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HUBS192 > lecture 27 > Flashcards

lecture 27 Flashcards

1
Q

What is absorption?

A

the net passage of substances from the GI lumen across the lining of the intestine into the interstitial fluid or lymph

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2
Q

Where is the primary site of absorption?

A

Small intestine

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3
Q

Sites of absorption?

A

Mouth, oesophagus, stomach

Small and large intestine

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4
Q

What is absorbed at mouth, oesophagus and stomach?

A

lipid soluble substances

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5
Q

What is absorbs at small intestine?

A

90% of water and sodium, all nutrients

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6
Q

what is absorbed at large intestine?

A

9% of water and sodium

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7
Q

factors effecting absorption?

A

Motility
surface area
transport across epithelium
removal of interstitial fluid

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8
Q

what does correct rate of propulsion allow?

A

digestion and absorption

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9
Q

what exposes products of digestion to absorptive surfaces?

A

motility and segmentation

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10
Q

rate of absorption is proportional to?

A

surface area

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11
Q

what anatomic adaptions maximise surface area?

A

length of intestine
circular folds
villi
microvilli

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12
Q

what acts as a barrier between outside world and bloodstream?

A

intestinal epithelium

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13
Q

why is there so many microbiomes in GI tract?

A

the lumen of the intestine is continuous with the outside world

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14
Q

What are the two pathways of transport of molecules across epithelium?

A

paracellular gaps

cellular

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15
Q

what is the non-selective barrier that binds cells together?

A

tight junction

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16
Q

what is required for cells to do paracellular travel?

A

a concentration gradient

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17
Q

how many membranes do the solutes have to pass to reach blood or lymph?

A

two membranes, apical and basal

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18
Q

what reduces nutrients into their smallest possible units?

A

chemical digestion

19
Q

benefits of transport proteins?

A

Absorb what is required

allows active transport

20
Q

why is there a large blood flow to intestine?

A

for removal of substance from interstitial fluid

21
Q

villi are arranged around?

A

blood vessels and lacteals?

22
Q

how do you lose water?

A

Sweat, urine, faeces, breath

23
Q

what is the total water delivered to small intestine?

A

~9-10L per day

24
Q

What is the mechanism of water absorption?

A

osmosis

25
Q

what is osmosis?

A

passive movement of water from lumen into the blood

26
Q

How is sodium absorbed?

A

Passive movement via paracellular pathway

active transport via cells

27
Q

mechanisms of sodium absorption?

A

Na+ channels
Na+ transport coupled to monosaccharides
Na+ transport coupled to amino acids

28
Q

Going from lumen into epithelial cells Na+?

A

moves down the concentration gradient through channels and Na+/H+ transporters

29
Q

To move from epithelial cells to interstitial fluid, Na+ requires?

A

active transport to move up the gradient

30
Q

2 mechanisms for carbohydrate absorption?

A

Passive or active

31
Q

Passive absorption of carbohydrates is?

A

monosaccharides diffusing down concentration gradient via paracellular pathway

32
Q

Active absorption of carbohydrates requires co-transport with?

A

Na+ via cellular pathway

33
Q

how are di and tri - peptides transported?

A

via H+ dependent cotransport

34
Q

how are amino acids transported?

A

via Na+ dependent cotransport

35
Q

Do products of fat digestion require a transporter?

A

No, they are lipid soluble and diffuse freely

36
Q

How are products of fat digestion delivered to brush border?

A

micelles

37
Q

What happens to products of fat digestion when it enters the cell?

A

resynthesised into triglycerides, packaged into chylomicrons which exit via exocytosis and enter lacteals

38
Q

in the ileum how are bile salts absorbed?

A

active transport processes

apical Na+ dependent bile acid cotransporter

39
Q

How is bile salts absorbed in the colon?

A

passive absorption

40
Q

when does bile salt absorption occur?

A

after fat absorption is complete

41
Q

What are fat soluble vitamins?

A

A, D, E, K

42
Q

when are fat soluble vitamins absorbed?

A

Absorbed with fats

43
Q

What is a water soluble vitamin and how are they absorbed?

A

Na+ dependent absorption

vitamin c

44
Q

How is vitamin B12 absorbed?

A

Absorbed in the ileum bound to intrinsic factor

HUBS192 (38 decks)

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