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TUBULAR
REABSORPTION
DR.NILESH KATE.
M.D.
ASSOCIATE PROFESSOR,
DEPARTMENT OF
PHYSIOLOGY,
 The composition of the blood ( internal
environment ) is determined not by what
the mouth ingest but by what the kidney
...
OBJECTIVES
 General principles of renal tubular transport.
 Transport across different segments of renal tubule.
 Renal...
TUBULAR FUNCTION
 Reabsorption: Removal of a
substance from the filtrate
Filtered load
--excretion.
 180 lit filtered – ...
GENERAL PRINCIPLES.
 Renal tubular Transport.
 Transport across cell membrane.
 Transepithelial transport.
 Parameters...
Renal tubular Transport.
 Across cell membrane.
 Passive transport.
 Diffusion.
 Facilitated
diffusion.
 Active trans...
TRANSEPITHELIAL TRANSPORT.
 Transcellular
 Apical membrane
 Basolateral
membrane.
 Paracellular.
Tubular mechanism.
 Tubular reabsorption
 Active transport – Solutes.
 Passive movements -- water.
PATTERN OF RENAL HANDLING
 Glomerular filtration only
 Glomerular filtration & partial reabsorption.
 Glomerular filtra...
PATTERN OF RENAL HANDLING
 Glomerular filtration & tubular secretion.
 Glomerular filtration & partial reabsorption &
se...
Transport across different
segments of renal tubule.
 Across proximal
tubule.– absorbs
 67% of filtered water,
Na, Cl, K...
Proximal tubule reabsorption.
 Characteristics of PCT
 VILLI
 Key element
 Na- K-ATPase in Basolateral membrane.
Sodium reabsorption.
 Early Proximal
tubule.
 ISOOSMOTIC.
 Basolateral
membrane
 Apical membrane
 Na-H antiporter.
 ...
LATE PROXIMAL TUBULE.
WATER REABSORPTION.
 2/3rd
Transcellular
 1/3rd
Paracellular.
TRANSPORT ACROSS LOOP OF
HENLE
 Thin descending limb
of loop of Henle.
 Thin Ascending limb
of loop of Henle.
 Thick as...
Transport across distal tubule & collecting
duct.
 Early distal tubule
 Na-Cl symporter
 Cortical diluting segment.
 T...
TRANSPORT ACROSS DISTAL TUBULE
& COLLECTING DUCT.
 Principal cells
 Na reabsorption.
 Cl reabsorption.
 ADH – AQUAPRIN...
RENAL HANDLING OF SODIUM
& WATER.
 Site & mechanism of
reabsorption of Na.
 Proximal tubule – 67% (active)
 LH – 20%
 ...
Water reabsorption.
11
Proximal convoluted tubule.
(PASSIVE)
Loop of Henle
(IMPERMEABLE)
Distal convoluted tubule.
(IMPERM...
Water reabsorption.
 Obligatory. (85%)
 Transtubular osmotic
gradient
 67% (PCT)
 15-18% (DTS)
 Facultative.
 From c...
MECHANISM OF ACTION OF
DIURETICS.
Bicarbonate Reabsorption
BICARBONATE REABSORPTION IN
PCT
Bicarbonate Reabsorption
 95%
 The epithelial cells of the
proximal tubule, the thick
segment of the ascending
loop of H...
Bicarbonate Reabsorption
 5%
 Primary Active
Secretion of
Hydrogen Ions
 Intercalated Cells of
Late Distal and
Collecti...
RENAL HANDLING OF GLUCOSE.
 Glomerular filtration
 Tubular reabsorption
 Carrier mediated Na-glu
cotransport.
 Facilit...
Glucose titration curve.
 Filtered load
 Renal threshold. (180
mg%)
 Transport maximum.
(350 mg %)
 Splay.
 Causes.
...
APPLIED
 Mechanism of actions of Diuretics.
 Renal handling of clearance.
 Importance of ADH.
 Basis of counter curren...
Thank
You
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TUBULAR REABSORPTION

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TUBULAR REABSORPTION

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TUBULAR REABSORPTION

  1. 1. TUBULAR REABSORPTION DR.NILESH KATE. M.D. ASSOCIATE PROFESSOR, DEPARTMENT OF PHYSIOLOGY,
  2. 2.  The composition of the blood ( internal environment ) is determined not by what the mouth ingest but by what the kidney keep. ------- SMITH.
  3. 3. OBJECTIVES  General principles of renal tubular transport.  Transport across different segments of renal tubule.  Renal handling of common solutes & water.  Renal threshold,  Tubular maximum.
  4. 4. TUBULAR FUNCTION  Reabsorption: Removal of a substance from the filtrate Filtered load --excretion.  180 lit filtered – 178.5 lit reabsorbed only 1.5 lit excreted.  Determine composition & volume of urine.  Consequently control volume, osmolality, composition & pH of ICF & ECF.
  5. 5. GENERAL PRINCIPLES.  Renal tubular Transport.  Transport across cell membrane.  Transepithelial transport.  Parameters of active transport.  Transport across different segments.  Proximal tubule.  Henle’s loop.  Distal tubule  Collecting duct.  Tubular transport of common solute & water.  Tubular transport of Na, Cl, K, Glucose & water.
  6. 6. Renal tubular Transport.  Across cell membrane.  Passive transport.  Diffusion.  Facilitated diffusion.  Active transport.  Carrier mediated.  Endocytosis.
  7. 7. TRANSEPITHELIAL TRANSPORT.  Transcellular  Apical membrane  Basolateral membrane.  Paracellular.
  8. 8. Tubular mechanism.  Tubular reabsorption  Active transport – Solutes.  Passive movements -- water.
  9. 9. PATTERN OF RENAL HANDLING  Glomerular filtration only  Glomerular filtration & partial reabsorption.  Glomerular filtration & complete tubular reabsorption.
  10. 10. PATTERN OF RENAL HANDLING  Glomerular filtration & tubular secretion.  Glomerular filtration & partial reabsorption & secretion.  No Glomerular filtration , no absorption
  11. 11. Transport across different segments of renal tubule.  Across proximal tubule.– absorbs  67% of filtered water, Na, Cl, K  All glucose & amino acids.  Do not reabsorbs  Inulin, creatinine, sucrose, mannitol
  12. 12. Proximal tubule reabsorption.  Characteristics of PCT  VILLI  Key element  Na- K-ATPase in Basolateral membrane.
  13. 13. Sodium reabsorption.  Early Proximal tubule.  ISOOSMOTIC.  Basolateral membrane  Apical membrane  Na-H antiporter.  Na-Glu symporter.
  14. 14. LATE PROXIMAL TUBULE.
  15. 15. WATER REABSORPTION.  2/3rd Transcellular  1/3rd Paracellular.
  16. 16. TRANSPORT ACROSS LOOP OF HENLE  Thin descending limb of loop of Henle.  Thin Ascending limb of loop of Henle.  Thick ascending limb of loop of Henle. ( Loop diuretics)
  17. 17. Transport across distal tubule & collecting duct.  Early distal tubule  Na-Cl symporter  Cortical diluting segment.  Thiazide diuretics.  Late distal tubule & collecting duct.  Principal cells  Intercalated cells.
  18. 18. TRANSPORT ACROSS DISTAL TUBULE & COLLECTING DUCT.  Principal cells  Na reabsorption.  Cl reabsorption.  ADH – AQUAPRINS  Water channels.  Role of aldosterone on Principal cells.  Increases Na reabsorption.  Intercalated cells  Reabsorb K+ & secrete H+
  19. 19. RENAL HANDLING OF SODIUM & WATER.  Site & mechanism of reabsorption of Na.  Proximal tubule – 67% (active)  LH – 20%  DTS – PASSIVE  ATS – PASSIVE  TAL – ACTIVE.  Distal tubule – 7% -- ACTIVE  Collecting duct. – 5% -- ACTIVE  Sodium recycling
  20. 20. Water reabsorption. 11 Proximal convoluted tubule. (PASSIVE) Loop of Henle (IMPERMEABLE) Distal convoluted tubule. (IMPERMEABLE) Collecting duct. REABSORBED (ADH) Glomerular capsule.
  21. 21. Water reabsorption.  Obligatory. (85%)  Transtubular osmotic gradient  67% (PCT)  15-18% (DTS)  Facultative.  From collecting tubule.  Under control of ADH.
  22. 22. MECHANISM OF ACTION OF DIURETICS.
  23. 23. Bicarbonate Reabsorption
  24. 24. BICARBONATE REABSORPTION IN PCT
  25. 25. Bicarbonate Reabsorption  95%  The epithelial cells of the proximal tubule, the thick segment of the ascending loop of Henle, and the early distal tubule  All secrete H+ into the tubular fluid by sodium- hydrogen counter-transport
  26. 26. Bicarbonate Reabsorption  5%  Primary Active Secretion of Hydrogen Ions  Intercalated Cells of Late Distal and Collecting Tubules
  27. 27. RENAL HANDLING OF GLUCOSE.  Glomerular filtration  Tubular reabsorption  Carrier mediated Na-glu cotransport.  Facilitated diffusion.
  28. 28. Glucose titration curve.  Filtered load  Renal threshold. (180 mg%)  Transport maximum. (350 mg %)  Splay.  Causes.  Heterogeneity  Variability in TmG of the Nephron.
  29. 29. APPLIED  Mechanism of actions of Diuretics.  Renal handling of clearance.  Importance of ADH.  Basis of counter current mechanism.  Glycosuria in Diabetes mellitus.  Acidification of urine.
  30. 30. Thank You

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