Renal 1

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Renal 1
2013-11-10 15:45:33
BC Nurse Anesthesia

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  1. Ureters
    • transport urine from kidneys to the bladder
    • muscular tubes
  2. Bladder
    • Hollow and viscous
    • very distensible
    • temporary urine storage
    • muscle contraction is required to empty the bladder
  3. Urethra
    transports urine from the bladder out of the body
  4. Why does the right kidney sit lower than the left
    right kidney is crowded by the liver
  5. renal hilus
    • on the medial (concave) side of the kidney
    • where all vessels, nerves, lymph, and ureters enter and exit the body
  6. renal capsule
    fibrous capsule that helps to prevent kidney infection
  7. adipose capsule
    adipose tissue that cushions the kidney and helps to connect it to the abdominal wall
  8. Kidney wt
    • 150 g
    • about the size of a fist
  9. 3 major areas of the kidney
    • cortex (outer)
    • medulla (inner)
    • -contains renal pyramids that are separated by columns
    • pelvis- flat funnel shaped tube lateral to the hilus
  10. renal lobe
    medullary pyramid and its surrounding capsule
  11. Purpose of the renal pelvis
    collects urine, urine flows down ureters and into the bladder
  12. Renal blood flow
    22% of CO or 1100 ml / min
  13. Major path of renal blood flow
    renal artery (to smaller branches) to afferent arterioles, glomerulus, efferent arterioles, peritubular capillaries
  14. 2 capillary beds of the kidneys
    • glomerular and peritubular
    • separated by efferent arterioles which regulate the hydrostatic pressure in both sets of capillaries
  15. Venous drainage of the kidneys
    peritubular capillaries drain into the venous system and end in the renal vein
  16. T or F, the kidney can control the hydrostatic pressure in both capillary beds by altering the resistance.  This changes GFR and tubular reabsorption to maintain homeostasis.
  17. Nephron
    -what is it?
    -how many?
    • functional unit of the nephron
    • 1 million / kidney
    • not regenerative

    we lose 10% / decade after age 40
  18. T or F, we have exactly the amount of nephrons that we need?
    F, we have more than we need.  So as we age and lose nephrons, others pick up the slack
  19. Nephron parts
    • glomerulus
    • tuft of glomerular capillaries
    • tubule
  20. renal corpuscle
    • glomerulus and bowman's capsule only
    • or nephron minus the tubules
  21. bowman's capsule
    collects tubular fluid (eventually urine) that gets filtered from glomerular capillaries
  22. Path of tubular fluid in the nephron
    bowman's capsule to renal tubules (PCT to LoH to distal tubule) then to collecting ducts and finally to the renal pelvis
  23. What's the difference between the cortical and juxtaglomerular nephrons?
    • Difference is how deep the LoH goes into the kidney
    • Cortical have short LoH (only go a little way into the medulla)
    • JG- longer LoH (go deep into the medulla)
  24. What percent of nephrons are juxtaglomerular?
  25. What is the significant of the juxtaglomerular nephrons?
    • important for generating an osmotic gradient in the medulla
    • this becomes responsible for water reabsorption
    • creates a dilute or concentrating urine depending on our needs
  26. Vasarecta
    • juxtaglomerular nephron blood supply
    • long efferent arterioles that go down into outer medulla and divide into special peritubular capillaries (vasarecta)
    • lie side by side with the LoH
  27. 3 layers of the glomerular capillary
    • Inner to outer:
    • endothelium
    • basement membrane
    • epithelium (podocytes)- specific to glomerular capillary
  28. What's the purpose of having 3 layers of the glomerular capillary?
    Ability to filter more water and solutes than the normal 2 layer membrane
  29. Does the glomerular layer allow proteins to pass?  Why or why not?
    No, 1) they are too large, 2) both the proteins and the membrane layers have negative charges which repel each other
  30. type of junctions / pore of the epithelial layer
    slit junctions or slit pores (may be labeled as tight junctions in some sources)
  31. Where are mesangial cells found?
    • found in-between and within the loops of the glomerular capillaries
    • cell type, not a layer
  32. Purpose of the mesangial cells
    • Phagocyte- remove trapped foreign material from the basement membrane
    • Myofilaments- can contract to reduce surface area available for filtration?
  33. Kidney functions
    • excretion of metabolic waste products
    • regulate water and lytes
    • regulate osmolarity (LoH and vasarecta)
    • regulate acid-base
    • regulate BP (renin) 
    • secretion, metab, and excretion of erythropoietin to stimulate RBC production
    • gluconeogenesis
    • activation of vitamin D
  34. Glomerular filtration
    • blood to urine
    • filtering of plasma like fluid thru glomerular capillaries thru Bowman's capsule to the renal tubules
  35. What substances get filtered by the glomerulus?
    Most substances in the plasma with the exception of proteins and cells
  36. Tubular reabsorption
    • urine to blood
    • substances get reabsorbed from the tubular fluid back into the blood thru the peritubular capillaries
  37. Tubular secretion
    • blood to urine
    • substances get actively secreted from the blood into the tubular fluid for excretion
  38. T or F, excretion = filtration - reabsorption - secretion
    • F!
    • Excretion = filtration - reabsorption + secretion
  39. What 2 ions tend to be secreted by the tubules?
    H and K
  40. What is the goal of glomerular filtration?
    Eliminate waste products while retaining water and important electrolytes to obtain ideal ECF composition
  41. What waste products from metabolism get filtered and eliminated?
    • Urea- from AA
    • Creatinine- from muscle creatine
    • Uric acid- from nucleic acids
    • Bilirubin- from Hbg
  42. Are electrolytes most excreted or reabsorbed?
  43. Are AA and glucose excreted or reabsorbed?
    • Reabsorbed
    • Provided their levels are below the threshold, they won't spill into the urine
  44. What is the composition of the glomerular filtrate?
    Like plasma, but without plasma proteins and cells
  45. GFR
    • 180 L/ day
    • 125 ml/ min
  46. What determines GFR?
    • Opposing forces: hydrostatic pressure (pushing) and colloid osmotic pressure (pulling) in 2 areas:
    • glomerular capillaries
    • Bowman's capsule
  47. What is the net filtration pressure of GFR?  What factors determine this?
    • Net filtration pressure = 10 mmHg
    • Net filtration pressure =
    • glomerular hydrostatic pressure (60 mmHg)
    • - Bowman's capsule pressure (18 mmHg)
    • -glomerular colloid osmotic pressure (32 mmHg)
  48. Why is the colloid osmotic pressure of Bowman's capsule not a factor in GFR?
    There is no protein
  49. What is the filtration coefficient as it relates to GFR?
    • permeability x surface area available for filtration
    • sounds like Fick's Law
  50. What is the filtration fraction?
    How is it calculated?
    fraction of the plasma flowing thru the glomerulus that actually does get filtered

    FF= GFR / renal plasma flow= 22%
  51. How do we know that most of the plasma volume gets reabsorbed?
    • GFR = 180 L / day
    • but we don't urinate that much / day!!
  52. T or F, the permeability of the glomerular capillaries is 10X greater than that of other capillaries?
    F, 50X greater
  53. What size substances are filtered by the glomerulus?  
    What size are not filtered?
    • Freely filtered- molecules with diameters < 4nm, (lytes and glucose)
    • Not filtered- >8nm (proteins)
  54. What factors affect what gets filtered by the glomerulus?
    • Size of the molecule
    • Charge
    • Size of the capillary bed
  55. How do the mesangial cells affect the size of the capillary bed?
    They have myofilaments that can contract to decrease the surface area available for filtration
  56. What substances would cause contraction of the mesangial cells to decrease the SA area for filtration?
    What would cause relaxation and increase the SA?
    • Contraction: angio2, vasopressin, NE
    • Relaxation: dopamine
  57. How does the charge of the glomerular capillaries affect filtration?  Is this more or less important than the size of the molecules?
    • Basement membrane has a negative charge and so does albumin, hence it is not filtered
    • Charge has a greater effect than size
  58. What factors affect GFR?
    • Renal blood flow
    • Glomerular capillary hydrostatic pressure
    • Bowman's capsule hydrostatic pressure
    • Glomerular capillary osmotic pressure
    • Changes in filtration coefficient
  59. Formula for calculation of renal blood flow
    • RBF = 
    • renal artery pressure - renal vein pressure
    • divided by
    • renal vascular resistance

    Ohm's Law
  60. What is renal artery pressure?
    What is renal venous pressure?
    • Renal artery pressure = systemic arterial pressure
    • renal venous pressure= 3-4 mmHg
  61. What controls renal vascular rx?
    • SNS
    • hormones
    • main rx vessels are the afferent and efferent arterioles- contraction of either reduces RBF
    • rx is increased by decreased renal blood flow
  62. At what MAP does renal auto regulation occur?
    • 80-170 mmHg
    • in this range, RBF and GFR remain constant
  63. Why is RBF 10X than is required for kidney metabolism?
    To allow the kidneys to eliminate waste products
  64. How does the SNS affect renal blood flow and GFR?
    • activation causes VC of afferent and efferent arterioles
    • decreased RBF
    • decreased GFR
  65. How do NE, epi, and endothelin affect RBF and GFR?
    • Cause VC of afferent and efferent arterioles
    • Decreased RBF
    • Decreased GFR
  66. Where is renin secreted from?  What causes its secretion?
    • JGA
    • Decreased RBF (macula densa sense a decrease in Na and Cl)
  67. How does renin affect RBF and GFR?
    • Activates RAAS, angio 2 is produced
    • Angio2 preferentially constricts the efferent arteriole
    • GFR is increased
  68. How does ANP affect RBF and GFR?
    • VD
    • Released from atria in response to plasma volume expansion
    • increases glomerular hydrostatic pressure
    • Reabsorption of Na and water are inhibited
    • RBF and GFR are increased
  69. How do prostaglandins, bradykinin, and NO affect RBF and GFR?
    • They are all VD
    • RBF and GFR are increased
  70. What is the purpose of renal auto regulation?
    • Maintain O2 and nutrient delivery
    • Removal of waste products
  71. As RBF increases, what happens to GFR?
    It increases and vice versa
  72. How does the JGA help to maintain GFR?
    • Macula densa senses a decrease in Na and Cl (increased reabsorption of both due to decreased GFR)
    • 1) decreases rx in the afferent arterioles to increase glomerular hydrostatic pressure
    • 2) renin is released causing angio2 to be produced, causing an increase in efferent arteriolar rx
  73. What is the tubuloglomerular feedback mechanism?
    Provides feedback to both the afferent and efferent arterioles for auto regulation of the GFR when BP changes
  74. How does the tubuloglomerular feedback mechanism work?
    • Activated by decreased BP, decreased GFR and decreased flow at LoH
    • Decreased Na Cl concentration is sensed by macula densa (more time for reabsorption because of decreased flow), so...
    • renin and angio2 are released
    • net effect:
    • decreased rx of afferent arterioles
    • VC of efferent arterioles (angio 2)
    • that causes:
    • increased glomerular hydrostatic pressure
    • increased GFR
  75. What are 2 mechanisms for renal auto regulation?
    • tubuloglomerular feedback mechanism
    •  and 
    • myogenic mechanism
  76. How does the myogenic mechanism work to maintain renal blood flow?
    • smooth muscle of afferent arterioles contracts in response to stretching
    • due to contraction, rx is increased
    • decreased RBF
    • decreased GFR (back to normal)
  77. What happens to RBF with a MAP < 70 mmHg?  What about with a MAP < 40-50 mmHg?
    • <70 decreased RBF
    • <40-50 glomerular filtration stops
  78. How does increased glomerular capillary hydrostatic pressure effect GFR?
    It increases it
  79. What 3 factors affect glomerular capillary hydrostatic pressure?
    • Systemic BP
    • afferent arteriolar tone
    • efferent arteriolar tone
  80. If we increase systemic BP, how is glomerular capillary hydrostatic pressure affected?
    It is also increased
  81. What effect does decreased afferent arteriolar tone (vasodilation) have on GFR?
    • Increased blood flow
    • Increased glomerular capillary hydrostatic pressure
    • Increased GFR
  82. What effect does increased afferent arteriolar tone (vasoconstriction) have on GFR?
    • Less blood flow
    • Decreased glomerular capillary hydrostatic pressure
    • Decreased GFR
  83. What effect does increased efferent arteriolar tone (vasoconstriction) have on GFR?
    • Rx to outflow
    • Increased glomerular capillary hydrostatic pressure
    • GRF is increased, to a point (as long as blood flow doesn't back up and decrease renal blood flow)
  84. What would cause an increase in Bowman's capsule hydrostatic pressure?
    • ureteral calculi
    • pushes back into the glomerular capillaries
  85. What affect would an increase in Bowman's capsule hydrostatic pressure have on GFR?
    decreased GFR
  86. What would increase the glomerular capillary osmotic pressure?
    An increase in plasma protein concentration
  87. What effect would an increase in the glomerular capillary osmotic pressure have on GFR?
    • Plasma proteins pull fluid back into the glomerular capillaries 
    • This opposes filtration
    • Decreased GFR
  88. What does an increase in the filtration coefficient mean?  How does this affect GFR?
    • Increased SA or permeability to filtration
    • GFR is increased
  89. HTN and DM can cause thickening of the blood vessels, thus decreasing the effective SA available for filtration- how does this effect GFR?
    GFR is decreased
  90. How does acute HTN affect GFR?
  91. What effect do chronic uncontrolled HTN, DM, kidney stones, renal artery stenosis, and SNS stimulation have on GFR?
    GRF is decreased
  92. How do ACEI effect GFR?
    • Decrease in efferent arteriolar rx
    • (angio 2's effect of preferential VC of the efferent arteriole is blocked)
    • This causes decreased glomerular capillary hydrostatic pressure
    • Decreased GFR
  93. Describe the path of the glomerular filtrate
    • Filtered from the glomerular capillaries
    • Bowman's capsule
    • proximal tubule (cortex)
    • LoH (dips into medulla)
    • distal tubule
    • collecting duct
    • renal pelvis
  94. What is urine composed of (reabsorption, secretion, filtrate)?
    Urine = glomerular filtration - tubular reabsorption + tubular secretion
  95. In what ways can tubular reabsorption occur?
    • active transport (Na/K/ATPase pump)
    • co-transport with Na+
    • osmosis (water)
  96. What substances undergo co-transport with Na+?  
    What direction are they traveling in?
    • Glucose
    • AA
    • organic acids

  97. What is counter transport?
    • A substance going in the opposite direction as Na+
    • Na+ is reabsorbed in exchange for H+ being excreted
  98. Primary active transport
    • coupled directly with the energy source
    • Na+ alone
  99. Secondary active transport
    • AKA co-transport with Na+
    • coupled indirectly to an energy source
    • Active only because the concentration gradient for Na+ set up by Na/K/ATPase pump
  100. What is the major function of the PCT?
    • Na+ reabsorption (about 2/3's occurs here)
    • enhanced by angio 2 and NE
  101. Glucose secondary active transport
    • Na+ concentration gradient set up by the Na/K/ATPase pump allows Na+ to travel down it's concentration gradient (tubular fluid to ISF)
    • glucose travels with the sodium and is reabsorbed
    • AA are reabsorbed this way as well
  102. How is water reabsorbed?
    • Passively by osmosis
    • can only move if the membrane is permeable to it, regardless of the concentration gradient
  103. Solvent drag
    • Water often moves with Na+
    • As water moves by osmosis, it can carry solutes with it
  104. Describe the permeability of the proximal tubule to water and ions
    highly permeable
  105. Describe the permeability of the ascending LoH to water
  106. Describe the permeability of the distal tubules, collecting tubules, and collecting ducts to water 
    • varies
    • dependent on ADH and insertion of aquaporins
  107. Where does the PCT receive filtrate from?
    How much Na and water is reabsorbed?
    • Bowman's capsule
    • 65%
  108. Why is the PCT well suited for active transport ?
    • Lots of mitochondria and carrier proteins
    • Na, water, and glucose and AA get reabsorbed
  109. What does the PCT secrete?
    organic acids, H+ ions, bases, bile salts, catecholamines
  110. LoH: thin descending's permeability to water
    • very water permeable
    • moderate permeability to solutes
    • simple diffusion (few mitochondria)
  111. LoH: thin and thick ascending's permeability to water
    • impermeable
    • key to generating concentrated urine
  112. T or F, the thick ascending limb of the LoH will reabsorb 25% of filtered Na, Cl, K, and large amts of Ca, bicarb, and Mg
  113. Loop diuretic site of action
    thick ascending limb of the LoH
  114. In what part of the tubules is the JGA located?
    first part of the distal tubule
  115. What does the diluting segment of the early distal tubule reabsorb?
    Is it permeable to water?
    • Most ions
    • Water impermeable
  116. What is the site of action of thiazide diuretics?
    early distal tubule
  117. Late distal tubule- what is reabsorbed?  secreted?
    • reabsorbed- Na
    • water permeability controlled by ADH
    • secreted- K
  118. What is the site of action of the K sparing diuretics?
    late distal tubule
  119. What is the final site for processing urine?
    medullary collecting duct
  120. In the medullary collecting duct how is permeability to water controlled?
    by ADH
  121. Are the collecting ducts permeable to urea?  Why do we care?
    • Yes, unique b/c urea in the tubular fluid can be reabsorbed
    • urea increases the osmolarity of the interstitial fluid in the medulla, important in making a concentrating urine
  122. How are the collecting ducts involved in acid base regulation?
    Secretes H+ against a concentration gradient
  123. How does increased BP affect reabsorption?
    it's decreased
  124. How does an increase in plasma proteins effect colloid osmotic pressure?  reabsorption?
    • increased COP
    • increased reabsorption
  125. How do aldosterone and angiotensin 2 affect Na and water reabsorption?
  126. How does ADH affect Na and water reabsorption?
  127. How does ANP affect Na reabsorption?
  128. How does PTH affect phos and ca reabsorption?
    • decreased phos reabsorption
    • increased ca reabsorption