CO3 ions
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nephron loop
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generates osmotic gradient that enables CD to concentrate urine and conserve water
reabsorb useful electrolytes from filtrate ~ 25% of Na, K and Cl |
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cells in thick segment of ascending nephron loop
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simulatenously bind 1 Na, 1 K and 2 Cl
Na transported out of epithelial to medullary tissue fluid while K/Cl diffuse out K --> through epithelial Na/K pump and then back to tubular fluid H2O can't follow --> diluted urine |
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DST and CD reabsorb
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variable amounts of water and salts regulated by hormones
still contains 20% of water and 7% of salts from glomerule filtrate |
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principle cells of DST and CD
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more abundant
receptors for hormones involved in solute and H2O balance |
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intercalated cells of DST and CD
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reabsorb K and secrete H into tubule for acid-base balance
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water conservation of CD
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begins in cortex which receives multiple nephron inputs
as it passes through medulla, it reabsorbs water and concentrates urine 4X |
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four hormones involved in reabsorption in DCT/ CD
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ADH, aldosterone, parathyroid hormone, natriuretic peptides
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medulla for water conservation
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as you go deeper, it gets saltier
CD not permeable to NaCl, but it is permeable to water so more water leaves as CD gets deeper into medulla concentrates urine |
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drinking lots of water on CD...
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water diuresis so cortical CD reabsorbs NaCl, but is impermeable to water
this means that there is less of an osmolarity gradient when passes through salty medulla so it reabsorbs less water and urine becomes dilute |
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dehydration on CD....
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high blood osmolarity --> ADH released which increases water reabsorption
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aquaporins
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increase in number at surface stimulated by ADH
if lasts more than a day, will transcribe more |
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extreme dehydration
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BP so low that GFR significantly reduce --> increased water reabsorption, decreased urine volume
filtrate is slow so more time |
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countercurrent multiplier
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ability to concentrate urine depends on osmotic gradient of renal medulla
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how does nephron loop recapture salt and return it to deep medullary tissue
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since descending is only permeable to water and ascending is only permeable to salt, this keeps the salinity of the medulla
tubular fluid is really concentrated at bottom and then dilute at top |
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vasa recta
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network of vessels that arise from nephrons deep in cortex close to medulla
from efferent arterioles carry away water and solutes reabsorbed by tubule |
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countercurrent system with vasa recta
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descending capillaries exchange H2O for salt and ascending do the opposite
net effect --> vasa recta gives salt back and doesn't subtract from osmolarity of medulla |
