6 absorption of ions and water Flashcards

1
Q

What is the difference between villous and crypt enterocytes?

A

villous - absorption

Crypt - secretion

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2
Q

What 3 structures increase the surface area of the small intestine?

A

macroscopic fold of Kerckring
Villi
Microvilli

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3
Q

What are the 2 main routes for water absorption?

A

transcellular

pararcellular

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4
Q

What are the 4 routes of entry for sodium ions?

A

Na/(glucose or amino acid) co-transport
Na-H transporter
parallel Na-H and Cl-bicarbonate exchange
epithelial Na channels

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5
Q

what transporter could be used in Na/glucose co-transport, what else facilitates this movement?

A

SGLT1

Na/K ATPase in basolateral membranes

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6
Q

What facilitates the movement of H ions in the Na-H into the gut lumen?

A

lumen is full of bicarbonate ions

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7
Q

in parallel Na-H exchange, what secondary messenger inhibits Na uptake?

A

cAMP, cGMP, and Ca

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8
Q

In the fasting state, what is significant about parallel Na-H and Cl/HCO3 exchange?

A

it’s electroneutral

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9
Q

What sort of steroid hormone might increase Na absorption?

How?

A

minerlocorticoids, like aldosterone
increase apical Na channel opening
increase Na channel number
increased synthesis of Na channels and Na-k pumps

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10
Q

What are the 3 routes of entry for Chloride ions?

A

passive Cl absorption (channels)
Parallel Na-H and Cl-HCO3 exchange
independent Cl-HCO3 exchange

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11
Q

What is congenital chloridorrhoea, how might it present, and how would you treat it?

A

autosomall recessive, absence of Cl-HCO3 exchanger
dairrhoea, reduced bicarbonate secretion, (alkalyosis)
PPI

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12
Q

Give 4 examples of absorptagogues

A

angiotensin
aldosterone
somatostatin
noradrenaline

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13
Q

What effect will dehydration have on Na absorption?

A

stimulates renin-aldosterone axis, increasing Na absopriton using absorptagogues

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14
Q

Name 2 types of bacterial endotoxins?

A

cholera

E.coli

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15
Q

How does Cholera inhibit Na absorption?

A

cAMP increase, increasing Cl and K secretion and inhibits NaCl absorption

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16
Q

How woul ACh inhibit absorption?

A

Gq, Ca

17
Q

What is Verner Morrison syndrome?

A

pancreatic tumours ultimately cause cAMP increase and hence extensive diarrhoea

18
Q

What is Loperamide?

A

a secretagogue, acting on myenteric plexus in large intestine to decrease motility

19
Q

What are some examples of natural laxatives?

A

bile acids

Ca

20
Q

How can Ca absorption be passive?

A

not under the control of the VDR

21
Q

Where is Ca absorbed?

A

duodenum epithelium

22
Q

What are the 3 steps in Ca absorption?

A

Ca channels
Ca binds to calbindin, acting as a buffer
Ca pump and Na-Ca exchanger on basolateral membrane expel Ca into interstitial fluid