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REB > 22. Renal Tubular Function and Physiology > Flashcards

22. Renal Tubular Function and Physiology Flashcards

1
Q

What is tubular reabsorption?

A

Solutes and water are removed from tubular fluid and transported into the blood

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2
Q

What is the function of tubular reabsorption?

A

Maintains homeostasis of blood volume, pressure, pH and osmolarity

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3
Q

What is tubular secretion?

A

Transport of solutes from interstitium into tubular lumen

Clears substrates from blood

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4
Q

Name 5 things secreted into filtrate

A 
K+
H+
NH4+
Creatinine
Urea
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5
Q

What type of epithelium is found in the PCT and thick limb of loop of henle?

A

Cuboidal

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6
Q

What are important features of the tubular cells in the PCT?

A

Microvilli to increase surface area for absorption

Mitochondria for active reabsorption

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7
Q

What type of epithelium is found in the thin limb of loop of henle?

A

Squamous

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8
Q

What are tight junctions?

A

Contact between neighbouring cells on the luminal surface

Transmembrane proteins form bonds with their same type on the other cell

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9
Q

What proteins are found in tight junctions?

A

Occludins
Claudins
Junctional Adhesion Molecule

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10
Q

What is functional polarity?

A

Epithelial cells express different transport proteins on their apical and basolateral sides
Allows for directional transport of solutes

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11
Q

Which aquaporin is found in the PCT and DLoH?

A

1

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12
Q

Which aquaporins are found in the DCT and CD?

A

2,3,4

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13
Q

How is Na reabsorbed in the early PCT?

A

Na/K pump maintains electrochemical gradient for Na+ absorption across apical membrane
Na+ exchanged with H+ to re-enter cell
HCO3- reabsorbed with Na+

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14
Q

How is Cl reabsorbed in the late PCT?

A

Cl- builds up in filtrate
Late PCT is permeable to Cl-
Reabsorbed passively through paracellular pathway

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15
Q

How is glucose reabsorbed in the early PCT?

A

Dependent on energy of Na/K
Enters through Na+/glucose co-transporter (SGLT-2)
Exits cell via GLUT 2

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16
Q

Name a gliflozin

A

Dapaglifozin

17
Q

How do gliflozins work?

A

Target SGLT2
Increases amount of glucose excreted
Lowers blood glucose in diabetics

18
Q

How is protein reabsorbed in the PCT?

A

Receptor mediated endocytosis
Proteins are degraded in intracellular lysosomes
AAs exit via basolateral transporters

19
Q

What does glycosuria with normoglycaemia indicate?

A

Decreased tubular resorptive capacity

20
Q

What are 2 reasons for glycosuria with normoglycaemia?

A

Pregnancy

Falconi syndrome

21
Q

What are the 3 types of proteinuria?

A

Glomerular (damage causes more protein to be filtered)
Tubular (alterations in reabsorption)
Overload (increase plasma low weight proteins)

22
Q

How are AAs reabsorbed in the PCT?

A

Na+ coupled secondary active transport
Small amounts of passive reabsorption
Separate carriers on apical and basolateral membranes for different types of AAs

23
Q

How is HCO3- reabsorbed in the PCT?

A

Filtered HCO3- can’t cross the apical membrane due to its charge
Combines with H+ to produce carbonic acid, breaks down into CO2 and water
CO2 crosses membrane, recombines with water to produce HCO3-
HCO3- crosses basolateral membrane via a Na+/HCO3- symporter

24
Q

How are organic ions secreted in the PCT?

A

Through multiple different transporters

Multiple Drug Resistance Protein, p-glycoprotein, Organic Acid Transporters, Organic Cation Transporters

25
Q

What is the osmolarity when entering and leaving the loop of Henle?

A

Entering: 300mOsm/L
Leaving: 100mOsm/L

26
Q

What is the highest osmolarity in the medulla?

A

1200mOsm/L

27
Q

Name 2 loop diuretics

A

Bumetanide

Furosemide

28
Q

How do loop diuretics work?

A

Inhibit NKCC2 in the thick ascending limb which stops salt reabsorption

29
Q

Who are loop diuretics effective for?

A

Patients with renal insufficiency or severe oedema

30
Q

How is NaCl reabsorbed in the early DCT?

A

Na+ enters via apical Na/Cl contransporters

Cl- leaves via basolateral channels

31
Q

What inhibits NaCl reabsorption in the early DCT?

A

Thiazide diuretics

32
Q

How is Ca++ reabsorbed in the DCT?

A

Active transcellular transport

Regulated by parathyroid hormone

33
Q

What are principal cells in the late DCT and CD involved in?

A

NaCl transport

34
Q

How is NaCl transported by principal cells?

A

Na+ reabsorbed through NCC and ENaC
Na+ reabsorption creates a negative charge in the lumen
K+ moves out

35
Q

What controls ENaC channels?

A

Aldosterone

36
Q

How do K+ sparing diuretics work?

A

Inhibiting ENaC or aldosterone in late DCT/CD

37
Q

What does ADH regulate?

A

Aquaporins

Urea reabsorption

38
Q

What is the function of intercalated cells?

A

Control acid/base balance

39
Q

How do intercalated cells excrete acid?

A

Excreted across apical membrane by H+ ATPase or H/K ATPase

REB (29 decks)

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