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Y1 Urinary System > Tubular Function > Flashcards

Tubular Function Flashcards

1
Q

What is osmolarity?

A

A measure of the solute concentration in a solution that depends on the number of dissolved solutes present

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2
Q

What is osmolarity dependent on?

A

Number of particles in a solution, not the nature of the particles.

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3
Q

How is osmolarity calculated?

A

Calculated by all the concentrations of different solutes added together measured in mmol/l and each ion counted separately

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4
Q

What is the normal plasma osmolarity?

A

285-295 mosmol/l

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5
Q

What is the normal urine osmolarity?

A

50-1200mosmol/l

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6
Q

How can molecules be passively transported through the kidneys? What is the rate and solute concentration relationship using these forms of transport?

A

Protein independent transport - lipophilic molecules have a linear rate to solute conc relationship
Protein dependent transport - hydrophilic molecules has a curved rate to solute conc

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7
Q

What does secretion do in tubular functions?

A

Moves substances from peritubular capillaries to tubular lumen, constituting a pathway into the tubule.

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8
Q

How can secretion occur in the tubules

A

Diffusion

Transcellular mediated transport

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9
Q

What are the most important substances secreted in the tubules?

A

H+ and K+

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10
Q

What drugs are secreted in the tubules?

A

Choline
Creatine
Penicillin + others

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11
Q

Where are most solutes reabsorbed in the kidney nephron thingys, what percentage is that?

A

Proximal convoluted tubule - 60-70%
100% glucose
65% Na
90% bicarb

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12
Q

What drugs regulate collecting duct absorption?

A

Aldosterone and vasopressin

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13
Q

What is found in the inner medulla of the kidney?

A

Loop of henle thin descending limb

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14
Q

What is found in the outer medulla of the kidney?

A

Loop of Henle thick ascending limb

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15
Q

What is found in the cortex of the kidney?

A

Proximal and distal convoluted tubules
Glomerulus
Collecting duct

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16
Q

What happens in the basolateral membrane?

A

Na/K pump keeps intracellular Na low and K high

Large conc and electrical gradients favour Na movements into the cell - occurs in most nephron segments

17
Q

What happens in the early PCT?

A

Na+ entry down a large electrochemical gradient can bring about the uphill entry of glucose and aas and exit of H+
Carbonic anhydrase activity leads to Na+ reabsorption and increased urinary activity

18
Q

What is passively reabsorbed in the PCT?

A

Urea

Water

19
Q

What is actively reabsorbed in the PCT?

A 
Glucose
Amino acids
Sodium
Potassium
Calcium
Vit C
Uric acid
20
Q

Why is a net secretion by the PCT important?

A

It is a route of excretion for some substances

Some drugs enter the tubular fluid here and act further down the nephron

21
Q

What kind of epithelium does the descending loop of henle have? What happens here?

A

Squamous epithelia with few mitochondria
Water passively reabsorbed, draws in Na and K
THIN limb

22
Q

What kind of epithelium does the ascending limb of loop of henle have?

A

Cuboidal epithelium with few microvilli but many mitochondria
THICK limb

23
Q

What happens in the ascending limb of the loop of henle?

A

Chloride actively reabsorbed
Sodium passively reabsorbed with it
Bicarbonate reabsorbed
Impermable to water

24
Q

How much water and sodium is reabsorbed by the point of reaching the end of the loop of Henle?

A

85% of water

90% of sodium

25
Q

What is the tubular fluid that leaves the loop of Henle like?

A

Hypo-osmolar with respect to plasma

Because more salt than water has been reabsorbed so the loop is hypo-osmolar with repect to plasma

26
Q

What is the distal convoluted tubule epithelium like? (structure)

A

Cuboidal with few microvilli.
Complex lateral membrane interdigitations with Na+ pumps
Numerous large mitochondria

27
Q

What happens in the distal convoluted tubule?

A

Na+ and Cl- co transporter linked to Ca2+ reabsorption

28
Q

How are Na+ and Cl- reabsorbed in the distal convoluted tubules?

A

By a channel sensitive to thiazides. Thiazides cause a rise in plasma Ca2+

29
Q

What happens at the macula densa of the distal convoluted tubule, what is the macula densa?

A

Part of juxtaglomerular apparatus, detects changes of Na+ conc of filtrate

30
Q

What happens in the distal part of distal covoluted tubule and cortical collecting duct?

A

Fine tuning of the filtrate to maintain homeostasis
DCT - sodium reabsorbed (dependent on aldosterone)
CT - sodium reabsorbed (dependent on aldosterone)
Adjustment of Na/K/H/NH4
Water reabsorbed under control of ADH

31
Q

What is special about distal part of nephron and water?

A

Distal part of nephron impermable to water without ADH

32
Q

What does the principal cell do in the collecting duct and distal part of distal tubule?

A

Important in Na/K/water balance mediated with Na/K ATP pump

33
Q

What does the intercalated cell do in the collecting duct and distal part of distal tubule?

A

Important in acid base balance mediated by H+/ATP pump

34
Q

What is special abou the cortical collecting duct principle cell epithelium

A

Very tight epithelium, very little paracellular transport

35
Q

What are single gene defect conditions that affect tubular function?

A 
Renal tubule acidosis
Bartter syndrome
Fanconi syndrome (dent's disease)
36
Q

What happens in renal tubular acidosis?

A

Hypercholermic metabolic acidosis
Impaired growth
Hypokalemia

37
Q

What happens in Bartter syndrome?

A

Excessive electrolyte secretion
Antenatal Barterr sydrome:
premature birth, polyhydroamnios, severe salt loss, moderate metabolic alkalosis, hypokalemia, renin and aldosterone hypersecretion

38
Q

What happens in Fanconi syndrome?

A

Increased excretion of uric acid, glucose, phosphate and bicarbonate
Increased excretion of low MW proteins
Disease of proximal tubules associated with renal tubular acidosis

Y1 Urinary System (9 decks)

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