Mammalian Kidney

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Mammalian Kidney

• Comparative Animal Physiology

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Today
I. Structure of the nephron II. Mechanism of
urine concentation III. Specialization of nephron
membranes IV. Summary of nephron function V.
Animal of the Day
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Exchanges between fluid compartments allow
regulation of all body fluids
Where enter?
largest
E.C.F.
20 of cardiac output
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Urine Production
I. Glomerular ultrafiltration- keeps lg. proteins
cells 125 ml/min into Bowmans capsule (20
of plasma flow). II. Tubular reabsorption 99 of
water most of salts reabsorbed. III. Tubular
secretion Active transport into urine increases
H etc..
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Ultrafiltration
4 factors determine rate
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3
4
hiP
2
hiR
fenestrated
2
Millions in human
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Nephron morphology
Distal tubule
Proximal tubule
Ascending limb
Descending limb
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osM
(1) NaCl active out (2) H2O follows (3) Urea
concentrates and leaks out at end. (4) H2O
follows from descending, concentrating lumen (5)
NaCl follows from ascending
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Structure
Process
75 of NaCl H2O regained by Na/K ATPase
passive Cl Glucose A.A.s also reabsorbed
Absorb proteins by pinocytosis.
Glomerulus
(capillary)
Filtration
Proximal
Reabsorption
convoluted
Secret H if necessary.
tubule
Secretion
Reabsorption
Loop of
Henle
Reabsorption
Distal
convoluted
Secretion
tubule
Collecting
Reabsorption
duct
Hypertonic urine
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Structure
Process
Glomerulus
(capillary)
Filtration
Proximal
Reabsorption
Permeable to H2O not NaCl urea H2O passive
osmosis concentrate
convoluted
tubule
Secretion
descending
Reabsorption
Loop of
Henle
Permeable to NaCl not H2O urea NaCl leaks out
ascending
Reabsorption
Distal
convoluted
Secretion
tubule
Collecting
Reabsorption
duct
Hypertonic urine
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Structure
Process
Glomerulus
(capillary)
Filtration
Proximal
Reabsorption
convoluted
tubule
Secretion
Reabsorption
Loop of
Henle
Medullary limb
ascending
Reabsorption
Distal
convoluted
Active xport NaCl not H2O
Secretion
tubule
Collecting
Reabsorption
duct
Hypertonic urine
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Structure
Process
Glomerulus
(capillary)
Filtration
Proximal
Reabsorption
convoluted
tubule
Secretion
Reabsorption
Loop of
Henle
Reabsorption
Active xport Na
Distal
convoluted
Secretion
tubule
Active secrete K, H, NH3
Aldosterone increases both
Collecting
Reabsorption
duct
Hypertonic urine
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Structure
Process
Glomerulus
(capillary)
Filtration
Proximal
Reabsorption
convoluted
tubule
Secretion
Reabsorption
Loop of
Henle
Reabsorption
Distal
convoluted
Secretion
tubule
H2O diffuses out to high osM
ADH increases perm. H2O
Collecting
Reabsorption
duct
Hypertonic urine
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Homeostasis of filtration
Sympathetic NS
Myogenic response
Constrict due to high flow in tubule
Renin
LowNaCl
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Blood volume regulation
Low-Pressure, 1.Renin//Angiotensin/ (constrict
efferent) Aldosterone/ (resorb Na) 2.ADH/vasopress
in (resorb H2O) by increasing permeability
High-volume, Atrial naturietic peptide, inhibits
renin reduces Na resorption
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Summary of nephron function
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Change in solutes down tubule
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Some mammals can drink seawater
When a whale and a human ingest 1 liter of sea
water Sea water consumed Urine produced Net
effect Volume Cl- Volume Cl- on water
balance (ml) (mM) (ml) (mM)
(ml) Human 1000 535 1350 400
-350 Whale 1000 535 650 820 350
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THE ANIMAL OF THE DAY (PhChordata, GeDipodomys)