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Nutrition & Metabolism > W3 - Digestive System 2 > Flashcards

W3 - Digestive System 2 Flashcards

1
Q

Where does the majority of digestion take place?

A

Small intestine

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2
Q

What is draped over the small intestine in healthy individuals?

A

Greater omentum

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3
Q

Greater omentum

A

Apron-like fold of visceral peritoneum that hangs down from the stomach.

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4
Q

Characteristics of the Greater omentum

A

Lot of fat for insulation

Rich supply of bv for heat

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5
Q

What 2 anatomical specialisations serve to ⬆️ the SA of the small intestine?

A

Plicae circulares

Villi

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6
Q

Plicae circulares in the small intestine

A

Circular folds in mucosal lining

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7
Q

Villi

A

Extend into lumen of small intestines

Its capillaries enable absorption of nutrients from small intestine –> blood

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8
Q

What do all blood capillaries in the absorptive areas join to form?

A

Hepatic portal venous system

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9
Q

What is a venous portal system?

A

System starting in capillaries

Join to form veins

End in another group of capillaries.

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10
Q

What type of glycosidic bond do maltose + sucrose have?

A

alpha

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11
Q

What type of glycosidic bond does lactose have?

A

Beta

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12
Q

List 3 common sugar alcohols

A

Xylitol

Sorbitol

Mannitol

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13
Q

What are the most common oligosaccharides?

A

Raffinose

Stachyose

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14
Q

What are the 3 main classes of polysaccharides?

A

Starch
Glycogen
Fibres

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15
Q

What are the 2 primary lipolysis enzymes?

A

Lipoprotein lipase (LPL)

Hormone-sensitive lipase (HSL)

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16
Q

What do LPL do with lipoproteins

A

Cleave FAs from chylomicron

= Chylomicron remnant

Cleaves TG from VLDL + IDL

= Forms lipoproteins IDL + LDL (containing less TG)

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17
Q

De novo lipogenesis

A

Synthesis of FAs from ACoA

+

Esterification into TG’s

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18
Q

What ⬆️ activity of HSL?

A

Glucagon

+

Epinephrine

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19
Q

What ⬇️ activity of HSL?

A

Insulin

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20
Q

What does HSL do in hypoglycemia?

A

Cleaves TGs in adipose = FA bound to albumin are released into circulation

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21
Q

Why is HSL important?

A

For mobilising FAs so that they can be used to prod energy

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22
Q

FA oxidation / beta-oxidation occurs in mitochondria but long chain FA can’t diffuse across the mit. membrane.

So how do long chain FAs enter?

A

FA shuttling

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23
Q

What aa-derived compound shuttles long chain FAs into the mitochondria?

A

Carnitine

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24
Q

What are the enzymes involved in FA shuttling?

A

CPTI

CPTII

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25
Q

FA shuttling process

A

FA activated by the addition of a CoA –> ACoA

CPTI adds carnitine –> Acyl-carnitine

^ transported into mit. matrix by translocase enzyme.

In matrix, CPTII removes carnitine from activated FA (acyl-CoA)

Carnitine is recycled back into cytosol to be used again.

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26
Q

What are the 3 major reasons for chewing food?

A

Mechanically ⬇️ size of particles = ⬆️ gastric emptying

⬆️ SA = ⬆️ contact area for digestive enzymes

Mixes food w/ saliva + digestive enzymes.

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27
Q

What is the small intestine divided up into?

A

Duodenum

Jejunum

Ileum

28
Q

What % of absorption takes place in the duodenum + jejunum?

A

~95%

29
Q

What are the folds in the duodenum + jejunum called?

A

Kerckring folds

30
Q

Function of the Kerckring folds

A

⬆️ SA of intestine by ~ 3 times.

31
Q

What does the wall of a villus have?

A

Layer of epithelial cells.

  • Each have a brush border where absorption of nutrients occurs.
32
Q

H20, H20 soluble particles + electrolyte absorption through villi

A

Req. transport or diffusion across luminal + contraluminal membranes of the epithelial cell into bv.

Then transported to liver by hepatic portal vein.

33
Q

What does each villus contain in its central part?

A

Lacteal

34
Q

What does the lacteal in each villus do?

A

Transports particles that arent readily H20-soluble

i.e long-chain FAs via the lymphatic vessels.

35
Q

Depending on its composition, how long does food spend in the GI tract before its eliminated?

A

1-3 days

36
Q

Define transit time

A

Length of time food spends in a section of the GI tract

37
Q

Transit time for small intestine

A

~ 3-10 hrs

38
Q

What does the sphincter of Oddi do?

A

Controls the flow of bile + pancreatic juice into the 2nd part of the duodenum.

39
Q

What does bile consist of?

A

H20

Electrolytes

Bile salts

Cholesterol

Lecithin

Bilirubin

40
Q

Through which duct is bile released?

A

Hepatic duct

41
Q

What does the pancreas secrete to buffer the HCL acid from the stomach?

A

Sodium bicarbonate

42
Q

To what response is pancreatic juice mainly secreted?

A

When there’s chyme in the upper portions of the small intestine.

43
Q

What moves through the ileocecal valve?

A

Chyme

44
Q

Where does chyme move from in the ileocecal valve?

A

Small intestine –> large intestine

45
Q

What is contraction of the ileocecal valve regulated by?

A

Distension of the cecum

Irritating substances in the cecum

Fluidity of chyme

46
Q

What can restrict the emptying of the ileum?

A

An inflamed appendix

47
Q

What does increased fluidity of the chyme increase?

A

Emptying from the ileum

48
Q

What does parasympathetic stimulation do to the GI tract?

A

Stimulates motility

49
Q

What is the source of the parasympathetic activity in the oesophagus, stomach, pancreas, gall bladder, small intestine + upper section of the large intestine?

A

Vagus nerve

50
Q

Where does the lower portion of the large intestine receive parasympathetic innervation from?

A

Spinal nerves in sacral region

51
Q

What does gastrin do?

A

⬆️ HCL acid + pepsinogen secretion in stomach

52
Q

What does secretin do?

A

⬆️ H20 + bicarbonate secretion by pancreas.

53
Q

How long can it take for digestion to be completed?

A

~ 4-6 hrs

54
Q

What does saliva consist of?

A

99.5% H20

a-amylase

Mucoid proteins

Bicarbonate

Electrolytes

Lysosomes

Lingual lipase

Protein antibodies.

55
Q

What do the mucoid proteins do to saliva?

A

⬆️ its viscosity

= Helps lubricate food = easier to swallow.

56
Q

Where is guanylin secreted?

A

Ileum + colon

57
Q

What does guanylin do?

A

Removes NaCl + H20 from faeces.

58
Q

When is the hydrolysis of all starches to maltose almost complete?

A

When chyme enters ileum.

59
Q

What do the lingual + gastric lipase act together MAINLY on?

A

Short chain (C4-C6)

Medium chain (C8-C10)

TAG

Whereas most of the long-chain (C12-C14) are digested in the small intestine.

60
Q

What % is lingual lipase responsible for of triacylgylcerol digestion?

A

10-30%

61
Q

Functions of HCL acid

A

Activates protease enzyme pepsin

Kills pathogenic organisms

⬆️ Absorption of iron + calcium

Breaks down food proteins = ⬆️ vulnerability to enzymes

62
Q

Where are proteases often stored?

A

In inactive precursors

But as soon as released into stomach or small intestine, they’re activated.

63
Q

Where does most vitamin absorption take place?

A

Jejunum

Ileum

  • Usually by diffusion
64
Q

Upper GI symptoms often reported by athletes

A

Heartburn

Bloating

Vomiting

65
Q

Lower GI symptoms often reported by athletes

A

Urge to defecate

Loose stool

Diarrhoea

Bleeding

Nutrition & Metabolism (17 decks)

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