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Gastro-intestinal System > The Intestines And Inflammatory Bowel Disease > Flashcards

The Intestines And Inflammatory Bowel Disease Flashcards

1
Q

What are the main roles of the intestines?

A

Absorb nutrients
Water
Electrolytes

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2
Q

What are the basic cells of the intestine?

A

Enterocytes

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3
Q

What are plicae circulares?

A

Valvular flaps projecting into the lumen of the small intestine

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4
Q

Why is mucus in the gut important?

A

Keeps the bacteria away from the cells

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5
Q

How often is mucosa shed in the gut?

A

3-6 days

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6
Q

Describe the cells in intestinal glands

A

Stem cells at the base - migrate to surface as they mature
Enteroendocrine - release hormones
Paneth cells - protection against infection

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7
Q

What types of carbohydrates can be absorbed?

A

Monosaccharides

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8
Q

Where does the final breakdown of carbohydrates occur?

A

In the brush border of the gut

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9
Q

What are the monosaccharides?

A

Fructose
Galactose
Glucose

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10
Q

What are the common dietary carbohydrates?

A

Starch
Lactose
Sucrose

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11
Q

What are the 2 parts of starch?

A

Amylose (20%)

Amylopectin (80%)

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12
Q

What type of bonds make the straight chains in starch?

A

Alpha 1, 4 glycosidic

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13
Q

What type of bonds make the branching chains in starch?

A

Alpha 1, 6 glycosidic

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14
Q

Which bonds does amylase break?

A

Alpha 1, 4 glycosidic

Usually cleaves at the ends of straight chains

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15
Q

What are alpha dextrins?

A

Smaller units from starch that still contain branches

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16
Q

Which enzyme breaks alpha 1,6 glycosidic bonds?

A

Isomaltase

This enzyme has many different names

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17
Q

Which enzymes are found in the brush border?

A

Maltase
Isomaltase
Lactase
Sucrase

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18
Q

Describe SGLT-1

A

Sodium glucose transporter
Na/K/ATPase sets up the gradient
On apical membrane
Cotransports glucose or galactose with Na+ into enterocyte

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19
Q

Describe GLUT-5

A

On the apical membrane

Transports fructose into the enterocytes

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20
Q

Describe GLUT-2

A

Basolateral membrane
All the monosaccharides pass through this into the blood
Down their concentration gradients

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21
Q

Describe the idea behind oral rehydration methods

A

Uptake of Na+ generates osmotic gradient so water follows
Glucose uptake stimulates Na+ uptake
A mixture of glucose and salt will stimulate maximum water uptake

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22
Q

What kinds of peptides can be absorbed in the gut?

A

Amino acids
Dipeptides
Tripeptides

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23
Q

Describe the first part of protein digestion

A

In the stomach, acid unravels proteins
Pepsinogen secreted from chief cells
Converted to pepsin by HCl
Pepsin breaks down proteins

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24
Q

Trypsinogen is converted to trypsin by …

A

Enteropeptidase (on brush border)

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25
Q

Which pancreatic protease activates all the other proteases?

A

Trypsin

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26
Q

How do exopeptidases work?

A

Break bonds at ends of polypeptides

Produces dipeptides/amino acids

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27
Q

How do endopeptidases work?

A

Break bonds in middle of polypeptides

Produce shorter polypeptides

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28
Q

Name an exopeptidase

A

Carboxypeptidase

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29
Q

Name 3 endopeptidases

A

Trypsin
Chymotrypsin
Elastase

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30
Q

Why can newborns absorb whole proteins?

A

Needed to help immunity etc when breast feeding

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31
Q

How are amino acids transported into cells?

A

Na+ amino acid transporter

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32
Q

How are most protein products absorbed?

A

As dipeptides or tripeptides
Via H+ co-transporter
(PepT 1)
Inside the cells, further broken down into amino acids

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33
Q

Which hormone induces the Na+ channels in the large intestine?

A

Aldosterone

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34
Q

What is the difference in absorption when calcium is normal/high and when it is low?

A 
Normal/high = calcium absorbed passively paracellular 
Low = active transcellular absorption (facilitated diffusion apical and pumped out of basolateral by Ca-ATPase)
35
Q

How is iron absorbed?

A

Haem/Fe2+

Cotransported with H+ (why gastric acid is important to this)

36
Q

What happens to iron when iron levels are low?

A

Binds to transferrin

Transported to stores

37
Q

What happens to iron when levels are high?

A

Contained in ferritin complexes
Trapped inside enterocyte
Can be transported out if we need it
Lost when enterocyte is shed

38
Q

How is iron stored in the body?

A

Approx 1/2 is in Hb

Approx 1/2 stored in ferritin complexes in bone marrow, liver and spleen

39
Q

How are water soluble vitamins absorbed?

A

Via Na+ cotransport

40
Q

How is vitamin B12 absorbed?

A

In the terminal ileum

Bound to intrinsic factor (secreted by parietal cells)

41
Q

B12 deficiency leads to …

A

Megaloblastic anaemia

42
Q

How does the small intestine ensure caudal drive of contents?

A

Intestinal pacemakers have higher frequencies proximally
Intestinal gradient set up
Drives the contents caudally
Peristaltic contractions

43
Q

What is segmentation?

A

Contents move back and forth on a particular area
Shuttling to increase the contact time
Aid absorption

44
Q

What is mass movement?

A

Occurs 1-3 times a day
Contents move rapidly from transverse colon to rectum
Often triggered by eating (gastro-colic reflex)

45
Q

What are haustra?

A

In the large intestine
Formed because the longitudinal muscle (taenia coli) is not the complete length
Forms pouches

46
Q

When do we get the urge to defaecate?

A

Stretch receptors activated

When rectum is 25% full

47
Q

Describe the internal and external anal sphincters

A

Internal - smooth muscle, PNS control

External - striated/skeletal muscle, voluntary control

48
Q

How do we defaecate?

A

Relax both the internal and external anal sphincters

Increase intra-abdominal pressure

49
Q

What are inflammatory bowel diseases?

A

A group of conditions characterised by idiopathic inflammation of the GI tract (affecting the function of the gut)

50
Q

What are the 2 most common IBDs?

A

Crohn’s disease

Ulcerative colitis

51
Q

What are the peak ages for Crohn’s disease?

A

15-30 years

60 years

52
Q

What is the peak age for UC?

A

Young adults

53
Q

What is diversion colitis?

A

Inflammation distal to a surgical cut through the bowel

54
Q

What is microscopic colitis?

A

Can only see the inflammatory changes on histology

55
Q

Where does Crohn’s affect?

A

Anywhere in the GI tract

Ileum involved in most cases

56
Q

Which IBD is more likely to be transmural?

A

Crohn’s

Through all layers of bowel wall

57
Q

Which IBD presents with skip lesions?

A

Crohn’s

58
Q

Where does UC commonly affect?

A

Begins in rectum

Can extend to involve entire colon

59
Q

Which IBD is found in a continuous pattern?

A

UC

60
Q

Which IBD usually just has mucosal (superifical) inflammation?

A

UC

61
Q

Name some extra-intestinal problems linked to IBDs

A

MSK pain - arthritis
Erythemanodosum, pyoderma gangrenosum, psoriasis
Primary sclerosing cholangitis
Eye problems

62
Q

What things can trigger the start of an IBD?

A

Antibiotics
Infections
Smoking
Diet

63
Q

Describe Crohn’s and the affect on the body

A

Inflammation in area that would normally absorb nutrients
More water left in the gut lumen - diarrhoea
Weight loss due to not absorbing enough
Terminal ileum involvement - vita B12 deficiency - megaloblastic anaemia
Hyperaemia
Mucosal oedema

64
Q

Which IBD is more likely to present with strictures?

A

Crohn’s

65
Q

Which IBD can give a cobblestone appearance?

A

Crohn’s

66
Q

What is a cobblestone appearance?

A

Areas of oedema surrounded by ulceration

67
Q

Where can the bowel form fistulae to?

A

Other parts of bowel
Bladder
Vagina
Skin

68
Q

What microscopic evidence signifies Crohn’s disease?

A

Granulomata

69
Q

How would we investigate for Crohn’s disease?

A

Bloods - anaemia
CT/MRI - bowel wall thickness, obstruction, extramural problems
Barium enema (less likely) and xray
Colonoscopy - biopsy - histology

70
Q

Is UC more common in males or females?

A

Females

71
Q

Describe some general features of UC

A

Pain tends to be less localised than Crohn’s
Always in rectum
Inflammatory infiltrate of lamina propria
Crypt abscesses and distortion
Decreased goblet cells - less mucus so loss of protection
Loss of haustra

72
Q

Which IBD is more likely to have crypt distortion?

A

UC

73
Q

Which IBD has a decreased production of mucus?

A

UC

74
Q

Describe the investigations for UC

A 
Bloods - anaemia, serum markers
Stool cultures
Plain abdominal x-ray 
CT/MRI 
Colonoscopy
Barium enema
75
Q

What do we call cases that cannot be classed as either Crohn’s or UC?

A

Indeterminate colitis

76
Q

In which IBD is bleeding more common?

A

UC

77
Q

Which IBD is more likely to present with perianal disease?

A

Crohn’s

78
Q

In which IBD is fibrosis more common?

A

Crohn’s

79
Q

In which IBD is the mucosa friable? (Delicate)

A

UC

80
Q

What would you see using radiology for Crohn’s?

A

Lots of narrowing in the lumen of gut
Lots of distortion due to inflammation and healing
‘String sign of Cantour’

81
Q

What would you see in the radiology for UC?

A

Lead pipe colon (featureless bowel - no haustra)

Contrast medium may adhere to walls of bowel - see the continuous ulceration

82
Q

What are the treatment options for IBDs?

A

Stepwise

  1. Aminosalicylates for flares and remission
  2. Corticosteroids for flares only (avoid long term)
  3. Immunomodulators for extreme cases, fistulae and maintenance of remission
  4. Surgery
83
Q

Describe the surgery for Crohn’s

A

Not curative
Fix strictures/fistulae
Remove as little bowel as possible

84
Q

Describe the surgery for UC

A

Can be curable
Colectomy usually
Dramatically reduces/eradicates disease process

Gastro-intestinal System (10 decks)

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