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Physiology > Exam 4: Tubular Processing of Glomerular Filtrate > Flashcards

Exam 4: Tubular Processing of Glomerular Filtrate Flashcards

1
Q

What is the filtration of glucose like?

A

Freely

100% is reabsorbed

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2
Q

What is the filtration of amino acids like?

A

Freely

100% is reabsorbed

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3
Q

What is the filtration of protein like?

A

Limited

100% is reabsorbed

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4
Q

What is the filtration of bicarb like?

A

Freely

More than 99.9% reabsorbed, but variable in the small intestine

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5
Q

What is the filtration of sodium like?

A

Freely

99.4% is reabsorbed, moderately variable

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6
Q

What is the filtration of chloride like?

A

Freely

99.1% is reabsorbed, moderately variable

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7
Q

What is the filtration of potassium like?

A

Freely

87.8% is reabsorbed, highly variable

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8
Q

What is the filtration of urea like?

A

Freely

50% is reabsorbed, highly variable

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9
Q

What is the filtration of creatinine like?

A

Freely

0%

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10
Q

Why is the Na-K ATPase particularly important?

A

It provides a chemical gradient for the absorption of many solutes

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11
Q

What has a transport maximum in the tubules?

A

Glucose
Amino acids
Protein

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12
Q

What can glucosuria (increased glucose in the urine) be caused by?

A

Hyperglycemia

Normoglycemic glucosuria

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13
Q

What is hyperglycemia?

A

Increased glucose in the blood, as seen in diabetes mellitus or pituitary adenoma (Cushings disease), to a point that more glucose is filtered and presented to the tubular epithelium than there are transport molecules for reabsorption

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14
Q

What does normoglycemic glucosuria indicate?

A

Sick and injured tubular epithelium where there are a diminished number of transport molecules that can’t handle a normal glucose load

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15
Q

Describe the proximal tubule

A 
High cell surface area
High metabolic rate
65% of reabsorption of Na and H2O
Reabsorbs essentially all glucose and AA
Secrete organic acids and other waste products
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16
Q

What gives the proximal tubule a high metabolic rate?

A

Many mitochondria

High O2 consumption

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17
Q

What happens to Na as the total amount decreases throughout the proximal tubule?

A

The concentration does not decrease as water moves with Na, but the total volume decreases significantly

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18
Q

Describe the thin loop of henle

A

No brush border
Few mitochondria
Minimal metabolic activity

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19
Q

Describe the thin descending loop of henle

A

Very permeable to H2O with 20% being absorbed here

Renal medullary interstitial fluid hypertonicity is essential

20
Q

Describe the thin ascending loop of henle

A

Not permeable to H2O
Moderately permeable to urea, facilitated passive, moving into tubule
Slightly to moderately permeable to Na, but mostly passive

21
Q

Describe the thick ascending loop of henle

A 
Increased surface area
Increased mitochondria
High metabolic activity
Impermeable to H2O
Impermeable to urea
25% of Na, K, Cl absorbed, but H2O does not follow
22
Q

What happens to the filtrate in the thick ascending loop of henle?

A

It is becoming more dilute

23
Q

What decreases sodium reabsorption at the thick ascending limb of the loop of henle during dehydration?

A

Prostaglandin E2

24
Q

What increases sodium reabsorption? How?

A

Administration of NSAIDs

By decreasing PGE2

25
Q

What does the early distal tubule contain?

A

Macula densa

26
Q

Describe the early distal tubule

A

Impermeable to water
Impermeable to urea
Active reabsorption of Na, Cl, and other electrolytes

27
Q

What does the permeability to H2O in the late distal tubule and collecting duct depend on?

A

ADH

28
Q

What is the late distal tubule and collecting duct impermeable to?

A

Urea

29
Q

What is the permeability and absorption of Na partially dependent on in the late distal tubule and collecting duct?

A

Aldosterone and angiotensin

30
Q

What do principle cells secrete?

A

Potassium

31
Q

What do intercalated A cells secrete?

A

H+

32
Q

What begins at the late distal tubule and collecting duct?

A

Regulated reabsorption and/or secretion

33
Q

What are intercalated cells important for?

A

pH control

34
Q

What are intercalated cells able to utilize?

A

The Na concentration gradient created by the Na-K ATPase pump to move H+ out
K secreted by principle cells to enable an energy dependent K/H+ counter transport to pump H+ out against a larger concentration gradient

35
Q

How is hydrogen generated?

A

Within the cell via the action of carbonic anhydrase on water and CO2

36
Q

What is H2O permeability controlled by in the medullary collecting duct?

A

ADH

37
Q

What is the medullary collecting duct permeable to?

A

Urea

38
Q

What does the medullary collecting duct being permeable to urea help with?

A

Helping keep medullary tonicity high- both passive and facilitated

39
Q

What is the permeability to Na and K in the medullary collecting duct controlled by in the medullary collecting duct?

A

Aldosterone

40
Q

What hormones are involved in the tubular resorption regulation?

A

Angiotensin II
Aldosterone
ADH
Atrial natriuretic factor

41
Q

What does angiotensin II do?

A

Increase efferent arteriole constriction
Increases tubular Na resorption directly
Increase tubular Na resorption via increased aldosterone secretion

42
Q

What would proteinuria and glucosuria with a normal blood glucose indicate?

A

Tubulonephritis resulting in diminished total transport capacity of the tubular epithelial cells so even normal altered amounts of exceeded tubular transport threshold

43
Q

What would proteinuria without glucosuria most likely indicate?

A

Glomerulonephritis resulting in increased albumin presentation to the tubules exceeding transport threshold

44
Q

Why doesn’t glomerulonephritis result in increased glucose presentation to the tubules as it does protein?

A

Because the glomerulus does not present a barrier to the filtration of glucose to begin with

45
Q

What would increase peritubular capillary reabsorption?

A

Increased efferent arteriolar resistance

Increased peritubular capillary albumin concentration

Physiology (70 decks)

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