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GIGU Exam 1 > Histology Of The Stomach And Esophagus > Flashcards

Histology Of The Stomach And Esophagus Flashcards

1
Q

What three components does the mucosa of the GI tract generally contain?

A

Lining epithelium, underlying lamina propria (vascularized loose CT) with lymphatic nodules and WBC present, muscularis mucosa

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2
Q

What is muscularis mucosa?

A

A thin layer of smooth muscle that controls mobility and infoldings of the mucosa (does not participate in peristalsis)

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3
Q

What are general characteristics of submucosa?

A

Consists of dense irregular CT with neurovasculature and lymphatics
Glands may also be present (esophagus and duodenum)

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4
Q

What are some general characteristics of the muscularis externa?

A

Two layers of smooth muscle including an inner circular layer and an outer longitudinal layer
Neurovasculature plexuses reside between layers

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5
Q

Contraction of the inner circular layer of the muscularis externa causes what?

A

Construction of the gut lumen

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6
Q

Contraction of the longitudinal layer of the muscularis externa causes what?

A

Shortening of the GI tube

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7
Q

What is serosa?

A

Portion of the GI tract suspended by mesentery/peritoneum and covered by mesothelium

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8
Q

What is adventitia?

A

Areas of the GI tract without mesothelium covering it (retroperitoneal)

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9
Q

What are the 4 types of basic mucosa?

A

Protective, secretory, absorptive and absorptive/protective

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10
Q

Describe protective mucosa

A

Nonkeratinized stratified squamous epithelium

Found in oral cavity, pharynx and anal canal

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11
Q

Describe secretory mucosa

A

Simple columnar epithelium
Mucosa packed with glands
Found in stomach

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12
Q

Describe absorptive mucosa

A

Simple columnar epithelium
Mucosa arranged as villi with crypts
Glands may or may not be present (SI)

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13
Q

Describe absorptive/protective mucosa

A

Simple columnar epithelium
Mucosa closely packed
Glands with extensive goblet cells (LI)

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14
Q

Describe the esophagus

A

Fibromuscular tube that conveys food from oropharynx to stomach
Mucosal and Submucosa glands produce a thin layer of mucus to lubricate the epithelium
Cardiac esophageal glands reside in the lamina propria of terminal esophagus
Submucosal glands consist of small lobules with mucous and serous cell types

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15
Q

Describe the mucosa of the esophagus

A

Nonkeratinized stratified squamous epithelium overlying lamina propria
Numerous folds distend with food passage

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16
Q

Describe the submucosa of the esophagus

A

Network of collagen and elastic fibers with many small blood vessels
Submucosal venous plexuses drain into both the systemic and portal venous system (increased pressure can cause esophageal varices/dilation of submucosal venous sinuses)

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17
Q

The upper third esophagus has what type of muscle in the muscularis layer?

A

Skeletal muscle (striated)*

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18
Q

The middle of the esophagus has what type of muscle in the muscularis layer?

A

Skeletal and smooth*

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19
Q

The lower third of the esophagus has what type of muscle in the muscularis layer?

A

Smooth muscle*

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20
Q

What part of the esophagus contains adventitia?

A

Thoracic esophagus

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21
Q

What portion of the esophagus contains serosa?

A

Inferior to diaphragm

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22
Q

Describe the gastroesophageal junction

A

Epithelial transition from esophagus to stomach
Nonkeratinized stratified squamous —> simple columnar
Epithelium in the stomach is glandular with pits and glands

23
Q

What are rugae?

A

Longitudinal folds of the gastric mucosa that expand during filling of the stomach
Covered by gastric pits
Gastric glands produce a mucosal barrier to protect mucosal surface

24
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 mucosa facilitates release of gastric gland secretions

25
Q

Describe the submucosa of the stomach

A

Dense irregular CT with collagen and elastic fibers
Arterioles, venous plexuses and lymphatics
Meissner’s plexus

26
Q

Describe the muscularis of the stomach

A

Three layers of smooth muscle: oblique, circular and longitudinal
Circular muscle layer thickens in pyloric region forming the pyloric sphincter

27
Q

What is the final layer of the stomach?

A

Serosa made of loose CT and blood vessels

28
Q

What provides innervation to the stomach and esophagus?

A

Two plexuses of sensory and motor neurons linked by interneurons
Submucosal plexus of Meissner
Myenteric plexus of Auerbach which is between the inner circular and outer longitudinal layers of the muscularis externa

29
Q

Preganglionic axons of parasympathetics increase or decrease motility?

A

Increases

30
Q

Postganglionic axons of sympathetics increase or decrease motility?

A

Decrease

31
Q

What is the action of the two plexuses innervating the stomach and esophagus?

A

Regulate and control peristaltic contractions of muscularis externa and movements of muscularis mucosa as well as secretory activities of the mucosal and submucosal glands

32
Q

What is the lower esophageal sphincter?

A

A functional sphincter that prevents reflux of gastric contents

33
Q

What is gastroesophageal reflux disease (GERD)?

A

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

34
Q

What is Barrett’s esophagus?

A

During chronic GERD conditions nonkeratinized stratified squamous epithelium in the transition zone becomes columnar mucus secreting/glandular epithelium resulting in Barretts

35
Q

Describe fundic (gastric) glands

A

Simple branched tubular glands present throughout the gastric mucosa
Extend from bottom of gastric pits to muscularis mucosa

36
Q

What is a gastric pit?

A

Invagination of the mucosal surface (part of fundic gland)

37
Q

Describe the isthmus/neck of the fundic gland

A

Narrow region between the gastric pit and gastric gland (short and wide base)

38
Q

Describe pyloric glands

A

Branched, coiled, tubular glands of the pylorus
Lined by mucous secreting cells with large and pale secretory mucus*
Glands empty into pits that occupy half of mucosa*
Largely release gastrin from G cells
Lymphoid nodules can be seen in the lamina propria (GALT)
Occasionally parietal cells are present

39
Q

What are surface mucous cells?

A

Line the lumen and gastric pits (of fundic/gastric glands)

40
Q

What are mucous neck cells?

A

Located in the neck in singles and/or clusters (in gastric/fundic gland)
Round nuclei and apical secretory granules

41
Q

Describe mucous cells of the fundic/gastric glands

A

From a mucous layer containing 95% water and 5% mucin
Forms an insoluble gel that attaches to the surface of gastric mucosa
Thick coating that neutralizes the microenvironment to an alkaline pH

42
Q

Where are chief cells found?

A

In clusters in the inferior 1/3 of gastric glands

43
Q

What are the hallmarks of chief cells?*

A

Abundant RER and apical secretory (zymogen) granules

Basal nuclei with basophilic cytoplasm

44
Q

What do chief (zymogenic) cells secrete?

A

Pepsinogen and gastric lipase (which digests lipids)

45
Q

What is pepsinogen?

A

The proenzyme stored in secretory granules
Released and converted to pepsin by acidic environment
Proteolytic enzyme that digests most proteins
Exocytosis of pepsinogen is rapid and stimulated by feeding

46
Q

What do parietal cells produce?

A

HCl and intrinsic factor (a glycoprotein that binds to vitamin B12)

47
Q

Describe parietal cells

A

Predominate near the neck and upper segments of the gastric gland
Active parietal cells have a deep invagination of the apical plasma membrane known as an intracellular canaliculus (large surface area produced by 1000s of microvilli)

48
Q

What are the hallmarks of parietal cells?*

A

Large cells usually round or pyramidal shaped
One (sometimes two) central round nucleus
Cytoplasm is eosinophilic due to increased mitochondria

49
Q

Describe enteroendocrine cells

A

Scattered epithelial cells in the gastric mucosa named with the initial letter of their main hormone product (important for digestive function)
Most are APUD cells and process amines (amine precursor uptake and decarboxylation activity)
All generally considered part of the diffuse neuroendocrine system (DNES)
Release products that exert paracrine or endocrine effects

50
Q

What is a closed enteroendocrine cell?

A

Cellular apex i is covered by neighboring epithelial cells

Not exposed to GI lumen

51
Q

What is an open enteroendocrine cell?

A

Apical end of the cell contacts the lumen and has chemoreceptors that sample luminal contents

52
Q

What are the effects of the hormones released by enteroendocrine cells?

A

Regulation of peristalsis and motility
Secretion of digestive enzymes, water and electrolytes
Sense of being satiated after eating

53
Q

What are gastric ulcers?

A

Painful erosive lesions of the mucosa that may extend to deeper layers
Can occur anywhere between the lower esophagus and portions of the SI

54
Q

What are the causes of gastric ulcers?

A

Infections with H pylori, effects of NSAIDs, overproduction of HCl or pepsin, and lowered production or secretion of mucous or bicarbonate

GIGU Exam 1 (19 decks)

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