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GI Midterm > Histology of Esophagus and Stomach > Flashcards

Histology of Esophagus and Stomach Flashcards

1
Q

What are the four layers of the GI tract (lumen to superficial)?

A
  1. the mucosa
  2. the submucosa
  3. the muscularis externa
  4. the serosa/adventitia
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2
Q

What layer of the GI tract differs considerably from region to region?

A

mucosa - reflects functional activity

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3
Q

What is the serosa covered by?

A

peritoneum

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4
Q

Where is adventitia?

A

retroperitoneal

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5
Q

What are the 3 components of the mucosal layer?

A
  • lining epithelium (varies by segment)
  • underlying lamina propria (vascularized loose CT)
  • a thin layer of smooth muscle called muscularis mucosae
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6
Q

Where are the lymphatic nodules, lymphocytes, plasma cells, and macrophages?

A

the lamina propria of the mucosal layer of the GI tract

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7
Q

What is the function of the muscularis mucosae?

A

controls mobility of mucosa/mucosal glands

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8
Q

What is the submucosal layer comprised of?

A
  • dense irregular CT with neurovasculature and lymphatics

- glands may be present (esophagus and duodenum)

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9
Q

What makes up the muscularis externa?

A

two layers of smooth muscle

  • inner circular layer
  • outer longitudinal layer
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10
Q

What happens when the circular layer of the muscularis externa contracts?

A

constriction of the lumen

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11
Q

What happens when the longitudinal layer of the muscularis externa contracts?

A

shortens the tube

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12
Q

Where do neurovascular plexuses reside in the muscularis externa?

A

between layers

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13
Q

What is the serosa?

A

the adventitia covered by mesothelium when digestive tube is suspended by a mesentery/peritoneal fold

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14
Q

Is adventitia covered by mesothelium?

A

No, if it is covered by mesothelium it is called serosa

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15
Q

What determines if organs have adventitia or serosa?

A

depends on location

  • if it has mesothelium it is serosa
  • if no mesothelium, it is adventitia
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16
Q

What is the digestive tube innervated by?

A

extrinsic component and intrinsic component

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17
Q

What is the extrinsic component?

A

parasympathetics and sympathetics

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18
Q

What is the intrinsic component

A

enteric

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19
Q

What parasympathetics innervate GI?

A
  • vagus nerve (presynaptic) until splenic flexure
  • pelvic splanchnics (presynaptic) from splenic flexure inferiorly
  • ganglion and postsynaptic fibers are intermural
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20
Q

What sympathetics innervate GI?

A
  • branches from greater, lesser, least, and lumbar splanchnics
  • synapse in prevertebral ganglia (celiac, SM, aorticorenal, and IM ganglia)
  • postsynaptic nerves travel to organs via blood vessels on peri-arterial plexuses
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21
Q

What are the plexuses of sensory and motor neurons in the intrinsic innervation of GI?

A
  1. submucosal plexus of Meissner

2. Myenteric plexus of Auerbach

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22
Q

Where is the myenteric plexus of Auerbach?

A

between the inner circular and outer longitudinal layers (muscularis externa)

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23
Q

What is the intrinsic innervation responsive to?

A

local stimuli and input from ANS

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24
Q

What does the intrinsic innervation regulate and control?

A
  1. peristaltic contractions of muscularis externa and movements of muscularis mucosae
  2. secretory activities of the mucosal and submucosal glands
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25
Do these increase or decrease GI motility? 1. preganglionic axons of parasympathetics 2. postganglionic axons of sympathetics
1. increase | 2. decrease
26
What is the esophagus?
fibromuscular tube that conveys food from oropharynx to stomach
27
Does the esophagus have serosa or adventitia?
both
28
Where is adventitia of the esophagus?
thoracic esophagus
29
Where is the serosa of the esophagus?
inferior to diaphragm
30
What do mucosal and submucosal glands produce?
a thin layer of mucus to lubricate the epithelium
31
Where do cardiac esophageal glands reside?
in the lamina propria of terminal esophagus
32
Describe submucosal glands
small lobules with mucous and serous cell types, drained by a single duct
33
Describe the mucosa layer of the esophagus
- nonkeratinized stratified squamous overlying a lamina propria - numerous folds - muscularis muscosae is only present in lower segment
34
Describe the submucosa of the esophagus
- network of collagen and elastic fibers, many small blood vessels - submucosal venous plexuses drain into both the systemic and portal venous system
35
What causes esophageal varicies? Where? What are esophageal varicies?
- caused by increased pressure - submucosa of esophagus - dilation of the submucosal venous sinuses
36
Describe the muscularis in general, upper, middle, and lower thirds
- inner circular and outer longitudinal layers have segment dependent variations - upper third = skeletal muscle (striated) - middle third = skeletal and smooth - lower third = smooth muscle
37
What is the gastroesophageal junction?
epithelial transition from esophagus to stomach: | nonkeratinized stratified squamous to simple columnar
38
Is epithelium in the stomach glandular?
Yes, epithelium in the stomach is glandular, with pits and glands
39
What are the sphincters of the esophagus?
upper esophageal sphincter (UES) | lower esophageal sphincter (LES)
40
Is the UES anatomical or functional? What does it do?
anatomical | swallowing reflex
41
Is the LES anatomical or functional? What does it do?
functional | prevents reflux of gastric contents
42
What is GERD?
gastroesophageal reflux disease | - causes chronic inflammation, ulceration, and difficulty in swallowing (dysphagia) due to reflux of gastric contents
43
What is the medical term for difficulty swallowing?
dysphagia
44
What is Barrett's esophagus/metplasia?
chronic GERD | - nonkeratinized stratified squamous in transition zone becomes columnar muscus-secreting/glandular
45
What are the four regions of the stomach? Describe location of each.
cardia - 2-3 cm near esophageal opening fundus - projects to the left of the cardia body - an extensive central region pyloric antrum - ends at gastroduodenal orifice
46
What is the orad area of the stomach?
fundus and upper part of body that relaxes during swallowing
47
What is the caudad area of the stomach?
lower portion of the body and the antrum, participates int eh regulation of gastric emptying
48
What protects the mucosal surface?
a gastric mucosal barrier
49
What are gastric mucosal folds called? What are they covered by?
- called rugae | - covered by gastric pits
50
Describe the mucosa of the stomach
- simple columnar epithelium - lamina propria contains cardiac, gastric, and pyloric glands - reticular and collagen fibers predominate - muscularis mucosae facilitates release of gastric gland secretions
51
What fibers are predominate in the mucosa of the stomach?
reticular and collagen fibers
52
What facilitates release of gastric gland secretions in the stomach?
muscularis mucosae
53
What types of glands are in the lamina propria of the stomach?
cardiac, gastric, and pyloric glands
54
What epithelium does the mucosa of the stomach have?
simple columnar epithelium
55
Describe the submucosa of the stomach
- dense irregular CT with collagen and elastic fibers - arterioles, venous plexuses, and lymphatics - Meissner's plexus
56
Describe the muscularis/muscularis externa of the stomach
-3 layers of smooth muscle: oblique, circular, and longitudinal
57
What forms the pyloric sphincter?
circular muscle layer thickening in pyloric region in the muscularis/muscularis externa of the stomach
58
Describe the serosa of the stomach
loose CT and blood vessels
59
Does the stomach have serosa or adventitia?
serosa
60
Where are the fundic (gastric) glands?
present throughout gastric mucosa except for areas occupied by cardiac and pyloric glands
61
Describe fundic (gastric) glands
simple, branched, tubular glands - extend from bottom of gastric pits to muscularis mucosae - several open into a single gastric pit
62
What are the 3 regions of fundic (gastric) glands?
- isthmus - between gastric pit and gland below; site of stem cell niche - neck segment - narrow, relatively long region - fundic segment - shorter and wider base
63
What kind of cells are in the gastric pit, isthmus, neck, and fundus?
gastric pit: surface mucous cells isthmus: dividing and undifferentiated cells neck: mucous neck cells, parietal cells, enteroendocrine cells fundus: chief cells, enteroendocrine cells, some parietal cells
64
What do surface mucous cells secrete?
alkaline fluid containing mucin
65
What do mucous neck cells secrete?
acidic fluid containing mucin
66
What do parietal cells secrete?
intrinsic factor and hydrochloric acid
67
What do chief cells secrete?
pepsinogen and gastric lipase
68
What do G cells secrete?
gastrin into the blood
69
Where are surface mucous cells?
line the pits
70
Where are mucous neck cells?
located in the neck at the opening of the gastric gland into the pit
71
What is the mucus layer in mucous cells?
95% water, 5% mucin - forms an insoluble gel that attaches to surface of gastric mucosa - 100 micrometer thick coating that neutralizes the microenvironment to an alkaline pH
72
Where are chief cells located?
basal region of the cytoplasm containing extensive RER
73
What type of granules are in chief cells? Where?
zymogen granules | apical region
74
What is pepsinogen?
the proenzyme stored in zymogen granules - released into the lumen of gland - converted to pepsin by acid environment - proteolytic enzyme that digests most proteins - exocytosis of pepsinogen is rapid and stimulated by feeding
75
Describe parietal cells: 1. location 2. what they produce
1. predominate near neck and upper segment of the gastric gland 2. produce hydrochloric acid (of gastric juice) and intrinsic factor (a glycoprotein that binds to vitamin B12)
76
What are three distinctive features of parietal cells?
1. abundant mitochondria - produce ATP to pump H+ into secretory canaliculus 2. intracellular canaliculus - an invagination of the apical surface and continuous with the lumen of gastric gland 3. an H+, K+ dependent ATPase rich tubulovesicular system - distributed along the secretory canaliculus during the resting state
77
Describe enteroendocrine cell location
all levels of fundic glands, but more prevalent in the base
78
What are closed cells?
enteroendocrine cells: small cells that rest on the basal lamina and do not always reach the lumen - indirectly regulated by luminal content via neural and paracrine mechanisms
79
What are open cells?
enteroendocrine cells: have a thin cytoplasmic extension with microvilli and are exposed to gland lumen -chemoreceptors that sample luminal content and release hormones
80
What enteroendocrine cells are chemoreceptors that release hormones?
open cells
81
What produces gastrin? Where? | What does gastrin stimulate?
produced by G cells in pyloric antrum | stimulates production of HCl by parietal cells
82
What produces somatostatin? What is its function?
produced by D cells | inhibits gastrin action
83
What produces ghrelin? What is its function?
produced in gastric fundus - binds its receptor in pituitary and stimulates GH secretion - Ghrelin plasma levels increase during fasting to stimulate hunger
84
Describe cardiac glands
- narrow region of stomach (the cardia) that surrounds esophageal orifice - glands are tubular, coiled, and somewhat branched - opening is continuous with the gastric pits - lined with mucus secreting cells (similar to esophagus)
85
What is the hallmark of cardiac glands?
appear circular and oblique in sections
86
Describe pyloric glands
- branched, coiled, tubular glands between fundus and pylorus - glands empty into pits that occupy half of mucosa - lined by mucus-secreting cells (resemble surface mucous cells) - large and pale secretory mucus
87
What is GALT?
lymphoid notules seen in the lamina propria

GI Midterm (10 decks)

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