D. C. Mikulecky Faculty Mentoring Program Virginia Commonwealth Univ. 03/22/22
Dec 30, 2015
Water balanceElectrolyte balancePlasma volumeAcid-base balanceOsmolarity balanceExcretionHormone secretion
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Bowman’sCapsule
Glomerulus
Proximal ConvolutedTubule
Distal ConvolutedTubule
Loop of Henle
Cortex
MedullaArtery
Vein
Peritubular Capillaries
CollectingDuct
Glomerular Filtration: Filtering of blood into tubule forming the primitive urine
Tubular Reabsorption: Absorption of substances needed by body from tubule to blood
Tubular Secretion: Secretion of substances to be eliminated from the body into the tubule from the blood
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GF
TR
TA
Urine Excreted
Efferent ArterioleAfferentArteriole
Glomerulus
KidneyTubule
Peritubular Capillary
First step in urine formation180 liters/day filteredEntire plasma volume filtered 65
times/dayProteins not filtered
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Glomerular CapillaryBlood Pressure + 55
Plasma Colloid Osmotic Pressure
-30
15
10
Bowman’s CapsuleHydrostatic Pressure
-
Net Filtration Pressure +
By passive diffusion
By primary active transport: Sodium
By secondary active transport: Sugars and Amino Acids
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Stimulates Sodium Reabsorption in distal and collecting tubules
Naturetic peptide inhibits In absence of Aldosterone, 20mg of
sodium/day may be excretedAldosterone can cause 99.5%
retention
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Fall in NaCl, extracellular fluid volume, arterial blood pressure
JuxtaglomerularApparatus
ReninLiver
Angiotensin
+
Angiotensin Angiotensin Aldosterone
Lungs
ConvertingEnzyme
AdrenalCortex
IncreasedSodiumReabsorption
HelpsCorrect
ACE Inhibitors (Angiotensin Converting Enzyme): Cause loss of salt---> water follows
Atrial Naturetic Peptide (ANP) also inhibits sodium reabsorption
Osmotic diuretics: Are not reabsorbed
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They are actively transported across the apical cell membranes of the epithelial cells
Their active transport depends on the sodium gradient across this membrane
All other steps are passive
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Renal threshold (300mg/100 ml)
Plasma Concentration of Glucose
GlucoseReabsorbedmg/min
Filtered Excreted
Reabsorbed
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Fall in sodium
ECF Volume
Blood Pressure
Increased PlasmaPotassium
Increased Aldosterone secretion
Increased TubularPotassium Secretion
Increased UrinaryPotassium Secretion
Increased TubularSodium Reabsorption
Fall in Urinary
Sodium Excretion
Glucose and Amino Acids67% of Filtered SodiumOther Electrolytes65% of Filtered Water50% of Filtered UreaAll Filtered Potassium
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Variable Sodium controlled by Aldosterone
Chloride follows passively
Variable water controlled by vasopressin
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Variable water reabsorption controlled by vasopressin
Variable Proton secretion for acid/base balance
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300
450
600
750
900
1050
1200
1200
From ProximalTubule
To DistalTubule
Cortex
Medulla300
450
600
750
900
1050
1200
1200
100
250
400
550
700
850
1000
1000
ActiveSodiumTransport
PassiveWaterTransport
Long Loopof Henle
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From DistalTubule
Cortex
Medulla300
450
600
750
900
1050
1200
1200
300
400
550
700
850
1000
1100
1200
Interstitial Fluid
CollectingDuct
PoresOpen
Passive Water Flow
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From DistalTubule
Cortex
Medulla300
450
600
750
900
1050
1200
1200
100
100
100
100
100
100
100
100
Interstitial Fluid
CollectingDuct
PoresClosed
No Water FlowOut of Duct
Acute: Sudden onset, rapid reduction in urine output - usually reversible
Chronic: Progressive, not reversible
Up to 75% function can be lost before it is noticeable
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Gravity and peristaltic contractions propel the urine along the ureter
Parasympathetic stimulation contracts the bladder and micturition results if the sphincters (internal and external urethral sphincters) relax
The external sphincter is under voluntary control
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