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

Histology Lecture 1 -- Esophagus and Stomach Flashcards

(90 cards)

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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
2 histological portions of the small intestine
1. Duodenum 2. Small intestine proper (includes both jejunum and ileum)
26
8 anatomic portions of the large intestine
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
27
Histological landmarks of the appendix
Colon-like mucosa, but prominent lymphoid tissue lie the terminal ileum
28
Describe the types of mucosa in the GI tract
Esophagus, mouth and anus = stratified squamous mucosa Rest of the GI tract = simple columnar glandular mucosa
29
Define the precise location of the esophagus
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
30
How is the mucosa of the esophagus usually folded and why
Longitudinally so that the lumen is normally closed
31
Length of esophagus
23 - 25 cm long
32
Describe the tunica muscularis of the upper third portion of the esophagus
Skeletal muscle
33
Describe the tunica muscularis of the mid third portion of the esophagus
Mixture of skeletal and smooth muscle
34
Describe the tunica muscularis of the lower third portion of the esophagus
Smooth muscle only
35
Where are cardiac glands found?
Esophageal and cardiac mucosa (specifically lamina propria)
36
Where are the two groups of esophageal cardiac glands found?
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
37
Orientation of the muscularis mucosa in the esophagus
Longitudinal
38
Orientation of the striated muscle fibres in the esophagus
Non-specific (continuous with the muscles in the pharynx)
39
Define Z-line in the GI tract
The junction of the stratified squamous epithelium with simple columber epithelium (of the stomach)
40
Orientation of the muscles in the tunica muscularis of the lower third of the esophagus
Oblique spiral
41
Describe the outermost layer of the esophagus in the lower third portion
Adventitia above diaphragm Serosa between diaphgram and stomach
42
Define the lower esophageal sphincter
2 - 4 cm zone without a wall-defined anatomical counterpart
43
Function of the lower esophageal sphincter
Prevent reflux of gastric contents into the esophagus
44
Physiologicall define the gastroesophageal junction (GE junction)
Lower end of the LES (therefore the lower end of the esophagus is lined by simple columnar epithelium)
45
Anatomically define the gastroesophageal junction
The level of the peritoneal reflection from stomach to diaphragm
46
Histologically define the gastroesophageal junction
Squamous-columnar junction (Z-line) or 2 cm above the uppermost ends of the gastric folds since these pretty much coincide
47
Define the rugae of the stomach
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
Define foveolae of the stomach
Invaginated mucosa that forms slit-like infoldings that are called pits, which vary in depth depending on the region of the stomach
49
Pit:gland ratio of the cardiac region of the stomach
1 : 1
50
Pit:gland ratio of the body region (including fundus) of the stomach
1:3
51
Pit:gland ratio of the pyloric region of the stomach
2:1
52
Location of cardiac region of the stomach
1 - 2 cm below the GE junction
53
Describe the pits and glands of the cardiac and pyloric regions of the stomach
Pits lined by surface mucous cells Cardiac glands secrete mucous. Divided into an isthmus and a gland proper
54
Differentiate the orientation of the gastric glands from the cardiac and pyloric glands
Relatively straight unlike the coiled cardiac and pyloric glands
55
Which layer of the tunica muscularis forms the sphincters in the stomach
Middle circular layer is thickened at the esophagus (LES) and pylorus (pyloric sphincter)
56
Describe the features of surface mucous cells
* 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
Describe the organization of gastric glands
58
Define the isthmus of the stomach's glands
Mouth of the glands composedof undifferentiated columnar cells that divide by mitosis and undergo renewel
59
What do the surface cells give rise to?
* Surface mucous cells of the crypt * Epithelial cells of the glands (i.e. parietal cells and mucous neck cells) * Zymogenic cells
60
Define mucous neck cells
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
Where are mucous neck cells found?
Only in the neck region of the gastric gland
62
Where are parietal cells found?
All levels of the gastric gland, concentrated in the isthmus portion
63
Describe the histological characteristics of parietal cells
* Eosinophilic * Large * Round * Central nucleus * Complex network of canaliculi filled with microvilli, lying in close association with mitochondria
64
Function of parietal cells
Secrete HCl and gastric intrinsic factor into the stomach lumen
65
What is gastric intrinsic factor required for?
Absorption of vitamin B12 in the ileum
66
Location of zymogenic cells (chief cells)
May be located at all levels of the gastric gland, but tends to accumulate at the base of the gland proper
67
Describe the histological features of zymogenic cells
* Columnar * Basal ovoid nucleus * Basophilic end near the lamina propria * Eosinophilic zymogen granules in the supranuclear region
68
Function of zymogenic cells
Secrete digestive enzymes: * Rennin * Lipase * Pepsin (stored in granules as pepsinogen)
69
Define enteroendocrine glands
Unicellular endocrine glands that secrete hormones through their base into the lamina propria for distribution in the blood
70
Give the proportions of the different types of enteroendocrine cells
* 50% = G cells * 30% = EC (enterochromaffin) cells * 20% = others * D cells * ECL cells
71
What do G cells produce?
Gastrin
72
What is the role of gastrin?
Stimulate parietal cells to secrete HCl
73
What do EC cells produce?
Serotonin
74
What do D cells produce?
Somatostatin
75
What do ECL cells produce?
Histamine
76
5 cell types produced by the stem cells of the isthmus
1. Pre-pit cells 2. Pre-neck cells 3. Pre-parietal cells 4. Pre-zymogenic cells 5. Enteroendocrine cells
77
What is the surface cell turnover in the stomach?
48 days
78
What is the base cell turnover in the stomach?
13 years
79
Function of somatostatin in stomach
Inhibit the secretion of HCl by parietal cells
80
Consequence of damage to parietal cells
Pernicious anemia
81
Define mucosal associated lymphoid tissue (MALT)
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
Describe the epithelium of MALT
Cuboidal epithelial cells (M cells) with an absent basal lamina
83
Function of M cells
Antigen presenting cells: phagocytoze antigens from the intestinal content and transport them to lymphocytes in MALT
84
Importance of M cells (3)
* Antigen tolerance * Mucosal based immunity * Possibly in abnormal immune conditions
85
Describe the mucin secreted by esophageal cardiac glands
Neutral
86
Describe the mucin secreted by the esophageal glands proper (submucosal)
Acid
87
Describe the mucin secreted by the stomach surface and pit lining cells
Neutral (PAS positive), which are insoluble. May add to the mucosal barrier against the high acid content of the stomach
88
Describe the mucin secreted by gastric glands (cardia and pylorus)
Protective lubricant for the stomach
89
Describe the mucin secreted by mucous neck cells
Protective acid mucin
90
Describe the mucin secreted by goblet cells in the small and large bowels
Acid and neutral mucins

Block D - Digestion and Metabolism (29 decks)

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