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Renal Exam > Renal Physiology > Flashcards

Renal Physiology Flashcards

1
Q

What are the biggest risk factors for Chronic kidney disease?

A
  1. DM
  2. Age > 65 y/o
  3. Ethnicity
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2
Q

Define acute kidney injury.

A

Sudden, temporary but sometimes fatal loss of kidney function

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3
Q

Define Chronic kidney disease.

A

Any condition that decreases kidney function over a period of time (typically measured by glomerular filtration rate, GFR)

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4
Q

Define end-stage renal disease.

A

Total and permanent kidney failure

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5
Q

What are the consequences of renal failure in the following?

  1. HTN
  2. Metabolic acidosis
  3. Muscle weakness
  4. Osteoporosis
  5. Anemia
  6. CNS, PNS, autonomic dysfunction
A
  1. HTN: Kidneys responsible
  2. Metabolic acidosis: Regulating hydrogen ions and absorbing bicarbonate
  3. Muscle weakness: Excreting Ca/K/Na
  4. Osteoporosis: Losing Ca in urine; kidneys make vitamin D
  5. Anemia: Kidneys are not making erythropoietin = EPO
  6. An increase in UREA which is toxic to nerves. Results in demyelineation.
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6
Q

How do you control BP?

A
  1. Lifestyle mods
    a. eat a low Na diet
    b. DASH diet
    c. Aerobic Exercise
    d. No smoking
    e. moderate to low alcohol intake
  2. Meds
    a. antihypertensives
    i. Beta blockers
    ii. ACE inhibitors
    iii. CCB
    iv. Diuretics
    v. Vasodilators
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7
Q

How do you control anemia?

A

Exogenous EPO

  1. Procrit
  2. Epogen
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8
Q

When do you use dialysis?

A

When GFR is 15% or below

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9
Q

What can exercise training in adults with CKD do?

A
  1. Improve BP control and lipid profiles (only HDLs)
  2. Increase GFR
  3. Improve glucose metabolism (helps DM)
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10
Q

Why is peritoneal dialysis preferred?

A
  1. Less expensive

2. SAFER

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11
Q

Define arteriovenous fistula for dialysis.

A

Surgically-created connection between an artery and a vein that makes needle placements easier.
Takes ~6 wks to heal and can be use for years.

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12
Q

What are precautions for the arm with an AV fistula?

A
  1. No BP
  2. Keep the port clean
  3. No Heavy lifting
  4. Do not sleep with arm under head
    • *Big Risk of Edema
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13
Q

What are the 2 distinct regions of the kidneys?

A
  1. Outer cortex - many capillaries
  2. Medulla
    i. pyramid contains minor calyces that form major calyx
    ii. major calyces unite to form renal pelvis
    iii. urine collected in pelvis is transported to ureter
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14
Q

What do kidneys do?

A
  1. Regulate ECF volume through urine formation
  2. Regulate blood plasma volume and thus regulates BP
  3. Regulates concentration of waste products in blood (primary UREA)
  4. Regulate concentration of many electrolytes (Na, K, HCO, etc)
  5. Regulate concentration of Hydrogen ions
  6. Secrete EPO and thus controls RBC production
  7. Eliminates drugs/foreign chemicals
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15
Q

What is a nephron?

A

Urinary tubules and associated blood vessels

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16
Q

What are the types of nephrons?

A
  1. Cortical

2. Juxtamedullary

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17
Q

What are the parts of the urinary tubule?

A
  1. PCT
  2. Loop of Henle
  3. DCT
  4. Collecting duct
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18
Q

Between the types of nephrons, which is more important for kidney function and why?

A

Juxtamedullary nephrons.

Critical to produce concentrated urine and long loops of Henle

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19
Q

Define Osmosis.

A

The passive diffusion of water from hypotonic to hypertonic solution.
Water will passively follow actively propelled ions.

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20
Q

What is the function of afferent arteriole?

A

Delivers blood into the glomeruli

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21
Q

What is the glomerulus?

A

It is a capillary network that produces filtrate that enters urinary tubules at the glomerular capsule.

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22
Q

What is the function of efferent arteriole?

A

Delivers blood FROM glomeruli to peritubular capillaries

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23
Q

What is the peritubular capillaries of the juxtameduallary nephrons’ specialization?

A

VASA RECTA, which are critical for production of concentrated urine

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24
Q

What is Bowman’s capsule?

A

It surrounds the glomerulus and this is where glomerular filtration occurs. The filtrate passes into the urinary space

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25
Q

What must the blood cross to get from the glomerulus to Bowman’s capsule?

A

Blood must cross the glomerular filtration membrane

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26
Q

What are the components that compromise the GFM

A
  1. Capillary endothelium
  2. Basement membrane
  3. Foot processes of podocytes of glomerular capsule
27
Q

Within the GFM, what prevents filtrates from being filtered in?

A
  1. Endothelial cells of glomerular capillaries

2. Basement membrane

28
Q

What do the pores of the capillary endothelium not let through?

A

Formed elements

  1. RBC
  2. WBC
  3. Platelets
29
Q

Describe the basement membrane.

A

It is a thin glycoprotein layer that is negatively charged. It does not allow plasma proteins to pass through (because they too are negative)

  1. Fibrinogen
  2. Albumin
  3. Angiotensinogen
30
Q

Define the podocytes of Bowman’s capsule.

A

Spaces between foot pedicels form small filtration slits that allow filtered molecules to enter interior of Bowman’s capsules

31
Q

The fluid that enters the glomerular capsule is called…

A

Ultrafiltrate.

32
Q

How is an ultrafiltrate formed?

A

Formed under the hydrostatic pressure of blood

33
Q

Define GFR.

A

Glomerular filtration rate. The volume of filtrate removed from blood each minute.

34
Q

What is average of the GFR?

A

Averages 180 L/day!

35
Q

What is the best test to measure kidney function and determine stage of kidney disease?

A

a GFR test, which is calculated by blood creatinine levels.

36
Q

At the beginning of glomerular capillary, what is the net filtration pressure?

A

+16 mmHG.

37
Q

At the end of glomerular capillary, what is the net filtration pressure and why?

A

0 mmHG. Due to the oncotic pressure increasing at the end of the capillary. Blood/plasma is more concentrated

38
Q

Why does GFR need to be regulated?

A
  1. Need to be high enough to filter out toxins

2. Not so high that you lose blood volume.

39
Q

How is the GFR regulated?

A

Vasoconstriction or vasodilation of afferent arterioles affects the rate of blood flow to the glomerulus, which affects GFR

40
Q

Which systems regulate GFR?

A
  1. Sympathetic nervous system
  2. Autoregulation
  3. Renin-angiotensin II system
    * *Angiotensin II stabilizes GFR (by preventing decreases)
41
Q

What causes vasoconstriction of afferent arterioles and what is the result?

A

SNS activiation.

  1. It will decrease glomerular capillary hydrostatic pressure.
  2. Decrease urine output
42
Q

Define autoregulation.

A

The ability of kidneys to maintain a relatively constant GFR under widely changing BPs (MAPS ranging 70-180 mmHG)

This is the way to protect kidneys and makes sure GFR works properly.

43
Q

How does autoregulation occur?

A
  1. Effects of locally-produced chemicals on afferent arterioles
    a. When BP decreases, AA vasoldilate = increase GFR
    b. When BP increases, AA vasoconstrict = decrease GFR
  2. Tubuloglomerular feedback from macula densa
44
Q

** Define Filtration.

A

Water & Solutes that pass from blood plasma to inside of glomerular capsule and tubules
(Blood to Tubules)

45
Q

**Define Reabsorption

A

Return of water and filtered molecules from tubules into blood
(Tubules to Interstitial Space to Blood)

46
Q

**Define Secretion

A

ACTIVE transport of substances from blood into tubules

Blood to Tubule

47
Q

**Define Excretion

A

Fluid and solutes that LEAVE the body

48
Q

Although 180 L/day of ultrafiltrate are produced/day, ONLY how much of urine is actually excreted?

A

1-2 L.

Most filtered solutes and water are returned back into peritubular capillaries

49
Q

What is the obligatory water loss amount and for what?

A

Minimum of 400 ml/day of urine IS NECESSARY to excrete metabolic wastes

50
Q

What happens at the proximal convoluted tubule?

A

~65% of the salt and water that enter the glomerular capsule is REABSORBED across the PCT and returned to plasma

51
Q

How is it that fluid in PCT is ~1/3 of original volume, but is still isosmotic with plasma?

A

Active Na transport and osmosis

52
Q

Explain reabsorption in proximal tubule.

A

Na/K ATPase located in sides of cell membrane that creates gradient for Na diffusion across apical membrane.
Na/K ATPase extrudes Na. Na gradient causes Na diffusion INTO cell.
CI follows electrical gradient into interstitial fluid and water follows by osmosis

53
Q

Is reabsorption at PCT subject to hormonal regulation?

A

NO it is not subjected to hormonal regulation. Reabsorption here is CONSTANT

54
Q

How does the proximal tubule reabsorb glucose and amino acids?

A

By secondary active transport (cotransporters)

55
Q

What is the result of cotransporter saturation?

A
  1. Glycosuria: Glucose in urine
    This occurs when plasma glucose concentration is above 180 mg/dl.
    This is a clinical sign of DM
56
Q

How are the interstitial fluid surrounding the tubules remain hypertonic?

A

This is done by the long loops of Henle in the juxtameduallary nephrons

57
Q

Explain the countercurrent multiplier system

A
  1. Active Na extrusion from ascending limb makes surrounding fluid more concentrated which causes
  2. Water movement out of descending limb via osmosis
  3. Tubular fluid increases in concentration as surrounding interstitial fluid becomes more concentrated.
  4. Fluid volume decreases along tubule, causing higher Na in ascending limb
  5. Concentration of urine is multiplied because descneding limbis permeable to water (and impermeable to NaCl)
58
Q

What is the role of the VASA RECTA in countercurrent multiplier system?

A

It traps salt and urea within the interstitial fluid of the renal medulla and transports water out of renal medulla.

59
Q

What is UREA?

A

This contributes to total osmolality of interstitial fluid.

Ascending limb of LH and Collecting ducts are permeable to it. AND urea diffuses out of them as well.

60
Q

When do you call it URINE?

A

You can call it URINE when it gets to the CALYX. Before this, it is UREA

61
Q

What are the functions of the collecting ducts?

A
  1. Reabsorption of Na

2. Secretion of K

62
Q

How is the rate of water movement in the collecting ducts determined?

A

By the number of aquaporins in cell membrane

63
Q

What does the permeability to water from the collecting ducts depend on?

A

It depends on the presence of ADH.

64
Q

Briefly describe the mechanism of ADH in the collecting ducts.

A

ADH binds to V2 receptors on CD cells, incorporating aquaporins into cell membrane and the result of this are that CD cells are permeable to water so water can be reabsorbed.

Renal Exam (2 decks)

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