Lecture 6: The lower GI tract Flashcards

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1
Q

What are the three regions of the small intestine?

A

Dueodenum
Jejunum
Ileum

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2
Q

What is the length of the duodenum?

A

25-30cm

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3
Q

What is the length of the jejunum?

A

2.5 metres

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4
Q

What is the length of the ileum?

A

3.5 metres

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5
Q

What is the principal function of the small intestine?

A

Absorption and digestion of products

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6
Q

How long is the small intestine in adults?

A

4-6m

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7
Q

What is the name of the folds of the mucosa and submucosa in the small intestine?

A

Plicae circulares

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8
Q

What are the finger-like projections in the small intestine?

A

Villi

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9
Q

What structure on the enterocytes increases surface area?

A

Microvilli

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10
Q

Where are lymphoid aggregations found within the layers of the small intestine?

A

Lamina propria

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11
Q

What name is given to the 200+ lymphoid aggregations in the small intestine’s lamina propria?

A

Peyer’s patches

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12
Q

What shape are Peyer’s patches?

A

Groups of lymphoid follicles which bulge ‘dome-like’ into the lumen

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13
Q

Where along the small intestine are Peyer’s patches most prominent and least prominent?

A

Fewest in duodenum

Most in terminal ileum

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14
Q

What is located in the germinal center of a Peyer’s patch?

A

Proliferating and maturing B cells, surrounded by mantle of resting lymphocytes

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15
Q

What makes up the area between follicles in peyer’s patches?

A

T lymphocytes

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16
Q

What is the specialised follicular epithelium overlying peyer’s patches specialised for?

A

Anitgen uptake

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17
Q

What do M cells in Peyer’s patches do?

A

Act as bacterial sensors, activating the immune system

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18
Q

Peyer’s patches are connected to what type of lymph node?

A

Mesenteric lymph node

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19
Q

What type of cell lines the small intestine?

A

Simple columnar epithelium

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20
Q

What is the most common type of cell in the small intestine?

A

Enterocytes

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21
Q

What is the structure of the enterocyte cells?

A

Tall columnar

Surface microvilli

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22
Q

What do goblet cells in the small intestine produce?

A

Mucin

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23
Q

What cells are found at the base of crypts in the small intestine?

A

Paneth cells

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24
Q

What do paneth cells contain/

A

Eosinophilic apical granules

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25
Q

What do neuroendocrine cells produce?

A

Locally acting hormones

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26
Q

Where are stem cells found within the small intestine?

A

At the base of crypts

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27
Q

What do stem cells in the small intestine do?

A

Divide to replenish other cell types

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28
Q

What is another type of cell found within the small intestine, no mentioned above?

A

Intraepithelial lymphocytes

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29
Q

What is the function of the glycocalyx?

A

To provide additional surface for adsorption

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30
Q

What does the glycocalyx consist of?

A

Acidic mucopolysaccharides and glycoproteins

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31
Q

What do the acidic mucopolysaccharides and glycoproteins of the glycocalyx project from?

A

Apical plasma membrane of epithelial absorptive cells

32
Q

What enzyme are included in the glycocalyx?

A

Enzymes secreted by absorptive cells, essential for final steps of protein and sugar digestion

33
Q

What are the two regions of cells that make up the small intestinal crypt?

A

Terminally differentiated cells

Transit amplifying cells

34
Q

What does APUD stand for?

A

Amine and precursor uptake and decarboxylation

35
Q

What does APUD mean?

A

A collective term for a range of endocrine cells throughout the body

36
Q

What are APUD cells a component of?

A

A universal diffuse neuroendocrine system

37
Q

How can APUD cells be identified histologically?

A

Their staining behaviour (chromogranin A)

38
Q

What are the three site specific anatomical features of the duodenum?

A

Brunner’s glands
No plicae circulares
Meissner’s plexus

39
Q

What did Johann Conrad Brunner notice when he removed the pancreas from a dog?

A

The animal experienced extreme thirst and polyuria

40
Q

What do Brunner’s glands produce?

A

Alkaline mucus to neutralize acid content enter duodenum from stomach

41
Q

What is the shape of a brunner’s gland?

A

Compound, tubular mucous glands

42
Q

Where are brunner’s glands located within the layers of the duodenum?

A

Submucosa

They fill this region completely that the typical submucosal connective tissue is obscured

43
Q

In what way do Brunner’s glands represent a continuation of the pyloric glands of the stomach?

A

At pyloric junction, mucous glands of the pyloric mucosa are replaced by Brunner’s glands of the duodenal submucosa

44
Q

What does the Meissner’s plexus comprise a network of?

A

Unmyelinated nerve fibres and associated ganglia

45
Q

What is Meissner’s plexus also called?

A

Submucosal plexus

46
Q

What part of the nervous system is Meissner’s plexus ?

A

Autonomic nervous system

47
Q

In the jejunum and ileum, the majority of cells in crypt bases are what?

A

Stem cells

48
Q

What part of the immune system are paneth cells part of

A

Innate immune system

49
Q

What make up the paneth cells?

A

Anti-microbial peptides (defensins)

Protective enzymes

50
Q

What are protective enzymes found in paneth cells?

A

Phospholipase A and lysozyme

51
Q

How long lived are paneth cells vs enterocytes and goblet cells?

A

Paneth cells: weeks

Enterocytes/goblet cells: 3-5 days

52
Q

What type of hormones do endocrine cells in the jejunum and ileum secrete?

A

Secretin, serotonin, somatostatin

53
Q

What are the villi length on the jejunum vs the ileum?

A

Longer villi in jejunum, shorter in ileum

54
Q

What is found between the longitudinal and circular layers of the muscularis propria in the duodenum?

A

Auerbach’s (myenteric) plexus

55
Q

How does the proprotion of goblet cells vary in the small intestine?

A

Increases distally

56
Q

Where are plicae circulares absent?

A

Proximal duodenum and distal ileum

57
Q

Name the valve

A

Ileocaecal valve

58
Q

What villi are found in the large intestine?

A

No villi

59
Q

What is the appendix?

A

Blind-ended tubular sac attached to caecum

60
Q

What is the appendix part of?

A

Large intestine

61
Q

What is found in the submucosa of the appendix?

A

Masses of lymphoid tissue

62
Q

How are glands spaced in the appendix compared to elsewhere in the large intestine?

A

Spaced more widely

63
Q

What are the 4 regions of the large intestine?

A
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
64
Q

How long is the large intestine?

A

1.5m (1/5 whole length intestinal canal)

65
Q

What does the large intestine absorb from the 1.5L of chyme passing through daily?

A

Water and electrolytes

66
Q

What vitamins does the large intestine absorb?

A

K, B12, thiamine, riboflavin

67
Q

What is the function, other than absorbtion, of the large intestine?

A

Compacts faeces, stores fecal matter in rectum

68
Q

What does the colon do

A

Recover water, peristalsis of faecal material (thick muscular wall)

69
Q

What cells are found in the colon?

A

Absoptive and mucus-secreting cells

70
Q

What else is found in the colon?

A

Commensal bacteria

71
Q

What does Auerbach’s plexus do?

A

Regulate peristaltic contractions by nerve fibres located between circular and longitudinal layers of muscle

72
Q

What is the rectum?

A

Dilated distal part of large bowel

73
Q

How is rectal mucosa different to the rest of the large bowel?

A

More goblet cells

74
Q

What happens at the recto-anal junction?

A

Abrupt transition to stratified squamous epithelium followed by gradual transition to skin

75
Q

What surrounds the anal canal?

A

Skeletal muscle and anal sphincter