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Tissue biology > Lecture 6: The lower GI tract > Flashcards

Lecture 6: The lower GI tract Flashcards

(75 cards)

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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
What do neuroendocrine cells produce?
Locally acting hormones
26
Where are stem cells found within the small intestine?
At the base of crypts
27
What do stem cells in the small intestine do?
Divide to replenish other cell types
28
What is another type of cell found within the small intestine, no mentioned above?
Intraepithelial lymphocytes
29
What is the function of the glycocalyx?
To provide additional surface for adsorption
30
What does the glycocalyx consist of?
Acidic mucopolysaccharides and glycoproteins
31
What do the acidic mucopolysaccharides and glycoproteins of the glycocalyx project from?
Apical plasma membrane of epithelial absorptive cells
32
What enzyme are included in the glycocalyx?
Enzymes secreted by absorptive cells, essential for final steps of protein and sugar digestion
33
What are the two regions of cells that make up the small intestinal crypt?
Terminally differentiated cells | Transit amplifying cells
34
What does APUD stand for?
Amine and precursor uptake and decarboxylation
35
What does APUD mean?
A collective term for a range of endocrine cells throughout the body
36
What are APUD cells a component of?
A universal diffuse neuroendocrine system
37
How can APUD cells be identified histologically?
Their staining behaviour (chromogranin A)
38
What are the three site specific anatomical features of the duodenum?
Brunner's glands No plicae circulares Meissner's plexus
39
What did Johann Conrad Brunner notice when he removed the pancreas from a dog?
The animal experienced extreme thirst and polyuria
40
What do Brunner's glands produce?
Alkaline mucus to neutralize acid content enter duodenum from stomach
41
What is the shape of a brunner's gland?
Compound, tubular mucous glands
42
Where are brunner's glands located within the layers of the duodenum?
Submucosa | They fill this region completely that the typical submucosal connective tissue is obscured
43
In what way do Brunner's glands represent a continuation of the pyloric glands of the stomach?
At pyloric junction, mucous glands of the pyloric mucosa are replaced by Brunner's glands of the duodenal submucosa
44
What does the Meissner's plexus comprise a network of?
Unmyelinated nerve fibres and associated ganglia
45
What is Meissner's plexus also called?
Submucosal plexus
46
What part of the nervous system is Meissner's plexus ?
Autonomic nervous system
47
In the jejunum and ileum, the majority of cells in crypt bases are what?
Stem cells
48
What part of the immune system are paneth cells part of
Innate immune system
49
What make up the paneth cells?
Anti-microbial peptides (defensins) | Protective enzymes
50
What are protective enzymes found in paneth cells?
Phospholipase A and lysozyme
51
How long lived are paneth cells vs enterocytes and goblet cells?
Paneth cells: weeks | Enterocytes/goblet cells: 3-5 days
52
What type of hormones do endocrine cells in the jejunum and ileum secrete?
Secretin, serotonin, somatostatin
53
What are the villi length on the jejunum vs the ileum?
Longer villi in jejunum, shorter in ileum
54
What is found between the longitudinal and circular layers of the muscularis propria in the duodenum?
Auerbach's (myenteric) plexus
55
How does the proprotion of goblet cells vary in the small intestine?
Increases distally
56
Where are plicae circulares absent?
Proximal duodenum and distal ileum
57
Name the valve
Ileocaecal valve
58
What villi are found in the large intestine?
No villi
59
What is the appendix?
Blind-ended tubular sac attached to caecum
60
What is the appendix part of?
Large intestine
61
What is found in the submucosa of the appendix?
Masses of lymphoid tissue
62
How are glands spaced in the appendix compared to elsewhere in the large intestine?
Spaced more widely
63
What are the 4 regions of the large intestine?
``` Ascending colon Transverse colon Descending colon Sigmoid colon Rectum ```
64
How long is the large intestine?
1.5m (1/5 whole length intestinal canal)
65
What does the large intestine absorb from the 1.5L of chyme passing through daily?
Water and electrolytes
66
What vitamins does the large intestine absorb?
K, B12, thiamine, riboflavin
67
What is the function, other than absorbtion, of the large intestine?
Compacts faeces, stores fecal matter in rectum
68
What does the colon do
Recover water, peristalsis of faecal material (thick muscular wall)
69
What cells are found in the colon?
Absoptive and mucus-secreting cells
70
What else is found in the colon?
Commensal bacteria
71
What does Auerbach's plexus do?
Regulate peristaltic contractions by nerve fibres located between circular and longitudinal layers of muscle
72
What is the rectum?
Dilated distal part of large bowel
73
How is rectal mucosa different to the rest of the large bowel?
More goblet cells
74
What happens at the recto-anal junction?
Abrupt transition to stratified squamous epithelium followed by gradual transition to skin
75
What surrounds the anal canal?
Skeletal muscle and anal sphincter

Tissue biology (7 decks)

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