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HUBS 192 > Lecture 27: Absorption > Flashcards

Lecture 27: Absorption Flashcards

1
Q

What is absorption?

A

The passage of substances from the GI lumen across the lining of the intestine into the interstitial fluid and then into the blood or lymph

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2
Q

What are the sties of absorption?

5

A
  • Mouth
  • Oesophagus
  • Stomach
  • Small intestine
  • Large intestine
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3
Q

What does the correct rate of propulsion allow?

2

A
  • Digestion

- Absorption

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4
Q

What does the correct rate of motility ensure?

A

Exposure of products of digestion to absorptive surface

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5
Q

What is rate of absorption proportional to?

A

Surface area

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6
Q

What happens when the surface area of absorption is greater?

A

The rate of absorption increases

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7
Q

What are anatomical adaptations that maximise surface area?

4

A
  • Length of intestine
  • Circular folds
  • Villi
  • Microvilli
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8
Q

What is the lumen of the intestine continuous with?

A

The outside world

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9
Q

What is a barrier between the underlying components of the intestinal lumen and the environment?

A

The intestinal epithelium

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10
Q

What are the 2 pathways across the epithelium barrier?

A
  • Paracellular

- Transcellular

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11
Q

What is the paracellular pathway across the epithelium?

A

A gap between the cells

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12
Q

What is the cellular pathway across the epithelium?

A

Across the cell membranes through the cytoplasm

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13
Q

What do solutes not do?

A

Cross cell membranes

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14
Q

What is the only barrier for solutes using paracellular pathways?

A

Tight junctions binding cells together

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15
Q

Paracellular pathways are relatively what?

A

Non-selective

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16
Q

If a solute is relatively what? it can get across a paracellular pathway

A

Small

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17
Q

What does movement through a paracellular pathway require?

A

A concentration gradient

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18
Q

Using a cellular pathway what must solutes cross?

A

Two cell membranes

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19
Q

What are cell membranes?

A

Lipid bilayers

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20
Q

If a solute is not lipid soluble what does it require for the cellular pathway?

A

A transport protein

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21
Q

To maximise the absorption across available surface area nutrients are reduced to what?

A

Their smallest possible unit

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22
Q

What do specific transport proteins do?

A

Absorb what is required

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23
Q

What do specific transport proteins allow?

A

Active transport against a concentration gradient

24
Q

What is there a large blood flow to?

A

The intestine

25
Q

What do the arrangement of blood vessels and lacteal in villi prevent?

A

The build up in interstitial fluid

26
Q

What is the mechanism of water absorption?

A

Osmosis

27
Q

What is osmosis?

A

Passive movement of water from lumen into blood

28
Q

How is the osmotic gradient set up?

A

By the absorption of salts and nutrients

29
Q

How is sodium absorbed?

2

A
  • Passive movement via paracellular pathways

- Active transport via cells

30
Q

Active transport of sodium across cell membranes can use what mechanisms?
(3)

A
  • sodium transport alone
  • sodium transport coupled to monosaccharides
  • sodium transport coupled to amino acids
31
Q

When moving alone what does sodium move down?

A

Its concentration gradient

32
Q

When moving alone what does sodium move through?

A

Transport proteins

33
Q

When moving out of a cell what does sodium need to move from and to?

A

From a low concentration to a high concentration

34
Q

What does sodium use to move out of a cell?

A

ATP

35
Q

How are carbohydrates absorbed?

A

Active absorption/Cotransport with sodium via cellular pathway

36
Q

What are carbohydrates absorbed as?

A

Monosaccharides

37
Q

How are proteins absorbed?

A

By passive or active absorption

38
Q

When moving passively what do amino acids move down?

A

Concentration gradient via paracellular pathways

39
Q

What are Di- and tri- peptides absorbed via?

A

via H+ dependant cotransport

40
Q

What are amino acids absorbed via?

A

Via sodium dependent cotransport

41
Q

Are products of fat digestion lipid-soluble?

A

Yes

42
Q

What can lipid soluble products diffuse across?

A

The cell membrane

43
Q

How are lipid soluble products delivered to the brush border?

A

Micelles

44
Q

In the cell what are products of fat resynthesised into?

A

Triglyerides

45
Q

What do products of fats in the cell get packaged into?

A

Chylomicrons

46
Q

What do chylomicrons exit the cell by?

A

Exocytosis

47
Q

What do chylomicrons enter?

A

The lacteals

48
Q

what happens to bile salts in micelles?

A

They are eventually absorbed

49
Q

Where are bile salts from micelles absorbed?

A

Ileum

50
Q

When are bile salts from micelles absorbed?

A

After fat absorption is complete

51
Q

How are bile salts absorbed in the colon?

A

by passive absorption

52
Q

What are the 2 classes of vitamin?

A
  • Fat soluble

- Water soluble

53
Q

What are 4 fat soluble vitamins?

A

vitamin A, D, E, K

54
Q

What are fat soluble vitamin absorbed with?

A

Fats

55
Q

What are water soluble vitamins?

2

A
  • Sodium

- Vitamin C

56
Q

Where are faeces formed?

A

Large intestine

HUBS 192 (38 decks)

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