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Physiology > Ch 25: Urinary Part 2 > Flashcards

Ch 25: Urinary Part 2 Flashcards

1
Q

How much fluid is processed by the kidneys daily?

A

180 L

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2
Q

What are the three processes in urine formation?

A
  1. Glomerular filtration
  2. Tubular reabsorption
  3. Tubular secretion
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3
Q

What is the purpose for glomerular filtration?

A

Produces cell and protein free filtrate

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4
Q

What is the purpose of tubular reabsorption?

A

Selectively returns 99% of substances from filtrate to blood in renal tubules and collecting ducts

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5
Q

What is the purpose of tubular secretion?

A

Selectively moves substances from blood to filtrate in renal tubules and collecting ducts

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6
Q

How many times does plasma volume get filtered?

A

60

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7
Q

What is filtrate made out of?

A

Blood plasma minus proteins

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8
Q

What is urine made of?

A
  1. <1% of original filtrate
  2. Metabolic wastes and unneeded substances
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9
Q

What type of process is glomerular filtration?

A

Passive process

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10
Q

What kind of pressure is used in glomerular filtration?

A

Hydrostatic to where fluids and solutes are forced through a filtration membrane

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11
Q

What is the filtration membrane located?

A

Between blood and interior of glomerular capsule

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12
Q

What size are the particles that pass through the filtration membrane?

A

3nm

Water, glucose, aa, waster

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13
Q

Why should plasma proteins remain in the blood?

A
  1. Maintain colloid osmotic pressure
  2. Prevents loss of all water to capsular space
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14
Q

What happens if proteins are found in the filtrate?

A

Membrane problems

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15
Q

What is the outward pressures that promote filtrate filtration?

A

Hydrostatic pressure in glomerular capillaries = Glomerular blood pressure

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16
Q

What is glomerular blood pressure?

A
  1. Chief force pushing water, solutes out of blood
  2. 55mmHg
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17
Q

Why is the glomerular bp high?

A

Efferent arteriole is high resistance vessel with diameter smaller than afferent arteriole

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18
Q

What is the inward pressures that promote filtrate filtration?

A
  1. Hydrostatic pressure in capsular space
  2. Colloid osmotic pressure in capillaries
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19
Q

What is Hydrostatic pressure in capsular space?

A

Pressure of filtrate in capsule 15mmHg

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20
Q

What is Colloid osmotic pressure in capillaries?

A

Pull of proteins in blood 30mmHg

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21
Q

What is net filtration pressure?

A

The difference of forces going out and in of the glomerulus

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22
Q

What is the purpose of net filtration pressure?

A

Responsible for filtrate formation

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23
Q

What controls net filtration pressure?

A

Glomerular filtration rate

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24
Q

How much is the glomerular filtration rate (GFR)?

A

120-125mL/min

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25
Q

What factors are directly proportional to GFR?

A
  1. NFP
  2. Total surface area available for filtration
  3. Filtration membrane permeability
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26
Q

Why is important for GFR to remain constant?

A

Allows kidneys to make filtrate and maintain extracellular homeostasis

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27
Q

How does GFR affect systemic blood pressure?

A

Increase in GFR → Increased urine output → decrease BP

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28
Q

What is difference between intrinsic and extrinsic control of GFR?

A
  1. Intrinsic: Maintain GFR in kidneys
  2. Extrinsic: Maintains systemic BP
29
Q

What is intrinsic controls?

A
  1. Act locally within kidneys to maintain GFR
  2. Maintains nearly constant GFR when MAP is 80-180mmHg
30
Q

What are the types of autoregulation?

A
  1. Myogenic mechanism
  2. Tubuloglomerular feedback mechanism
31
Q

What is the purpose of myogenic mechanism?

A
  1. Smooth muscle contracts when stretched
  2. As BP increases, muscle stretch constricting afferent arterioles → restricts blood flow into glomerulus
  3. Decrease in BP dilate afferent arterioles
  4. Helps maintain normal GFR despite fluctuations of BP
32
Q

What type of mechanism is Tubuloglomerular feedback?

A

Flow-dependent mechanism

33
Q

What does the Tubuloglomerular feedback mechanism achieve?

A
  1. GFR increase → increased filtrate flow rate → decrease reabsorption time → high filtrate NaCl levels → constriction of afferent arterioles → decrease in NFP and GFR → more time for NaCl reabsorption
  2. Opposite occurs with decreased GFR
34
Q

What is extrinsic controls?

A
  1. Nervous and endocrine mechanisms that maintain blood pressure; can negatively affect kidney function
  2. Takes precedence over intrinsic controls
35
Q

What occurs in extrinsic controls when at rest?

A
  1. Renal vessels dilate
  2. Intrinsic mechanisms prevail
36
Q

What occurs when extracellular fluid volume is extremely low?

A
  1. Norepinephrine released by SNS
  2. Epinephrine released by adrenal medulla
  3. Systemic vasodilation → increase BP
  4. Constriction of afferent arterioles → decrease in GFR → increased blood volume and pressure
37
Q

What are the 3 pathways of RAAS?

A
  1. Direct stimulation of granular cells by SNS
  2. Stimulation by activated macula densa cells when filtrate NaCl concentration low
  3. Reduced stretch of granular cells
38
Q

What controls intrinsic and extrinsic?

A

Glomerular hydrostatic pressure

39
Q

What is the PCT?

A

The site of most reabsorption

40
Q

What is reabsorbed in the PCT?

A
  1. All nutrients
  2. 65% Na+ and water
  3. Many ion
  4. All uric acid
  5. 1/2 urea
41
Q

What is the difference between the ascending and descending limb of the Nephron loop?

A
  1. A: H2O can’t leave, solutes can
  2. D: H2O can leave, solutes can’t
42
Q

What is the thin segment of the ascending limb?

A

Allows passive Na+ movement

43
Q

What is the thick segment of the descending limb?

A

Na+-K+-2Cl- symporter and Na+-H+ antiporter; some passes by paracellular route

44
Q

What hormone regulate reabsorption in the DCT and collecting duct?

A
  1. ADH: water
  2. Aldosterone: Na+
  3. ANP: Na+
  4. PTH: Ca2+
45
Q

What is the purpose of ADH for reabsorption?

A
  1. Released by posterior pituitary gland
  2. Causes principal cells of collecting ducts to insert aquaporins in apical membranes → increased water reabsorption
46
Q

What is the purpose of aldosterone for reabsorption?

A
  1. Targets collecting ducts (Principal cells) and distal DCT
  2. Promotes synthesis of apical Na+ and K+ channels, and basolateral Na+-K+ ATPases for Na+ reabsorption; water follows
  3. Increase BP, decrease K+ levels
47
Q

What is the purpose of ANP?

A

Reduces blood Na+ → decreased blood volume and blood pressure

48
Q

What releases ANP?

A

Cardiac atrial cells

49
Q

What is the purpose of PTH for reabsorption?

A

Acts on DCT to increase Ca2+ reabsorption

50
Q

What is selective transepithelial process?

A
  1. All organic nutrients reabsorbed
  2. Water and ion reabsorption hormonally regulated and adjusted
  3. Includes active and passive tubular reabsorption
51
Q

What are the routes of tubular reabsorption?

A
  1. Transcellular route
  2. Paracellular route
52
Q

What is involved with the transcellular route?

A
  1. Transport across the apical membrane
  2. Diffusion through the cytosol
  3. Transport across the basolateral membrane
  4. Movement through the interstitial fluid and into the capillary
53
Q

What is involved with the paracellular route?

A
  1. Movement through leaky tight junctions in PCT
  2. Movement through the interstial fluid into capillary
54
Q

What is the role of Na+ in tubular reabsorption?

A

Most abundant cation in filtrate

55
Q

Describe the transport of Na+ across the across basolateral membrane

A

Primary active transport out of tubule cell by Na+-K+ ATPase pump → peritubular capillaries

56
Q

Describe the transport of Na+ across the across apical membrane

A

Na+ passes through apical membrane by secondary active transport or facilitated diffusion mechanisms

57
Q

What is the importance of Na+ being reabsorbed by active transported?

A

Provides energy and means for reabsorbing most other substances

58
Q

How is an electrical gradient created?

A

Passive reabsorption of anions

59
Q

How is organic nutrients reabsorbed?

A

By secondary active transport that is cotransported with Na+

60
Q

Describe the creation of the osmotic gradient for water

A

Movement of Na+ and other solutes

61
Q

What aid water for osmosis?

A

Aquaporins

62
Q

What is the importance of aquaporins?

A
  1. Present in the PCT that provides obligatory water reabsorption
  2. Aquaporins inserted in collecting ducts only if ADH present → facultative water reabsorption
63
Q

How are solutes passively reabsorbed?

A

Solute concentration in filtrate increases water reabsorbed → concentration gradients for solutes → fat-soluble substances (ions and ureas) follow water into peritubular capillaries down concentration gradients

64
Q

What is the purpose of tubular secretion in the PCT?

A
  1. Disposes of substances (e.g., drugs) bound to plasma proteins
  2. Eliminates undesirable substances passively reabsorbed (e.g., urea and uric acid)
  3. Rids body of excess K+ (aldosterone effect)
  4. Controls blood pH by altering amounts of H+ or HCO3– in urine
65
Q

Describe the reabsorption of products by the PCT cells

A
  1. At the basolateral membrane, Na+ is pumped into the interstitial space by the Na+-K+ ATPase. Active Na+ transport creates concentration gradients that drive:
  2. Downhill Na+ entry at apical membrane
  3. Reabsorption of organic nutrients and certain ions by cotransport at the apical membrane
  4. Reabsorption of water by osmosis through aquaporins. Water reabsorption increases the concentration of the solutes that are left behind. These solutes can then be reabsorbed as they move down their gradients:
  5. Lipid-soluble substances diffuse by the transcellular route.
  6. Various ions (e.g., Cl−, Ca2+, K+) and urea diffuse by the paracellular route.
66
Q

What is transport maximum?

A

When carriers saturated, excess excreted in urine can be caused by hyperglycemia

67
Q

What determine the transport maximum of reabsorbed substances?

A

When carriers saturated, excess excreted in urine can be caused by hyperglycemia

68
Q

What determine the transport maximum of reabsorbed substances?

A

Number of carriers in renal tubules available

Physiology (22 decks)

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