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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
Q

Do these increase or decrease GI motility?

  1. preganglionic axons of parasympathetics
  2. postganglionic axons of sympathetics
A
  1. increase

2. decrease

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26
Q

What is the esophagus?

A

fibromuscular tube that conveys food from oropharynx to stomach

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27
Q

Does the esophagus have serosa or adventitia?

A

both

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28
Q

Where is adventitia of the esophagus?

A

thoracic esophagus

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29
Q

Where is the serosa of the esophagus?

A

inferior to diaphragm

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30
Q

What do mucosal and submucosal glands produce?

A

a thin layer of mucus to lubricate the epithelium

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31
Q

Where do cardiac esophageal glands reside?

A

in the lamina propria of terminal esophagus

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32
Q

Describe submucosal glands

A

small lobules with mucous and serous cell types, drained by a single duct

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33
Q

Describe the mucosa layer of the esophagus

A
  • nonkeratinized stratified squamous overlying a lamina propria
  • numerous folds
  • muscularis muscosae is only present in lower segment
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34
Q

Describe the submucosa of the esophagus

A
  • network of collagen and elastic fibers, many small blood vessels
  • submucosal venous plexuses drain into both the systemic and portal venous system
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35
Q

What causes esophageal varicies?
Where?
What are esophageal varicies?

A
  • caused by increased pressure
  • submucosa of esophagus
  • dilation of the submucosal venous sinuses
36
Q

Describe the muscularis in general, upper, middle, and lower thirds

A
  • 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
Q

What is the gastroesophageal junction?

A

epithelial transition from esophagus to stomach:

nonkeratinized stratified squamous to simple columnar

38
Q

Is epithelium in the stomach glandular?

A

Yes, epithelium in the stomach is glandular, with pits and glands

39
Q

What are the sphincters of the esophagus?

A

upper esophageal sphincter (UES)

lower esophageal sphincter (LES)

40
Q

Is the UES anatomical or functional? What does it do?

A

anatomical

swallowing reflex

41
Q

Is the LES anatomical or functional? What does it do?

A

functional

prevents reflux of gastric contents

42
Q

What is GERD?

A

gastroesophageal reflux disease

- causes chronic inflammation, ulceration, and difficulty in swallowing (dysphagia) due to reflux of gastric contents

43
Q

What is the medical term for difficulty swallowing?

A

dysphagia

44
Q

What is Barrett’s esophagus/metplasia?

A

chronic GERD

- nonkeratinized stratified squamous in transition zone becomes columnar muscus-secreting/glandular

45
Q

What are the four regions of the stomach? Describe location of each.

A

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
Q

What is the orad area of the stomach?

A

fundus and upper part of body that relaxes during swallowing

47
Q

What is the caudad area of the stomach?

A

lower portion of the body and the antrum, participates int eh regulation of gastric emptying

48
Q

What protects the mucosal surface?

A

a gastric mucosal barrier

49
Q

What are gastric mucosal folds called? What are they covered by?

A
  • called rugae

- covered by gastric pits

50
Q

Describe the mucosa of the stomach

A
  • 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
Q

What fibers are predominate in the mucosa of the stomach?

A

reticular and collagen fibers

52
Q

What facilitates release of gastric gland secretions in the stomach?

A

muscularis mucosae

53
Q

What types of glands are in the lamina propria of the stomach?

A

cardiac, gastric, and pyloric glands

54
Q

What epithelium does the mucosa of the stomach have?

A

simple columnar epithelium

55
Q

Describe the submucosa of the stomach

A
  • dense irregular CT with collagen and elastic fibers
  • arterioles, venous plexuses, and lymphatics
  • Meissner’s plexus
56
Q

Describe the muscularis/muscularis externa of the stomach

A

-3 layers of smooth muscle: oblique, circular, and longitudinal

57
Q

What forms the pyloric sphincter?

A

circular muscle layer thickening in pyloric region in the muscularis/muscularis externa of the stomach

58
Q

Describe the serosa of the stomach

A

loose CT and blood vessels

59
Q

Does the stomach have serosa or adventitia?

A

serosa

60
Q

Where are the fundic (gastric) glands?

A

present throughout gastric mucosa except for areas occupied by cardiac and pyloric glands

61
Q

Describe fundic (gastric) glands

A

simple, branched, tubular glands

  • extend from bottom of gastric pits to muscularis mucosae
  • several open into a single gastric pit
62
Q

What are the 3 regions of fundic (gastric) glands?

A
  • 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
Q

What kind of cells are in the gastric pit, isthmus, neck, and fundus?

A

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
Q

What do surface mucous cells secrete?

A

alkaline fluid containing mucin

65
Q

What do mucous neck cells secrete?

A

acidic fluid containing mucin

66
Q

What do parietal cells secrete?

A

intrinsic factor and hydrochloric acid

67
Q

What do chief cells secrete?

A

pepsinogen and gastric lipase

68
Q

What do G cells secrete?

A

gastrin into the blood

69
Q

Where are surface mucous cells?

A

line the pits

70
Q

Where are mucous neck cells?

A

located in the neck at the opening of the gastric gland into the pit

71
Q

What is the mucus layer in mucous cells?

A

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
Q

Where are chief cells located?

A

basal region of the cytoplasm containing extensive RER

73
Q

What type of granules are in chief cells? Where?

A

zymogen granules

apical region

74
Q

What is pepsinogen?

A

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
Q

Describe parietal cells:

  1. location
  2. what they produce
A
  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
Q

What are three distinctive features of parietal cells?

A
  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
Q

Describe enteroendocrine cell location

A

all levels of fundic glands, but more prevalent in the base

78
Q

What are closed cells?

A

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
Q

What are open cells?

A

enteroendocrine cells: have a thin cytoplasmic extension with microvilli and are exposed to gland lumen
-chemoreceptors that sample luminal content and release hormones

80
Q

What enteroendocrine cells are chemoreceptors that release hormones?

A

open cells

81
Q

What produces gastrin? Where?

What does gastrin stimulate?

A

produced by G cells in pyloric antrum

stimulates production of HCl by parietal cells

82
Q

What produces somatostatin? What is its function?

A

produced by D cells

inhibits gastrin action

83
Q

What produces ghrelin? What is its function?

A

produced in gastric fundus

  • binds its receptor in pituitary and stimulates GH secretion
  • Ghrelin plasma levels increase during fasting to stimulate hunger
84
Q

Describe cardiac glands

A
  • 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
Q

What is the hallmark of cardiac glands?

A

appear circular and oblique in sections

86
Q

Describe pyloric glands

A
  • 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
Q

What is GALT?

A

lymphoid notules seen in the lamina propria

GI Midterm (10 decks)

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