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Renal Physiology
ch 19
41
Physiology
Undergraduate 3
07/11/2012

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Term
Reabsorption-
Definition
movement of substances from tubules into peritubular capillaries (returned to blood)
Term
Where does most reabsorption occur?
Definition
proximal convoluted tubule, some in distal tubule
Term
What is the barrier for reabsorption?
Definition
epithelial cells of renal tubules and endothelial cells of capillary
Term
solute and water reabsorption depends on-
Definition
transport proteins and membrane permeability to water
Term
Molecules reabsorbed in the proximal convoluted Tubule include:
Definition
glucose, amino acids (both 100% absorbed) sodium, urea, water
Term
Aprox how much filtered water is reabsorbed in PCT? and why?
Definition
65%, due to osmotic gradient produced by the reabsorption of solute.
Term
Glucose and amino acids are co-transported with-- into PCT cells
Definition
sodium
Term
The transporters can be -- meaning that above a certain filrate concentration no further reabsorption occurs and the remainder is--
Definition
saturated, lost in urine
Term
Is there normally glucose in the urine?
Definition
No.
Term
During diabetes mellitus-
Definition
plasma glucose can be as high as 600 mg/100mL which exceeds Tmax (transportation maximum)
Term
Tmax for glucose=
Definition
375 mg/100 mL
Term
Mellitus=
Definition
sweet.
Term
descending loop of henle-
Definition
water reabsorption, 15%, little solute reabsopbed= concentrates the fluid in tubule
Term
ascending loop of henle-
thin portion of loop-
thick-
Definition
sodium and chloride reabsoption.
passive sodium channels
secondary active transporter
Term
Distal Convoluted Tubule (DCT)
Definition
regulates sodium reabsorption
depends on aldosterone secreted by adrenal cortex cells.
Part of RAAS (renal, angiotensin, aldosterone system)
Term
Renin-
Definition
hormone secreated by kidney in response to low plasma sodium or low plasma and ECF volume
Term
aldosterone-
Definition
increases sodium reabsorption from DCT
Term
Collecting duct
Definition
water reabsorption (some sodium)
Term
water reabsorption in DCT depends on
Definition
anti diuretic hormone (ADH, vasopressin)
Term
ADH inserts-
Definition
water channels (aquaporins) into membrane, allows water to move from tubule to cells. Without water can't pass membranes
Term
ADH is produced in , released from
Definition
hypothalamus, posterior pituitary gland
Term
ADH is secreated in response to
Definition
low ECF volume (allows water to be reabsored to increase volume) or increased ECF osmolarity
Term
With no ADH-
Definition
water remains in tubules are is lost in urine
Term
Secretion
Definition
solute moves from peritubular capillaries into tubules
Term
secreated substances:
Definition
potassium, H+ ions, penicillin
Term
To maintain water balance over time:
Definition
intake=output
Term
normovolemia
Definition
normal blood volume
Term
hypervolemia
Definition
high blood volume due to positive water balance
Term
hypovolemia
Definition
low blood volume due to negative water balance
Term
Concentrated v. dilute urine
Definition
A lot of urine- dilute,
small amount- concentrated to conserve water
Term
osmosis
Definition
water moves down concentration gradient,
Term
Proximal tubules reabsorb -
(regulated?)
Definition
70% filtered water and is not regulated
Term
Desending loop of henle reabsorb-
(regulated)
Definition
15% of filtered water, not regulated
Term
Distal tubules and collecting ducts reabsorb-
(regulated?)
Definition
most remaining water, regulated by ADH
Term
what gradient is critical for water reabsorption?
Definition
medullary osmotic gradient
Term
what is the osmotic gradient established by in the loop of henle-
Definition
counter current multiplier
descending is permeable to water but not Na, Cl, or K.
Ascending limb isn't permemable to water but is active transport for Na, Cl, K
Term
filtrate is (more or less) dilute at top of ascending limb?
Definition
More b/c of active transport of Na Cl K
Term
The -- in interstitial fluid favors reabsorption of water from tubules
Definition
large osmotic gradient
Term
In distal tubules and collecting ducts water permeability depends on -
Definition
aquaporin-2 present in apical membrane only when ADH is present
Term
How is the urine with the presence of ADH?
Definition
small vol and concentrated
Term
How is the urine without the presence of ADH?
Definition
no water reabsorption=water is excreted
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