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Renal (CP) > 2 renal phys review > Flashcards

2 renal phys review Flashcards

1
Q

What are 5 major functions of the kidney?

A
  • excretion of metabolic waste products and foreign chemicals
  • regulation of arterial pressure
  • secretion, metabolism, and excretion of hormones
  • regulation of water, electrolyte, and acid-base balances
  • gluconeogenesis

**Main Role= control volume and composition of the bodily fluids

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2
Q

Describe the distribution and major contents of body fluids (ICF/ECF)

A
  • ICF
    • 2/3 of total body water
    • 40% of body weight
    • K, PO4, protein
  • ECF
    • 1/3 of total body water
    • 20% of body weight
    • Na, Cl, HCO3
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3
Q

What is the average osmolarity of the body fluids?

A

ECF and ICF average 280-300 mOsm/L

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4
Q

What are the forces causing filtration by glomerular capillaries?

A
  • Plasma
    • glomerular hydrostatic pressure (60 outward)
    • glomerular colloid osmotic pressure (32 inward)
  • Bowman’s capsule
    • hydrostatic pressure (18 into plasma)
    • NO osmotic pressure (proteins not filtered)
  • Ultrafiltration coefficient
    • hydraulic permeability
    • surface area of glomerular capillary membranes
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5
Q

What is the rate of plasma flow through afferent/efferent arterioles and a normal GFR?

A
  • afferent= 700 ml/min
  • GFR= 125 ml/min (~20% of efferent flow)
  • efferent= 575 ml/min
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6
Q

How does chronic kidney disease affect filtration?

A

Glomeruli become sclerotic/fibrotic and unable to filter. This decreases the surface area available for filtration, decreasing the ultrafiltration coefficient

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7
Q

Increasing renal perfusion pressure from 100 mmHg to 130 mmHg will most likely…

A

Increase urine flow rate

(at normal pressure variation, renal blood flow and GFR remain fairly constan)

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8
Q

What are the mechanisms of GFR/RBF autoregulation?

A
  • myogenic mechanism (in all vessels)
    • increased arterial pressure= increased stretch of vascular smooth muscle
    • stretch elicits contraction, elevating vascular resistance, and maintaining blood flow/GFR
    • F=P/R
  • tubuloglomerular feedback (unique to kidney)
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9
Q

Describe the structure of the juxtaglomerular apparatus

A

Na sensing cells in the macula densa communicate with juxtaglomerular cells in the afferent arteriole (contrict aff art when increased NaCl delivery to MD)

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10
Q

Describe the mechanism of macula densa feedback

A
  • elevated perfusion pressure, increases fluid filtration, increasing delivery of NaCl to the macula densa
  • elicits increased vascular resistance of the afferent arteriole, decreasing flow
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11
Q

Describe the hormonal control of GFR (vasoconstrictors/dilators)

A
  • vasoconstrictors (decrease GFR)
    • NE
    • epinephrine
    • endothelin
  • vasodilators (increase GFR)
    • endothelial derived NO
    • prostaglandins
  • Ang II= no change because it affects both afferent and efferent arterioles (decreases GFR at pathological levels)
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12
Q

What are the 3 layers of the kidney’s filtration barrier?

A
  1. capillary wall (700 A fenestrations)
  2. basement membrane (IV collagen)
  3. podocytes (40x140 A slit pores)

**barrier is negatively charged (most proteins are neg and therefore are not permeable)

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13
Q

What are the main functions of the proximal tubule?

A
  • iso-osmotic reabsorption
    • reabsorb 65% of Na, Cl, HCO3, and K
    • reabsorb an equal amount of water!
  • reabsorb essentially all the filtered glucose and AAs
  • secrete organic acids, bases, and H ions
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14
Q

What diuretic works on the proximal tubule?

A

Carbonic anhydrase inhibitors (acetazolamide)

**Inhibits H secretion and HCO3- reabsorption (makes urine more basic, inhibits Na/H exchanger on apical membrane and decrease Na reabsorption)

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15
Q

Describe the absorption of various substances across the proximal tubule

A
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16
Q

What is the main function of the thin descending loop of Henle?

A

Reabsorption of water secondary to the cortical-medullary osmotic gradient

17
Q

What are the main functions of the thin ascending loop of henle?

A
  • passive reabsorption of sodium, dilution of tubular fluid
  • secretion of urea
  • IMPERMEABLE to water!
18
Q

What are the main functions of the thick ascending loop of henle?

A
  • reabsorbs 25% of filtered Na (Na/K/2Cl transporter)
  • lumen positive potential (mostly from reabsorption of K+) drives paracellular reabsorption of Na, K, Mg, and Ca
  • impermeable to water (dilutes tubular fluid)
19
Q

What diuretic works on the thick ascending limb of henle?

A

Loop diuretics (furosemide, bumetanide, ethacrynic acid)

**inhibit Na/K/2Cl transporter, inhibiting ion reabsorption

20
Q

What are the main functions of the early distal tubule?

A
  • reabsorbs Na, Cl, Ca, and Mg
    • Na/Cl symporter on apical membrane
  • IMPERMEABLE to water
21
Q

What diuretics work on the early distal tubule?

A

Thiazide diuretics

**inhibit Na and Cl reabsorption

22
Q

What are the main functions of the principle cells of the late distal tubule/collecting duct?

A
  • reabsorb Na, secrete K
  • regulated by aldosterone
  • water permeability regulated by ADH
23
Q

What diuretics work in the principle cells (late distal tubule, collecting duct)?

A
  • Aldosterone antagonists
    • aka K sparing diuretics
    • inhibit normal action of aldosterone (increasing Na+/K+ ATPase pump at the basolateral membrane and ENaC at the apical membrane)
    • results in decreased reabsorption of Na
  • Na channel blockers also work on this area
    • amiloride, triamterene
    • inhibit ENaC (K secretion, Na reabsorption)
24
Q

What are the main functions of the medullary collecting duct?

A
  • reabsorbs Na (similar to principle cells)
  • ADH stimulate water reabsorption
  • urea reabsorption
25
Q

Where does aldosterone act? What is its function?

A
  • primarily in the principal cells of the late distal tubule/collecting duct
  • increases Na reabsorption, increases K secretion
26
Q

Where does angiotensin II act? What is its function?

A
  • primarily in the proximal tubule
  • increases Na and water reabsorption, increases H secretion
27
Q

Where does ADH act? What is its function?

A
  • principle cells of the late distal tubule/collecting duct, and inner medullary collecting duct
  • increases water reabsorption
28
Q

Where does ANP act? What is its function?

A
  • distal tubule and collecting duct
  • decreases Na reabsorption
29
Q

Where does PTH act? What is its function?

A
  • proximal tubule, decreasing phosphate reabsorption
  • thick ascending loop of henle/distal tubule, increasing Ca reabsorption

Renal (CP) (16 decks)

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