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Block D - Digestion and Metabolism > Histology Lecture 1 -- Esophagus and Stomach > Flashcards

Histology Lecture 1 -- Esophagus and Stomach Flashcards

1
Q

4 basic layers of the GI tract (from inside to outside)

A
  1. Mucosa
  2. Submucosa
  3. Tunica muscularis
  4. Adventitia / serosa
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2
Q

3 layers of the mucosa (from inside to outside)

A
  1. Epithelium
  2. Lamina propria
  3. Muscularis mucosa
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3
Q

3 types of fibres found in the lamina propria

A
  • Reticular fibres
  • Collagen
  • Elastic fibres
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4
Q

6 types of cells/structures that are often found in the lamina propria

A
  • Capillaries
  • Arterioles
  • Nerve fibers
  • Occasional fibroblasts
  • Smooth muscle cells
  • Lymphocytes
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5
Q

3 types of cells that migrate in and out of the lamina propria

A
  • Macrophages
  • Eosinophils
  • Mast cells
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6
Q

The presence of what kind of cell in the lamina propria is an indication of an abnormal condition?

A

Neutrophils (only seen within vessels)

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7
Q

Type of muscle found in the muscularis mucosa

A

Smooth muscle

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8
Q

Define the submucosa

A

A layer of connective tissue and adipose tissue that lies under the mucosa. Does not normally contain any glands (exceptions on abother flashcard)

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9
Q

Two parts of the GI tract that have glands in the submucosa, and give the name and type of these glands

A
  • Esophagus = esophageal glands
  • Duodenum = Brunner’s glands

Both = mucous glands

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10
Q

Function of the submucosa

A

Support blood vessels, lymphatics, and nerves before they enter the mucosa. Also contains nerves and ganglion cells of Meissner’s nerve plexus

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11
Q

Define the tunica muscularis

A

Thick muscular layer of the GI tract outwards of the submucosa. Usually contains 2 layers:

  1. Inner circular
  2. External longitudinal

NOTE that stomach has internal oblique followed by the usual two layers

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12
Q

Define Auerbach’s plexus

A

Nerve and ganglion cells that lie between the inner and outer muscle layers of the tunica muscularis

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13
Q

Define the peritoneum

A

A serous sac lined by simply squamous mesothelial cells and a thin layer of connective tissue, which encloses the peritoneal cavity

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14
Q

Why is the lining of the peritoneum called mesothelium instead of epithelium?

A

The cells are derived from mesoderm, but have features of epithelium

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15
Q

Define mesentery

A

A sheet-like layer of mostly loose connective tissue (containing adipose tissue, vessels and nerves going to and from gut) which is covered on both sides by mesothelium

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16
Q

Define the serosa

A

The layer of peritoneum around the gut formed by the splitting of the mesentery to encase the tubular gut

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17
Q

Define retroperitoneal histologically

A

Parts of the gut that are not completely covered by peritoneum, so the front of the gut under the peritoneum is covered by serosa and the back of the gut is covered by adventitia since it is connected to the connective tissue of the body wall

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18
Q

Where does the extrinsic nerve supply of the gut wall come from?

A

Autonomic nervous system

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19
Q

What supplies the intrinsic innervation of the gut?

A

Two plexuses which are sensory chemoreceptors or mechanoreceptors, and effectors that innervate the smooth muscle and enteroendocrine cells:

  • Myenteric (Auerbach’s) Plexus
  • Submucosal (Meissner’s) Plexus
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20
Q

Define Meissner’s Plexus

A

Ganglion cells in the submucosa

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21
Q

6 divisions of the digestive tract

A
  1. Mouth
  2. Esophagus
  3. Stomach
  4. Small intestine
  5. Large intestine
  6. Appendix
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22
Q

3 divisions of the esophagus

A
  1. Upper third
  2. Middle third
  3. Lower third
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23
Q

3 histological divisions of the stomach

A
  1. Cardiac
  2. Fundus and body
  3. Antrum and pylorus (pyloric channel)
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24
Q

3 anatomic portions of the small intestine

A
  1. Duodenum
  2. Jejunum
  3. Ileum
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25
Q

2 histological portions of the small intestine

A
  1. Duodenum
  2. Small intestine proper (includes both jejunum and ileum)
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26
Q

8 anatomic portions of the large intestine

A
  1. Cecum
  2. Ascending colon
  3. Hepatic flexure
  4. Transverse colon
  5. Splenic flexure
  6. Descending colon
  7. Sigmoid segment
  8. Rectal segment

NOTE: All the same histologically

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27
Q

Histological landmarks of the appendix

A

Colon-like mucosa, but prominent lymphoid tissue lie the terminal ileum

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28
Q

Describe the types of mucosa in the GI tract

A

Esophagus, mouth and anus = stratified squamous mucosa

Rest of the GI tract = simple columnar glandular mucosa

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29
Q

Define the precise location of the esophagus

A

Begins at a level above the cricoid cartilage and extends through the thorax in the posterior mediastinum, penetrating the diaphragm and extending a few cnetimeters in the abdomen before joining the stomach

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30
Q

How is the mucosa of the esophagus usually folded and why

A

Longitudinally so that the lumen is normally closed

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31
Q

Length of esophagus

A

23 - 25 cm long

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32
Q

Describe the tunica muscularis of the upper third portion of the esophagus

A

Skeletal muscle

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33
Q

Describe the tunica muscularis of the mid third portion of the esophagus

A

Mixture of skeletal and smooth muscle

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34
Q

Describe the tunica muscularis of the lower third portion of the esophagus

A

Smooth muscle only

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35
Q

Where are cardiac glands found?

A

Esophageal and cardiac mucosa (specifically lamina propria)

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36
Q

Where are the two groups of esophageal cardiac glands found?

A

Upper = upper third portion of esphagus at a level between the cricoid catilage of the larynx and the 5th tracheal C ring (roughly level of sternal notch)

Lower = lower third portion, at the level of the junction between the esophagus and the stomach

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37
Q

Orientation of the muscularis mucosa in the esophagus

A

Longitudinal

38
Q

Orientation of the striated muscle fibres in the esophagus

A

Non-specific (continuous with the muscles in the pharynx)

39
Q

Define Z-line in the GI tract

A

The junction of the stratified squamous epithelium with simple columber epithelium (of the stomach)

40
Q

Orientation of the muscles in the tunica muscularis of the lower third of the esophagus

A

Oblique spiral

41
Q

Describe the outermost layer of the esophagus in the lower third portion

A

Adventitia above diaphragm

Serosa between diaphgram and stomach

42
Q

Define the lower esophageal sphincter

A

2 - 4 cm zone without a wall-defined anatomical counterpart

43
Q

Function of the lower esophageal sphincter

A

Prevent reflux of gastric contents into the esophagus

44
Q

Physiologicall define the gastroesophageal junction (GE junction)

A

Lower end of the LES (therefore the lower end of the esophagus is lined by simple columnar epithelium)

45
Q

Anatomically define the gastroesophageal junction

A

The level of the peritoneal reflection from stomach to diaphragm

46
Q

Histologically define the gastroesophageal junction

A

Squamous-columnar junction (Z-line) or 2 cm above the uppermost ends of the gastric folds since these pretty much coincide

47
Q

Define the rugae of the stomach

A

Non-permanent longitudinally oriented mucosa, which are pronounced in the body and fundus of the empty stomach, but which are flattened in the distended stomach

48
Q

Define foveolae of the stomach

A

Invaginated mucosa that forms slit-like infoldings that are called pits, which vary in depth depending on the region of the stomach

49
Q

Pit:gland ratio of the cardiac region of the stomach

A

1 : 1

50
Q

Pit:gland ratio of the body region (including fundus) of the stomach

A

1:3

51
Q

Pit:gland ratio of the pyloric region of the stomach

A

2:1

52
Q

Location of cardiac region of the stomach

A

1 - 2 cm below the GE junction

53
Q

Describe the pits and glands of the cardiac and pyloric regions of the stomach

A

Pits lined by surface mucous cells

Cardiac glands secrete mucous. Divided into an isthmus and a gland proper

54
Q

Differentiate the orientation of the gastric glands from the cardiac and pyloric glands

A

Relatively straight unlike the coiled cardiac and pyloric glands

55
Q

Which layer of the tunica muscularis forms the sphincters in the stomach

A

Middle circular layer is thickened at the esophagus (LES) and pylorus (pyloric sphincter)

56
Q

Describe the features of surface mucous cells

A
  • Simple columnar cell
  • Basal nucleus is ovoid
  • Mucigen droplets form a large region in the cell apex which stains pale and often appears empty
  • Mucin secreted is neutral and PAS positive
57
Q

Describe the organization of gastric glands

A
58
Q

Define the isthmus of the stomach’s glands

A

Mouth of the glands composedof undifferentiated columnar cells that divide by mitosis and undergo renewel

59
Q

What do the surface cells give rise to?

A
  • Surface mucous cells of the crypt
  • Epithelial cells of the glands (i.e. parietal cells and mucous neck cells)
  • Zymogenic cells
60
Q

Define mucous neck cells

A

A triangular, squashed-looking cell, with the apex either at the surface or on the basal lamina, with a dark irregular nucleus at the base. Mucigen droplets fill the apex

61
Q

Where are mucous neck cells found?

A

Only in the neck region of the gastric gland

62
Q

Where are parietal cells found?

A

All levels of the gastric gland, concentrated in the isthmus portion

63
Q

Describe the histological characteristics of parietal cells

A
  • Eosinophilic
  • Large
  • Round
  • Central nucleus
  • Complex network of canaliculi filled with microvilli, lying in close association with mitochondria
64
Q

Function of parietal cells

A

Secrete HCl and gastric intrinsic factor into the stomach lumen

65
Q

What is gastric intrinsic factor required for?

A

Absorption of vitamin B12 in the ileum

66
Q

Location of zymogenic cells (chief cells)

A

May be located at all levels of the gastric gland, but tends to accumulate at the base of the gland proper

67
Q

Describe the histological features of zymogenic cells

A
  • Columnar
  • Basal ovoid nucleus
  • Basophilic end near the lamina propria
  • Eosinophilic zymogen granules in the supranuclear region
68
Q

Function of zymogenic cells

A

Secrete digestive enzymes:

  • Rennin
  • Lipase
  • Pepsin (stored in granules as pepsinogen)
69
Q

Define enteroendocrine glands

A

Unicellular endocrine glands that secrete hormones through their base into the lamina propria for distribution in the blood

70
Q

Give the proportions of the different types of enteroendocrine cells

A
  • 50% = G cells
  • 30% = EC (enterochromaffin) cells
  • 20% = others
    • D cells
    • ECL cells
71
Q

What do G cells produce?

A

Gastrin

72
Q

What is the role of gastrin?

A

Stimulate parietal cells to secrete HCl

73
Q

What do EC cells produce?

A

Serotonin

74
Q

What do D cells produce?

A

Somatostatin

75
Q

What do ECL cells produce?

A

Histamine

76
Q

5 cell types produced by the stem cells of the isthmus

A
  1. Pre-pit cells
  2. Pre-neck cells
  3. Pre-parietal cells
  4. Pre-zymogenic cells
  5. Enteroendocrine cells
77
Q

What is the surface cell turnover in the stomach?

A

48 days

78
Q

What is the base cell turnover in the stomach?

A

13 years

79
Q

Function of somatostatin in stomach

A

Inhibit the secretion of HCl by parietal cells

80
Q

Consequence of damage to parietal cells

A

Pernicious anemia

81
Q

Define mucosal associated lymphoid tissue (MALT)

A

Lymphatic nodules scattered in the stomach and bowel, located mostly in the mucosa with some extension into submucosa (may have interruptions in muscularis mucosa).

Lymphocytes are predominantly T-helper cells –> stimulate plasma cells

82
Q

Describe the epithelium of MALT

A

Cuboidal epithelial cells (M cells) with an absent basal lamina

83
Q

Function of M cells

A

Antigen presenting cells: phagocytoze antigens from the intestinal content and transport them to lymphocytes in MALT

84
Q

Importance of M cells (3)

A
  • Antigen tolerance
  • Mucosal based immunity
  • Possibly in abnormal immune conditions
85
Q

Describe the mucin secreted by esophageal cardiac glands

A

Neutral

86
Q

Describe the mucin secreted by the esophageal glands proper (submucosal)

A

Acid

87
Q

Describe the mucin secreted by the stomach surface and pit lining cells

A

Neutral (PAS positive), which are insoluble. May add to the mucosal barrier against the high acid content of the stomach

88
Q

Describe the mucin secreted by gastric glands (cardia and pylorus)

A

Protective lubricant for the stomach

89
Q

Describe the mucin secreted by mucous neck cells

A

Protective acid mucin

90
Q

Describe the mucin secreted by goblet cells in the small and large bowels

A

Acid and neutral mucins

Block D - Digestion and Metabolism (29 decks)

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