the kidney- reabsorption

?
the kidneys maintain fluid and electrolyte balance in accordance with the principle of
'mass balance'
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mass balance=
existing body load + intake or metabolic production - excretion or metabolic removal
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kidneys regulate the amount of urine produced and its components through:
- reabsorption
- excretion
(thirsty= inc reabsorption of water by the kidneys)
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input
intake through intestine, lungs, skin
metabolic production
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output
excretion by kidneys, liver, lungs, skin
metabolism to a new substance
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osmotic equilibrium
osmolarity= conc of combined solutes in water
water crosses membranes freely from low to high solute conc
primary solutes are Na^+ and K^+
implications for cell vol
high solute conc= low water conc and vice versa
not being in osmotic equilibrium can affe
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hypotonic
may lead to bursting of the cell
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hypertonic
may lead to shrinking of the cell
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regulation of fluid balance
this process is finely tuned to maintain homeostasis of blood vol, blood pressure, plasma osmolarity and blood pH
most imp is control of Na^+ (regulates blood vol)
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water will follow the movement of sodium if
that membrane is permeable to water
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sodium regulation relies on a balance between
sodium being filtered and absorbed
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body detects changes in sodium (salt) levels indirectly as changes in blood vol
and therefore detects this with the baroreceptors and osmoreceptors in the hypothalamus
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what also regulates total body sodium?
blood vol
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low sodium=
low blood vol
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high sodium=
high blood vol
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electrolyte balances
have consequences in the body
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how the kidneys fulfill their homeostatic function
regional differences in the permeability of the nephron and collecting duct to water
regional differences in the selective reapsorption and secretion of solutes in the nephron and collecting duct
the arrangement and proximity of the peritubular capillari
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vasa recta
blood vessels surrounding the loop of Henle
thus anything surrounding the loop of Henle can be rapidly absorbed
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tubular transport
two membrane surfaces must be crossed for reabsorption
- basolateral membrane (adjacent to interstitial fluid)
- luminal membrane (adjacent to tubular fluid)
from tubular filtrate into tubular cell along conc gradient
some substances require facilitated d
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transcellular route (through the cell)
- transport across the apical membrane
- diffusion through cytosol
- transport across basolateral membrane
- movement through interstitial fluid and into capillary
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paracellular route (through tight junctions)
- movement through leaky tight junctions
- movement through interstitial fluid and into capillaries
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passive transport
movement of substances within the cells along the conc gradient
does not require energy
can involve transmembrane proteins
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active transport - the Na^+/ K^+ ATPase
the enzymatic equivalent of the Na^+/ K^+ pump
powered by ATP
moves Na^+ and K^+ in opposite directions
recall that active transport (in general) SELECTIVELY moves molecules against a conc gradient
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movement of water
osmosis
facilitated diffusion (via aquaporins (proteins))
regulated in the kidney by hormones
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Loop of Henle
countercurrent multiplier system in Loop of Henle
countercurrent exchange in vasa recta
creates a hypertonic renal medulla
produces concentrated urine
1- filtrate entering the descending limb becomes progressively more concentrated as it loses water
2- bl
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key point about the loop of Henle
in the ascending limb the movement of water by osmosis is NOT coupled to the reabsorption of solutes
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what allows for absorption in the ascending and descending limb?
the differential permeability of the limbs
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counter current multiplier in the loop of Henle
1- more salt is continually added by the PCT
2- the higher the osmolarity of the ECF, the more water leaves the descending limb by osmosis
3- the more water that leaves the descending limb, the saltier the fluid is that remains in the tubule
4- the salti
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counter current exchange in the vasa recta
important component of the counter current multiplier
permeable to salt and water- salt in vasa recta is able to get back into loop of Henle
reabsorbs water in ascending limb
recirculates salt in interstitial fluid to maintain osmolarity
vasa recta is res
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reabsorption in the thick segment of ascending loop
not permeable to water
Na^+ moves by AT, and K^+ and Cl^- move by cotransport out of the ascending limb of the loop of Henle
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reabsorption in the DCT and collecting duct of the loop of Henle
water moves out of the DCT and collecting duct by osmosis
Na^+ moves by AT and Cl^- moves by cotransport out of the DCT and collecting duct
the reabsorbed water and solutes enter the peritubular capillaries and vasa recta
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reabsorption is regulated by
hormones
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water is never absorbed in
the first part of the DCT
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secondary transport
the movement of one molecule allows a second molecule to move against its conc gradient ('uphill')
does not require energy (instead uses the electro-chemical gradient created)
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acid-base balance
reabsorption of Na^+ (secondary transport) and HCO3^- (facilitated diffusion) and secretion of H^+ in the PCT
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reabsorption of glucose in the PCT
Facilitated diffusion and secondary transport
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proximal convoluted tubule
Na^+ - active transport
organic nutrients and certain ions- co transport
water- osmosis
lipid- soluble substances- transcellular route
Cl^-, HCO3^-, K^+ paracellular route
1- solute molecules, such as amino acids, glucose and fructose, as well as Na^+, C
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movement of water and other ions is dependent on
the conc of sodium
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total body mass female
45% solids
55% fluids
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total body mass male
40% solids
60% fluids
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fluids
2/3 ICF
1/3 ECF (80% interstitial fluid + blood vessel)
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Other cards in this set

Card 2

Front

mass balance=

Back

existing body load + intake or metabolic production - excretion or metabolic removal

Card 3

Front

kidneys regulate the amount of urine produced and its components through:

Back

Preview of the front of card 3

Card 4

Front

input

Back

Preview of the front of card 4

Card 5

Front

output

Back

Preview of the front of card 5
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