Histology of the Esophagus and Stomach Flashcards

1
Q

Organization of the GI tract

A

mucosa
submucosa
muscularis externa
serosa/adventitia

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2
Q

Mucosal Layer

A

Three components!

  • lining epithelium (varies segment to segment)
  • underlying lamina propria (vascularized loose CT has lymphatic nodules, lymphocytes, plasma cells, macrophages)
  • muscularis mucosae (this smooth m) –> controls mobility of mucosa/mucosal glands
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3
Q

submucosal layer

A
  • dense irregular CT w/ neurovasculature and lymphatics

- glands may also be present (esophagus/duodenum)

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4
Q

Muscularis Externa

A

two layers of smooth muscle (inner circular/outer longitudinal)
-contraction of circular =constricts lumen
-contraction of longitudinal=shortens tube
neurovascular plexuses reside between layers

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5
Q

Serosa/Adventitia

A

When digested tube is suspended by a mesentery/periotneal fold= covered by mesothelium=serosa
-no mesothelium?=adventitia
you can have either or/or both!

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6
Q

GI innervation

A

extrinsic-para and symp

intrinsic=enteric

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7
Q

Parasympathetics of GI

A
vagus nerve (until splenic fixure)
pelvic splanchnic (splenic flexure --> inferiorly
fibers in vagus and pelvic splanchnics are presynaptic
ganglion and post synaptic fibers are intramural
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8
Q

Sympathetics of 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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9
Q

Intrinsic Innvervation

A

two plexuses of sensory and motor linked by interneurons

1) submucosal plexus of meissner-found in submucosa and is responsible for regulating secretion of glands in submucosa
2) myenteric plexus of auerbach-between inner circ and outer long. layers (lighter stained)

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10
Q

Myenteria/Meissner

A

responsive to local stimuli and input from ANS
regulate and control:
1)peristaltic contractions of muscularis externa and movements of muscularis mucosae
2) secretory activities of the mucosal and submucosal glands

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11
Q

Esophagus

A

fibromuscular tube that conveys food from oropharynx to stomach
thoracic eso: adventitia
inferior to diaphragm=serosa
TWO GLANDS: cardiac/submucosal

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12
Q

Cardiac Esophageal glands

A

produce a thin layer of mucus to lubricate the epi.

reside in the lamina propria of terminal esophagus

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13
Q

submucosal glands

A

produce a thin layer of mucus to lubricate the epi.

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

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14
Q

Gastroesophageal junction

A

epithelial transition from esophagus to stomach
nonkeratinized stratified squamous –> simple columnar
epi. in the stomach is glandular, with pits and glands

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15
Q

Sphincters of Esophagus

A

Upper esophageal sphincter: anatomical, swallowing reflex
lower esophageal sphincter: functional, prevents reflex of gastric contents (designed to be closed down so acid components dont move superiorly)

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16
Q

Gastroesophageal reflux disease (GERD)

A

causes chronic inflammation, ulceration, and difficulty swallowing (dysphagia) due to reflex of gastric contents
-loosening of sphincter causes backflow of acid

17
Q

Barret’s Esophagus

A

chronic
nonkeratinized stratified squamous in transition zone –> becomes columnar mucus-secreting/glandular, barret’s esophagus/metaplasia

18
Q

Regions of stomach

A

cardia: 2-3 cm near esophageal opening
fundus: projects to the left of the cardia
body: extensive central region
pyloric antrum: ends at gastroduodenal orifice

19
Q

Orad area

A

fundus and upper part of the body, relaxes during swallowing

LES area

20
Q

caudad area

A

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

21
Q

Rugae

A

gastric mucosal folds/ridges that mix food and break it down. IT helps to increase friction and break down internal food components.
in mucosa/submucosa
-covered by gastric pits

22
Q

Fundic (gastric) glands

A

present throughout gastric mucosa except for areas occupied by cardiac and pyloric glands
-simple branched tubular glands (extend from bottom of gastric pits –> muscularis muscosae) (several open into a single gastric pit)

23
Q

Gastric gland: isthmus

A

between gastric pit and gland below
site of stem cell niche
-dividing and undifferentiated cells (connector region of functional component of gland to gastric pit)

24
Q

gastric gland: neck segment

A

narrow, relatively long region
mucous neck cells (secrete mucus)
parietal cells
enteroendocrine cells

25
Q

gastric gland: fundic segment

A

shorter and wider base
-chief cells
-enteroendocrine cells
some parietal cells

26
Q

Mucous cells

A

a mucus layer, containing 95% water, 5% mucin

  • forms an insoluble gel that attaches to surface of gastric mucosa
  • 100 um thick coating that neutralizes the microenvironment to an alkaline pH
27
Q

surface mucous cells

A

line the pits (insoluble)
have apical granules containing mucins.
has abundant mito, and carbonic anhydrase contribute to the formation of bicarbonate ions –> increase pH

28
Q

mucous neck cells

A

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

29
Q

Chief cells

A

basal region of the cytoplasms contains extensive RER

numerous zymogen granules are located in apical region. release contents via exocytosis

30
Q

Pepsinogen

A

proenzyme stored in the zymogen granules

  • released into the lumen of the gland
  • converted to pepsin by acid enviroment
  • proteolytic enzyme that digests most proteins
  • exocytosis of pepsinogen is rapid and simulated by feeding
31
Q

Enteroendocrine cells

A

have two types of cells: closed cells and open cells

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

32
Q

Closed cells of enteroendocrine cells

A

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

33
Q

Open cells of enteroendocrine cells

A

have a thin cytoplasmic extension w/ microvilli and are exposed to gland lumen
-chemoreceptors that sample luminal contents and release hormones

34
Q

Gastrin

A

produced by G cells in pyloric antrum

  • stimulates production of HCL by parietal cells
  • released in stomach, duodenum, jejunum
35
Q

somatostatin

A

produced by D cells

  • inhibits gastrin action
  • throughout entire GI tract
36
Q

ghrelin

A

produced in gastric fundus
-binds its receptor in pituitary and stimulates GH secretion
-Ghrelin plasma levels increase during fasting –> triggers hunger
released in fundus

37
Q

Cardiac Glands of Stomach

A

narrow region of stomach (the cardia) that surrounds the esophageal orifice
-glands are tubular, coiled and somewhat branched
-opening is continuous with the gastric pits
-lined with mucus-secreting cells
Hallmark: appear circular and oblique in sections

38
Q

Pyloric Glands of stomach

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
occasional enteroendocrine cells and parietal cells are present; GALT in lamina propria