1. THREE BASIC RENAL
PROCESSES
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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6. Tubular Reabsorption
By passive diffusion
By primary active transport: Sodium
By secondary active transport: Sugars
and Amino Acids
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7. Tubular Reabsorption is a Function of the
Epithelial Cells Making up the Tubule
Lumen
Cells
Plasma
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9. Rennin-Angiotensin-
Aldosterone System
Stimulates Sodium Reabsorption in distal
and collecting tubules
Naturetic peptide inhibits
In absence of Aldosterone, 20mg of
sodium/day may be excreted
Aldosterone can cause 99.5% retention
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11. DIURETICS
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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12. Glucose and Amino Acids are reabsorbed by
secondary active transport
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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13. GLUCOSE REABSORPTION HAS A
TUBULAR MAXIMUM
Glucose Filtered Excreted
Reabsorbed
mg/min
Reabsorbed
Renal threshold (300mg/100 ml)
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Concentration
16. DUAL CONTROL OF
ALDOSTERONE SECRETION
Fall in sodium
Increased
Plasma ECF Volume
Potassium
Blood Pressure
Increased Aldosterone secretion
Increased Tubular Increased Tubular
Potassium Secretion Sodium Reabsorption
Increased Urinary
Fall in Urinary
Potassium Secretion
Sodium Excretion
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17. Reabsorption in Proximal
Tubule (Summary)
Glucose and Amino Acids
67% of Filtered Sodium
Other Electrolytes
65% of Filtered Water
50% of Filtered Urea
All Filtered Potassium
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18. Secretion in Proximal
Tubule (Summary)
Variable Proton secretion for acid/base
regulation
Organic Ion secretion
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19. Reabsorption in Distal
Tubule (Summary)
Variable Sodium controlled by
Aldosterone
Chloride follows passively
Variable water controlled by vasopressin
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20. Secretion in Distal Tubule
(Summary)
Variable Proton for acid/base regulation
Variable Potassium controlled by
aldosterone
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21. Collecting Duct (Summary)
Variable water reabsorption controlled by
vasopressin
Variable Proton secretion for acid/base
balance
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23. Medullary countercurrent
system
Osmotic gradient established by long
loops of Henle
Descending limb
Ascending limb
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24. Descending limb
Highly permeable to water
No active sodium transport
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25. Ascending limb
Actively pumps sodium out of tubule to
surrounding interstitial fluid
Impermeable to water
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26. COUNTERCURRENT MAKES
THE OSMOTIC GRADIENT
From To Distal
Cortex
Proximal 300 300 100 Tubule
Tubule 450 250 Medulla
450
600 600 400
Active 750 550
750
Sodium
Transport 900 900 700
1050 1050 850
Passive 1200 1200 1000
Water
Transport 1200 1200 1000
Long Loop
of Henle
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27. THE OSMOTIC GRADIENT CONCENTRATES
THE URINE WHEN VASOPRESSIN (ANTI
DIURETIC HORMONE [ADH]) IS PRESENT
Interstitial Fluid From
Distal Cortex
300 300
Tubule
400 Medulla
450
Collecting
550
600 Duct
750 700
900 850
1050 1000
Pores 1100
1200
Open
1200 1200
Passive Water Flow
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28. WHEN VASOPRESSIN (ANTI DIURETIC
HORMONE [ADH]) IS ABSENT A DILUTE
URINE IS PRODUCE
Interstitial Fluid From
Distal Cortex
300 100
Tubule
100 Medulla
450
Collecting
100
600 Duct
750 100
900 100
1050 100
Pores 100
1200
Closed
1200 100
No Water Flow
Out of Duct
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29. Renal Failure
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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30. THE URINARY BLADDER
STORES THE URINE
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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31. Reflex and Voluntary
Control of Micturition
Bladder filling Stretch receptors in
reflexively contracts bladder send
the bladder inhibitory impulses to
Internal Sphincter external sphincter
mechanically opens Voluntary signals
from cortex can
override the reflex or
allow it to take place
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