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GASTRO-INTESTINAL MEDICINE AND HEPATOLOGY > INTEGRATED FUNCTION OF THE GUT > Flashcards

INTEGRATED FUNCTION OF THE GUT Flashcards

1
Q

What are the two plexi found within the wall of the GI tract?

A

Myenteric plexus

Submucosal plexus

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2
Q

Where is the myenteric plexus found in the wall of the GI tract?

A

Between the longitudinal and the circular layers of the muscle.

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3
Q

What is another name for the myenteric plexus?

A

Auerbach’s plexus

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4
Q

What is another name for the submucosal plexus?

A

Meissner’s plexus

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5
Q

What is the main function of the myenteric plexus?

A

Coordinates gut movement

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6
Q

What is the main function of the submucosal plexus?

A

Control glands

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7
Q

What is another name for the mixing process that occurs in the large intestine?

A

Haustral contractions

Segmental contractions

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8
Q

What causes haustral contractions?

A

Contraction of the taeniae coli

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9
Q

What is the gastrocolic reflex?

A

Food leaving the stomach to reach the duodenum sets of a reflex which sends a massive intense contraction through the transverse colon and pushes contents into rectum.

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10
Q

What is the role of the pacemaker cells in the stomach?

A

Set the basic electrical rhythm for contractions - about 3 per minute

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11
Q

How does the mixing of food happen within the stomach?

A

Contractions push the food down the stomach, however, because the pyloric sphincter is closed, the smaller bits get pushed back up into the body of the stomach, while the bigger bits get squashed and broken up.

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12
Q

What do the force and frequency of contractions in the stomach depend on?

A

Intrinsic neural activity
Myogenic properties of smooth muscle
Hormones being secreted

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13
Q

Which type of food will empty from the stomach first? Carbohydrate, Fat, Protein

A

Carbohydrate

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14
Q

Which type of food will take the longest to empty from the stomach? Carbohydrate, Fat, Protein

A

Fat

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15
Q

What affect do fatty acids have on the pyloric sphincter?

A

Increases contractility

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16
Q

How does osmotic pressure of the contents of the duodenum affect rate of gastric emptying?

A

Hyperosmotic (very concentrated) chyme activates osmoreceptors in the duodenum that decrease gastric emptying.

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17
Q

What nerves is responsible for allowing the stomach to distend?

A

Vagus

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18
Q

Where in the GI tract is the Auerbach plexus not between the circular and longitudinal muscle? Where is it found?

A

In stomach

Between the oblique and the circular layers.

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19
Q

Which hormones are released by the duodenum in response to the presence of chyme coming through the pyloric sphincter? What is their function?

A

Somatostatin
Secretin
Cholecystokinin
Gastric intestinal peptide

All inhibit gastric empyting

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20
Q

Is the small intestine doing anything in the fasting state?

A

Yes. There are migrating motor complexes that occur every 90-120 mins.

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21
Q

What is the role of the migrating motor complexes that occur in the small intestine during the fasting state?

A

Move indigestible food such as tomato skins, nuts and sweetcorn

Remove dead epithelial cells

Prevent bacterial overgrowth

Stop colonic bacteria entering the small intestine.

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22
Q

What is the medical term for vomiting?

A

Emesis

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23
Q

What are the associated symptoms to vomiting?

A 
Tachycardia
Sweating
Nausea
Pallor
Salivation
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24
Q

How does the body make sure that vomit does not make its way into the nasopharynx?

A

The soft palate rises to block entry into it

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25
Q

What are the different classes of drug that increase GI tract motility?

A 
Fecal softeners
Bulk laxatives
Osmotic laxatives
Stimulant laxatives
Motility stimulants
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26
Q

Name 2 types of osmotic laxatives and describe how they work.

A

Lactulose - disaccharide of fructose and galactose which is degraded by bacteria. Monosaccarides ferment to produce lactate and acetate which draw water into intestine.

Saline purgatives - such as magnesium sulphate and magnesium hydroxide. Increases tonicity hence drawing more water into the lumen.

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27
Q

What are the different classes of drug that decrease GI tract motility?

A

Anti-diarrhoeal drugs

Antipasmodics

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28
Q

How do the anti-pasmodic drugs work? (They decrease gut motility)

A

2 types:

Anti-muscarinics - decrease muscle tone by inhibiting parasympathetic activity

Mebeverine - acts directly on smooth muscle

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29
Q

What is the role of somatostatin?

A

Inhibits most secreting cells of the GI tract and pancreas.

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30
Q

What is the role of cholecystokinin?

A

Inhibits gastrin production from the stomach and hence slows emptying

Stimulates gallbladder contraction

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31
Q

What is the role of leptin?

A

Signals satiety to the central nervous system

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32
Q

What is the role of ghrelin?

A

Signals hunger to the central nervous system?

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33
Q

What stimulates the release of secretin?

A

Acid in the duodenum

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34
Q

What is the role of secretin?

A

Reduces stomach motility
Inhibits acid production
Stimulates pancreas to release enzyme

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35
Q

What is the role of vasoactive intestinal peptide?

A

Increases secretion of fluid and chloride into the lumen by the wall of the GI tract

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36
Q

What is the role of glucagon?

A

Counteracts insulin by increasing sugar levels in the blood by stimulating glycogenolysis and gluconeogenesis.

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37
Q

Where is glucagon released from?

A

Alpha cells of the pancreas

38
Q

What stimulates the release of enteroglucagon?

A

Food in the lumen

39
Q

What is the role of enteroglucagon?

A

Proliferation of cells in the small intestine

40
Q

Where is gastrin release from?

A

G cells in the stomach.

41
Q

What is the role of gastrin?

A

Increased HCl production

42
Q

What stimulates cholecystokinin release?

A

Free fatty acids in the small intestine

43
Q

What is the role of peptide YY?

A

Slows peristalsis in the large intestine.

44
Q

What is the role of motilin?

A

Stimulates migrating motor complex during fasting

45
Q

Which is more precise sensation? Visceral or somatic?

46
Q

Where is pain from appendicitis initially felt?

A

Peri-umbilical pain

47
Q

Why does the pain from appendicitis spread or progress?

A

inflammation initially only affects the inner layers of the appendix, which have only visceral nerve supply. However, as the inflammation spreads the parietal and visceral peritoneum become involved and the somatic nerves to the peritoneum are stimulated. Pain is now localized to the right iliac fossa.

48
Q

Which part of the small intestine is very specialized for the absorption of folic acid?

49
Q

Where do the capillaries from the small intestine eventually drain into?

A

Hepatic portal vein

50
Q

What are lacteals (found in the small intestine)?

A

They are lymphatic capillaries that absorb dietary fats and pass them through the lymphatic system.

51
Q

How are the fat soluble products of digestion carried in the lacteals?

A

In protein bound bundles called chylomicrons. (Lipoproteins)

52
Q

What is the main component of mucus in the small intestine which prevents self-digestion?

53
Q

Why do some cancer drugs affects the small bowel so much?

A

Because there is relatively rapid turnover of the cells. Average life of mucosal epithelial cell is 48 hours.

54
Q

What are the monomers that make up sucrose?

A

Glucose and fructose

55
Q

Where are the enzymes that breakdown polysaccharides and disaccharides of carbohydrates secreted from?

A

The villi of the wall of the small intestine

56
Q

How is glucose taken up from the lumen of the small intestine?

A

Taken up by sodium/glucose cotransporter.

57
Q

How is galactose taken up from the lumen of the small intestine?

A

Competes with glucose for the same sodium/glucose cotransporter.

58
Q

In what form are most of the dietary fats the we ingest?

A

Triglycerides

59
Q

What percentage of our energy intake do triglycerides make up?

60
Q

What is the difference between a saturated and a non-saturated fatty acid?

A

Presence or lack of double bonds

61
Q

Other than, triglycerides what other forms of dietary fat are there?

A

Phospholipids

Cholesterol and steroids

62
Q

Which bond do lipases cleave in a triglyceride?

A

Two of the bonds between the glycerol molecule and the fatty acid. This leaves a monoacylglycerol molecule.

63
Q

What enzyme(s) cleave(s) the final bond between the glycerol molecule and the fatty acid in the monoacylglycerol molecule?

A

Pancreatic esterases

Intracellular lipases

64
Q

Which hormone is responsible for the contraction of the gall bladder and hence the secretion of bile?

A

Cholecystokinin

65
Q

What is the role of bile?

A

Emulsifies fats and package them into small micelles

66
Q

How are primary bile salts broken down?

A

By bacteria in the large bowel

67
Q

What do amino-peptidases do?

A

Breakdown of proteins from the amino end.

68
Q

What do endopeptidases do?

A

Breakdown of proteins from the middle.

69
Q

What do carboxypeptidases do?

A

Breakdown of proteins from the carboxy end.

70
Q

Where are dipeptidases and tripeptidases found?

A

In the brush border.

71
Q

Is there are single type of amino acid transporter?

A

No. There are different sodium dependent transporters which are all side chain specific.

72
Q

What is phytic acid (phytate) and why can it be a problem in the diet of some people?

A

It is found in unleavened wheat diets. It can bind to certain minerals such as iron and zinc and prevent them from being absorbed.

73
Q

What is the role of vitamin C in the absorption of iron?

A

Reduces iron from Fe3+ to Fe2+

74
Q

What is the vitamin required to absorb calcium from the gut?

75
Q

How is vitamin B12 taken up in the small intestine?

A

Bound to intrinsic factory by receptor-mediated endocytosis

76
Q

What is the action of trehalase and where is it found?

A

Converts trehalose into glucose at the brush border in the small intestine.

77
Q

What are the four components of chylomicrons?

A

Triglycerides (85-92%)
Phospholipids
Cholesterol
Protein

78
Q

What are the two pathways by which information from the GI tract can regulate hunger and satiety?

A

Gut hormones

Vagal afferent nerves

79
Q

What are the two hormones involved in long term signals of how much body stores of energy we have?

A

Leptin

Insulin

80
Q

Where does leptin come from?

A

Adipose tissue

81
Q

Where are the leptin receptors found in the brain?

A

Hypothalamus

82
Q

How does the digestion of food lead to the feeling of satiety via that the vagus nerve?

A

Amino acids and monosaccharides are detected by receptors in the gut lining. These cells release paracrine hormones that are detected by nerve ending of the vagus nerve, which in turn transmits information to the hypothalamus.

83
Q

What stimulates the release of cholecystokinin?

A

Fat and protein in the duodenum.

84
Q

What are the roles of cholecystokinin?

A

Stimulants gall bladder to secrete bile.

Stimulate vagal nerve endings to transmit presence of meal to hypothalamus.

85
Q

Where is polypeptide Y secreted from?

86
Q

What is the role of polypeptide Y?

A

Signal satiety.

Decreases ileal motility to allow full absorption of nutrients.

87
Q

What is the role of Glucagon-like peptide-1?

A

Decreases GI motility

Causes insulin release (its an incretin)

88
Q

Where is ghrelin released from?

A

Fundus of the stomach

89
Q

What is the role of ghrelin?

A

Triggers appetite in the absence of food

90
Q

Which patients might you give glucagon-like peptide-1 (GLP-1) agonists to?

91
Q

What is the role of dipeptidyl peptidase 4 (DPP-4)?

A

The enzyme that breaks down glucagon-like peptide-1 (GLP-1). It is a therapeutic target for diabetics.

92
Q

Give an example of a dipeptidyl peptidase 4 (DPP-4) inhibitor which might be used to treat a diabetic?

A

Sitagliptin
Gemigliptin
(All end in liptin)

GASTRO-INTESTINAL MEDICINE AND HEPATOLOGY (24 decks)

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