Renal Structure and Function                     1
Kidneys•   Paired•   Retroperitoneal•   Partially protected by the 11th and 12th ribs•   Right slightly lower due to liver...
3
4
Anatomy•   Hilum (hilus)•   Renal artery and vein•   Cortex•   Medulla•   Renal pyramids and renal papillae•   Major and m...
6
• Ureters connect kidneys to urinary bladder• Urethra leads from bladder outside the  body                                 7
8
• Kidneys make up 1 % of body mass, but  receive about 25% of cardiac output.• Kidney has two major functions:  1. Filtrat...
2. Regulation:     Blood volume and composition     Electrolytes     Blood pH     Blood pressure                          ...
Nephron• Functional unit of the kidney• Filtration, tubular reabsorption, tubular  secretion• Renal corpuscle:  – Glomerul...
• Bowman’s capsule  – Receives filtrate• Proximal convoluted tubule  – Reabsorption of water and solutes• Nephron loop or ...
13
14
15
16
Filtration• Renal corpuscle• Filtration membrane  – Fenestrated endothelium of capillaries  – Basement membrane of glomeru...
Forces that influence filtration• Glomerular blood hydrostatic pressure• Opposing forces:  – Plasma colloid osmotic pressu...
19
Glomerular Filtration Rate•   Volume of plasma filtered / unit time•   Approx. 180 L /day•   Urine output is about 1- 2 L ...
21
GFR influenced by:•   Blood pressure and blood flow•   Obstruction to urine outflow•   Loss of protein-free fluid•   Hormo...
Juxtaglomerular apparatus• Juxtaglomerular cells lie in the wall of  afferent arteriole• Macula densa in final portion of ...
24
25
Tubular reabsorption• Water, glucose, amino acids, urea, ions• Sodium diffuses into cell; actively pumped  out – drawing w...
27
28
• In addition to reabsorption, also have  tubular secretion – substances move from  peritubular capillaries into tubules –...
30
• By end of proximal tubule have  reabsorbed:• 60- 70% of water and sodium• about 100% of glucose and amino acids• 90 % of...
Loop of Henle• Responsible for producing a concentrated  urine by forming a concentration gradient  within the medulla of ...
33
Distal convoluted tubule and             collecting ducts•   What happens here depends on ADH•   Aldosterone affects Na+ a...
35
Distal convoluted tubule and           collecting ducts• Tubular secretion to rid body of  substances: K+, H+, urea, ammon...
37
Renal diagnostic procedures• Urinalysis is non-invasive and inexpensive• Normal properties are well known and  easily meas...
pH•   Normally 4.8 – 8.0•   Higher in alkalosis, lower in acidosis•   Diabetes and starvation ↓ pH•   Urinary infections ↑...
Specific gravity• Normal values 1.025 -1.032• High specific gravity can cause  precipitation of solutes and formation of  ...
• Diabetes insipidus = 1.003• Diabetes mellitus = 1. 030• Emesis or fever = 1.040                               41
Microscopic analysis• Red blood cells – should be few or none  – Hematuria – large numbers of rbc’s in urine  – Catheteriz...
• Casts – precipitate from cells lining the  renal tubules  – Red cells – tubule bleeding  – White cells – tubule inflamma...
• Crystals –  – Infection  – Inflammation  – stones                   44
• White blood cells  – Pyuria  – Urinary tract infection• Bacteria                              45
Substances not normally present in             urine•   Acetone•   Bile, bilirubin•   Glucose•   Protein – albumin    – Re...
Blood Urea Nitrogen BUN• Urea produced by breakdown of amino  acids - influenced by diet, dehydration,  and hemolysis• Nor...
Creatinine clearance• Creatinine is an end product of muscle  metabolism• Muscle mass is constant; creatinine is  constant...
• Creatinine clearance is an indirect  measure of GFR and renal blood flow• Creatinine is neither reabsorbed nor  secreted...
Diagnostic testing• Inulin clearance - not absorbed or  secreted = GFR• PAH – para-aminohippuric acid – not  absorbed ; ac...
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Renal structure and function

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Renal structure and function

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Renal structure and function

  1. 1. Renal Structure and Function 1
  2. 2. Kidneys• Paired• Retroperitoneal• Partially protected by the 11th and 12th ribs• Right slightly lower due to liver• Surrounded by renal capsule• Adipose capsule• Renal fascia 2
  3. 3. 3
  4. 4. 4
  5. 5. Anatomy• Hilum (hilus)• Renal artery and vein• Cortex• Medulla• Renal pyramids and renal papillae• Major and minor calyces• Renal Pelvis• Ureters 5
  6. 6. 6
  7. 7. • Ureters connect kidneys to urinary bladder• Urethra leads from bladder outside the body 7
  8. 8. 8
  9. 9. • Kidneys make up 1 % of body mass, but receive about 25% of cardiac output.• Kidney has two major functions: 1. Filtration of blood • Removes metabolic wastes from the body, esp. those containing nitrogen 9
  10. 10. 2. Regulation: Blood volume and composition Electrolytes Blood pH Blood pressure 10
  11. 11. Nephron• Functional unit of the kidney• Filtration, tubular reabsorption, tubular secretion• Renal corpuscle: – Glomerulus – capillaries – Glomerular or Bowman’s capsule 11
  12. 12. • Bowman’s capsule – Receives filtrate• Proximal convoluted tubule – Reabsorption of water and solutes• Nephron loop or Loop of Henle – Regulates concentration of urine• Distal convoluted tubule and Collecting duct • Reabsorption of water and electrolytes – ADH, aldosterone, ANP – Tubular secretion 12
  13. 13. 13
  14. 14. 14
  15. 15. 15
  16. 16. 16
  17. 17. Filtration• Renal corpuscle• Filtration membrane – Fenestrated endothelium of capillaries – Basement membrane of glomerulus – Slit membrane between pedicels of podocytes 17
  18. 18. Forces that influence filtration• Glomerular blood hydrostatic pressure• Opposing forces: – Plasma colloid osmotic pressure – Capsular hydrostatic pressure 18
  19. 19. 19
  20. 20. Glomerular Filtration Rate• Volume of plasma filtered / unit time• Approx. 180 L /day• Urine output is about 1- 2 L /day• About 99% of filtrate is reabsorbed 20
  21. 21. 21
  22. 22. GFR influenced by:• Blood pressure and blood flow• Obstruction to urine outflow• Loss of protein-free fluid• Hormonal regulation – Renin – angiotensin – Aldosterone – ADH – ANP 22
  23. 23. Juxtaglomerular apparatus• Juxtaglomerular cells lie in the wall of afferent arteriole• Macula densa in final portion of loop of Henle – monitor Na+ and Cl- conc. and water• Control blood flow into the glomerulus• Control glomerular filtration 23
  24. 24. 24
  25. 25. 25
  26. 26. Tubular reabsorption• Water, glucose, amino acids, urea, ions• Sodium diffuses into cell; actively pumped out – drawing water with it 26
  27. 27. 27
  28. 28. 28
  29. 29. • In addition to reabsorption, also have tubular secretion – substances move from peritubular capillaries into tubules – a second chance to remove substances from blood. 29
  30. 30. 30
  31. 31. • By end of proximal tubule have reabsorbed:• 60- 70% of water and sodium• about 100% of glucose and amino acids• 90 % of K+, bicarb, Ca++, uric acid• Transport maximum – maximum amount of a substance that can be absorbed per unit time• Renal threshold – plasma conc. of a substance at which it exceeds Tm. 31
  32. 32. Loop of Henle• Responsible for producing a concentrated urine by forming a concentration gradient within the medulla of kidney.• When ADH is present, water is reabsorbed and urine is concentrated.• Counter-current multiplier 32
  33. 33. 33
  34. 34. Distal convoluted tubule and collecting ducts• What happens here depends on ADH• Aldosterone affects Na+ and K+• ADH – facultative water reabsorption• Parathyroid hormone – increases Ca++ reabsorption 34
  35. 35. 35
  36. 36. Distal convoluted tubule and collecting ducts• Tubular secretion to rid body of substances: K+, H+, urea, ammonia, creatinine and certain drugs• Secretion of H+ helps maintain blood pH (can also reabsorb bicarb and generate new bicarb) 36
  37. 37. 37
  38. 38. Renal diagnostic procedures• Urinalysis is non-invasive and inexpensive• Normal properties are well known and easily measured 38
  39. 39. pH• Normally 4.8 – 8.0• Higher in alkalosis, lower in acidosis• Diabetes and starvation ↓ pH• Urinary infections ↑ pH – Proteus and pseudomonas are urea splitters 39
  40. 40. Specific gravity• Normal values 1.025 -1.032• High specific gravity can cause precipitation of solutes and formation of kidney stones• When tubules are damaged, urine specific gravity approaches that of glomerular filtrate – 1.010 – remains fixed = 2/3 of nephron mass has been lost 40
  41. 41. • Diabetes insipidus = 1.003• Diabetes mellitus = 1. 030• Emesis or fever = 1.040 41
  42. 42. Microscopic analysis• Red blood cells – should be few or none – Hematuria – large numbers of rbc’s in urine – Catheterization – Menstruation – Inflamed prostate gland – Cystitis or bladder stones 42
  43. 43. • Casts – precipitate from cells lining the renal tubules – Red cells – tubule bleeding – White cells – tubule inflammation – Epithelial cells – degeneration, necrosis of tubule cells 43
  44. 44. • Crystals – – Infection – Inflammation – stones 44
  45. 45. • White blood cells – Pyuria – Urinary tract infection• Bacteria 45
  46. 46. Substances not normally present in urine• Acetone• Bile, bilirubin• Glucose• Protein – albumin – Renal disease involving glomerulus 46
  47. 47. Blood Urea Nitrogen BUN• Urea produced by breakdown of amino acids - influenced by diet, dehydration, and hemolysis• Normal range 10-20 mg/ dL• If the GFR decreases due to renal disease or blockage, or decreased blood flow to kidney - BUN increases• General screen for abnormal renal function 47
  48. 48. Creatinine clearance• Creatinine is an end product of muscle metabolism• Muscle mass is constant; creatinine is constant• Normal 0.7 – 1.5 mg/ dL in plasma• Can then be compared to creatinine in urine over 24 hour period to determine clearance 48
  49. 49. • Creatinine clearance is an indirect measure of GFR and renal blood flow• Creatinine is neither reabsorbed nor secreted, just freely filtered.• Amount excreted = amount filtered• Useful to monitor changes in chronic renal function• Increases with trauma with massive muscle breakdown 49
  50. 50. Diagnostic testing• Inulin clearance - not absorbed or secreted = GFR• PAH – para-aminohippuric acid – not absorbed ; actively secreted = renal plasma flow 50
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