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Histology - Exam 3 > Digestive System - Upper > Flashcards

Digestive System - Upper Flashcards

1
Q

contents of digestive system

A

oral cavity and alimentary canal:

  • esophagus
  • stomach
  • small and large intestines
  • extrinsic glands
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2
Q

describe digestive tract and name the 4 layers

A

layered hollow tube:

  1. mucosa
  2. submucosa
  3. muscularis externa
  4. serosa (where continuous w/ mesentery) or adventitia (where fixed to wall of cavity)
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3
Q

function of digestive system

A

secrete enzymes and hormones that function in digestive process

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4
Q

epithelium of esophagus

A

stratified squamous nonkeratinized epithelium

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5
Q

glands of esophagus

A
  • esophageal cardiac glands

- esophageal glands proper

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6
Q

esophageal cardiac gland secretion

A

mucus-secreting

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7
Q

esophageal cardiac gland location

A

in lamina propria, at top and bottom of esophagus (mainly top), but not super abundant

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8
Q

what are esophageal cardiac glands similar to?

A

cardiac glands in stomach

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9
Q

esophageal glands proper secretion

A

primarily mucus secreting, but also some serous cells that secrete lysozyme

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10
Q

esophageal glands proper location

A

in submucosa

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11
Q

muscularis mucosae

A

single longitudinal layer of smooth muscle

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12
Q

how does the muscularis externa change as you move proximal to distal in the esophagus?

A
  • upper third = striated, skeletal muscle
  • middle third = outer layer of smooth muscle, inner layer of skeletal muscle
  • lower third = smooth muscle
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13
Q

function of esophagus

A

conveys food (bolus) from pharynx to stomach by the peristaltic activity of the muscularis externa

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14
Q

what are the two sphincters in the muscularis externa?

A
  • upper = pharyngoesophageal

- lower = gastroesophageal

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15
Q

overall function of the two sphincters of esophagus

A

ensures bolus transported in one direction only - toward stomach

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16
Q

function of the upper esophageal sphincter (UES)

A

initiates swallowing

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17
Q

function of the lower esophageal sphincter (LES)

A

prevents acid reflux from stomach into esophagus

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18
Q

GERD and cause

A

gastroesophageal reflux disease - caused by persistent acid reflux

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19
Q

what can acid reflux from stomach into esophagus lead to?

A

ulceration and dysphagia - ultimately can lead to fibrosis and stricture of the lower esophagus

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20
Q

Barrett’s esophagus

A
  • abnormal growth growth of intestinal-type cells (simple columnar) in the lower esophagus
  • more easily injured by stomach acid
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21
Q

what is Barrett’s esophagus a risk factor for?

A

adenocarcinoma of esophagus

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22
Q

what sex does Barrett’s esophagus present in more?

A

3x more incidence in males

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23
Q

hiatal hernia

A

portion of stomach that can move into thoracic cavity

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24
Q

what causes hiatal hernia?

A

if esophageal hiatus in diaphragm does not close entirely during development

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25
Q

what can result from hiatal hernia?

A

reflux esophagitis and ulceration - difficulty swallowing and a feeling of a lump in the throat

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26
Q

function of the stomach

A

acidifies and converts food into viscous fluid called chyme

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27
Q

what does the stomach produce?

A

digestive enzymes and hormones

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28
Q

rugae

A

longitudinal folds of the mucosa and submucosa that disappear in distended stomach

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29
Q

describe gastric pits in the different parts of the stomach

A

deepest in pylorus and shallowest in cardia

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30
Q

what are gastric pits?

A

entrance to gastric glands

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31
Q

regions of stomach

A
  • cardia
  • fundus
  • body
  • pylorus
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32
Q

cardia

A
  • tubular glands with coiled end

- mucus secreting

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33
Q

fundus

A
  • simple tubular glands
  • shallow gastric gland pits
  • abundant parietal and chief cells
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34
Q

what section of stomach is the primary contributor to gastric juice?

A

fundus

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35
Q

body of stomach

A

similar to fundus

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36
Q

pylorus

A
  • deep gastric pits
  • branched glands
  • primarily mucus secreting
  • occasional parietal cell
  • gastrin secreting G cells
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37
Q

lining of gastric mucosa

A

mucus-producing simple columnar surface lining cells (NOT goblet cells)

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38
Q

lamina propria of gastric mucosa

A

loose CT containing:

  • smooth muscle cells
  • lymphocytes
  • plasma cells
  • mast cells
  • fibroblasts
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39
Q

what type of glands does the gastric mucosa contain?

A

gastric glands

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40
Q

muscularis mucosae of gastric mucosa

A
  • poorly defined inner circular layer
  • outer longitudinal layer of smooth muscle
  • occasionally an outermost circular layer
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41
Q

contents of gastric mucosa

A
  • epithelium
  • lamina propria
  • gastric glands
  • muscularis mucosae
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42
Q

composition of gastric submucosa

A
  • dense irregular collagenous CT
  • fibroblasts
  • mast cells
  • lymphoid elements
  • Meissner’s plexus
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43
Q

composition of gastric muscularis externa

A

3 layers of smooth muscle:

  • incomplete inner oblique
  • thick middle circular
  • outer longitudinal
44
Q

which layer of gastric muscularis externa forms the pyloric sphincter?

A

thick middle circular layer

45
Q

function of gastric muscularis externa

A

mixing gastric contents and stomach emptying

46
Q

what influences rate of stomach emptying?

A

chyme characteristics:

  • viscosity
  • pH
  • lipid content
  • osmolality
  • caloric density
47
Q

gastric serosa

A

covers the external surface of the stomach

48
Q

epithelium of fundus and body region

A

mucus-secreting surface lining cells

49
Q

parts of gastric glands

A

isthmus, neck, and base

50
Q

isthmus of gastric glands

A

connects gland to the base of a gastric pit

51
Q

what types of cells do gastric glands have?

A

parietal, chief. mucous neck, enteroendocrine

-also have regenerative cells

52
Q

regenerative cells

A

replace all other cells in the gland, pit and luminal surface - located primarily in neckand isthmus

53
Q

what do surface-lining simple columnar cells contain?

A

apically located mucinogen granules

54
Q

what do surface-lining simple columnar cells secrete?

A

cloudy, thick, viscous mucus with high bicarbonate content (acid protection) - coats surface epithelium (~100 um thick)

55
Q

how often are surface lining cells renewed?

A

every 3-5 days

56
Q

mucous neck cells location

A

neck of gastric glands

57
Q

can mucous neck cells divide?

A

maybe

58
Q

mucous neck cell description

A
  • short microvilli
  • apical mucous granules
  • prominent golgi
  • shorter columnar cell than surface lining cells
59
Q

what do mucous neck cells secrete?

A

soluble mucous - not as thick as mucus produced by surface lining cells

60
Q

what induces mucous neck cell secretion?

A

vagal stimulation

61
Q

parietal/oxyntic cells description

A
  • pyramidal-shaped cells in upper half of gastric glands
  • eosinophilic w/ H&E
  • intracellular tubulovesicular system
  • many mitochondria
  • secretory intracellular canaliculi
62
Q

function of parietal/oxyntic cells

A

seecrete HCl and gastric intrinsic factor

63
Q

what is gastric intrinsic factor and why is it needed?

A

glycoprotein needed for vitamin B12 absorption in small intestine

64
Q

intracellular canaliculi of parietal cells

A

deep invaginations of the apical plasma membrane lined by microvilli

65
Q

changes to parietal cell when stimulated to secrete HCl

A
  • number of microvilli increase

- complexity of the tubulovesicular system decreases

66
Q

what stimulates HCl secretion?

A

ACh and gastrin (APUD cells of pylorus)

67
Q

how is HCl formed by parietal cells?

A

H+, K+, and Cl- are pumped into canaliculus and then HCl is formed extracellularly

68
Q

what event increases effects of ACh and gastrin on parietal cell secretion?

A

histamine binding to histamine H2 receptor

69
Q

what cells produce histamine?

A

enterochromaffin-like cells in lamina propria around gastric glands

70
Q

what drugs inhibit histamine-dependent acid secretion?

A

anti-acid drugs like cimetidine (1st generation)

71
Q

what drugs inactivate acid secretion?

A

2nd generation drugs - omeprazole - bind to H+, K+-dependent ATPase

72
Q

describe series of reactions mediated by CA that affects blood and mucous pH on surface

A
  • CO2 absorbed from blood or formed in parietal cells (metabolism) combines w/ OH- to form carbonic acid (requires CA)
  • carbonic acid -> HCO3- and H+
  • HCO3- diffuses out of cell and is picked up by capillaries
73
Q

what happens to the HCO3- once it exits the parietal cells?

A

enters a fenestrated capillary in lamina propria, w/ blood flowing toward surface epithelium -> diffuses into the mucus blanket to increase the pH

74
Q

chief/zymogenic cells

A
  • pyramidal-shaped cells in lower half of fundic glands

- basophilic w/ H&E

75
Q

what do chief/zymogenic cells secrete?

A
  • pepsinogen

- rennin and lipase precursors

76
Q

pepsinogen

A

precursor of pepsin enzyme

77
Q

chief/zymogenic cell description

A
  • abundant basally located rER
  • supranuclear golgi
  • apical secretory granules (zymogen)
78
Q

enteroendocrine cells

A
  • DNES = diffuse neuroendocrine cells

- also called APUD cells = amine precursor uptake and decarboxylation cells

79
Q

do all enteroendocrine cells take up amine precursors?

A

no

80
Q

number of enteroendocrine cell types

A

> 12 different cell types that contain small hormone-containing granules

81
Q

how many hormones does any given enteroendocrine cell secrete?

A

only one hormone

82
Q

where are enteroendocrine cells located?

A

down near base of crypts

83
Q

what is typical of all cells of the diffuse endocrine system?

A

numerous small, electron dense granules

84
Q

gastric juices

A
  • water
  • HCl
  • mucus
  • pepsin
  • lipase
  • rennin
  • electrolytes
85
Q

what facilitates activation of pepsinogen to pepsin?

A

very acidic conditions (pH 2.0) - catalyzes partial hydrolysis of proteins

86
Q

regulation of gastric secretion, in general

A

affected by neural (vagus n.) and hormonal activity

87
Q

secretin

A
  • released by cells in duodenum when pH < 4.5
  • stimulates pancreatic HCO3- and fluid section
  • stimulates chief cells to secrete pepsinogen
88
Q

gastrin

A
  • G cells in pylorus and duodenal mucosa
  • 2 forms: small G17 in pylorus + large G34 in duodenum
  • stimulates HCl secretion
89
Q

somatostatin

A
  • D cells of pylorus and duodenum
  • inhibits gastrin release
  • indirectly inhibits HCl secretion
90
Q

gastric inhibitory peptide/ urogastrone

A
  • cells in duodenum and jejunum
  • directly inhibit HCl secretion
  • stimulate insulin release
91
Q

what are the two gastric hormones?

A

cholescystekinin (CCK) and motilin

92
Q

cholescystekinin

A
  • produced in duodenum and jejunum

- stimulates gallbladder contraction when fat is in small intestine

93
Q

motilin

A

-released cyclically (every 90 min) during fasting from cells in upper GI tract

94
Q

gastritis

A

gastric mucosal inflammation common in middle-aged and older individuals - may be superficial or affect entire thickness, causing mucosal atrophy

95
Q

what causes gastritis

A

often unknown etiology

96
Q

zollinger-ellison syndrome

A

patients w/ gastrin secreting tumors have hyperplasia and hypertrophy of fundus + high acid secretion -> stomach ulcers, diarrhea

97
Q

gastric/peptic ulcers

A

areas of gastric or duodenal mucosa destroyed by gastric secretions

98
Q

where are gastric/peptic ulcers commonly found?

A

in cardiac and pyloric regions and first part of duodenum

99
Q

causes of gastric/peptic ulcers

A
  • excess HCl secretion
  • nervous irritation
  • reduced vascular supply
  • reduced mucus secretion
  • infection (H. pylori)
  • NSAIDS
100
Q

treatment of gastric/peptic ulcers

A
  • antibiotics
  • stress management
  • elimination of alcohol, aspirin/NSAIDS, and cigarette use
  • antacids and/or drugs that inhibit gastric secretions
101
Q

how do NSAIDS cause ulcers?

A

shut down prostaglandin synthesis, which is important in protecting the GI tract

102
Q

phases of H. pylori infection

A
  • active phase
  • stationary phase
  • colonization phase
103
Q

active phase of H. pylori infection

A

H. pylori increases gastric pH by producing ammonia via urease

104
Q

stationary phase of H. pylori infection

A

bacteria attach to fucose containing receptors on surface of mucus cells in pylorus - bacteria releases proteases that kill surface cells

105
Q

colonization phase of H. pylori infection

A

bacteria detach and replicate in mucus blanket

Histology - Exam 3 (12 decks)

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