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Term 2: Histology > Gut Hose > Flashcards

Gut Hose Flashcards

1
Q

What are the four main layers of the gut wall?

A
  • mucosa
  • submucosa
  • muscularis externa
  • serosa/adventitia
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2
Q

What layers are contained within the mucosa?

A
  • epithelium
  • lamina propria
  • muscularis mucosae
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3
Q

(T/F) Muscularis mucosa is unique to the GI tract.

A

T

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4
Q

What is the function of the muscularis mucosa?

A
  • contains a thin layer of smooth muscle

- mediates local movements of the mucosa

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5
Q

What is the major role of the mucosa in the GI tract?

A

-absorption of nutrients

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6
Q

What is contained within the submucosa?

A
  • denser connective tissue (than lamina propria)
  • blood vessels
  • Lymphatics/immune cells
  • glands (duodenum and esophagus)
  • submucosal/meissner’s nerve plexus
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7
Q

Where is meissner’s nerve plexus located?

A

-the submucosa

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8
Q

What is the muscularis externa composed of?

A
  • smooth muscle
  • connective tissue between layers
  • has an inner circular and an outer longitudinal component
  • myenteric/auerbach nerve plexus
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9
Q

Where is the myenteric/auerbach nerve plexus located?

A

-connective tissue of the muscularis externa

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10
Q

What is the function of the muscularis externa?

A

-mixes and propels luminal contents along the GI tract

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11
Q

What is contained within the serosa/adventitia?

A
  • loose connective tissue
  • blood and lymphatic tissues
  • adipose tissue
  • simple sqamous covering called the mesothelium
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12
Q

What is the mesothelium?

A

-a simple squamous covering around the serosa/adventitia

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13
Q

How often do cells in the epithelium of the small intestine turn over?

A

every 3-5 days

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14
Q

What are the two portions of GI epithelium? Which portion do stem cells tend to live in?

A
  • Villus
  • Crypt

-Stem cells live in crypt

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15
Q

When does secondary peristalsis occur?

A

when food gets stuck, the tube neetds continuous peristalsis to unstick it

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16
Q

What is retroperistalsis?

A

throwing up

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17
Q

What is receptive relaxation of the stomach?

A

-the relaxation of smooth muscle layers to allow food to expand the stomach

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18
Q

What is pyloric grind?

A

When the pyloric sphincter contracts and circulates the food around the stomach.

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19
Q

What is the migrating motor complex (MMC)?

A
  • a sweeping that travels through the stomach and intestine which clears anything out that was left over from digestion
  • occurs every 90 minutes
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20
Q

What are the two movements of the stomach that involve movement of the epithelium?

A
  • Mucosal squeeze: Up and down motion

- Mucosal Flutter: horizontal wave-like motion that coccurs in the muscularis mucosa to aid the stomach in digestion

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21
Q

What is segmentation?

A

Local mixing in the small intestine and large intestine

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22
Q

What is segmentation called in the colon? Why?

A
  • haustration

- Called this because there is consolidation of fecal matter

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23
Q

What occurs in the large intestine insteadof MMC?

A

-mass movements, which consolidate things into poop

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24
Q

Why doesn’t mucosal flutter occur in the large intestine?

A

-because of the big bolus of poop, it wouldn’t accomplish much

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25
Q

What is the vagovagal reflex?

A
  • response to an expansion of the stomach

- tells us to poop

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26
Q

What cells are the pacemaker of the gut, and where are they located?

A
  • interstitial cells of Cajal

- A part of the myenteric plexus of the enteric nervous system

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27
Q

What type of epithelium is present in the esophagus?

A

-non-keratinized stratified squamous epithelium

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28
Q

Why is the lamina propria of the esophagus interdigitated with down growths of epithelium?

A

-to prevent food we swallow from scraping off our epithelium

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29
Q

Why does the epithelium of our esophagus have melanocytes?

A
  • thought to have more of a free-radical detox role

- can still get melanoma here

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30
Q

Why isn’t there a very pronounced muscluaris mucosa in the esophagus?

A

-food doesn’t spend much time in the esophagus for digestion

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31
Q

What do esophageal cardiac glands do and where are they present?

A
  • near the transition of the esophagus and the stomach

- it produces mucous which helps prevent stomach acid from damaging the esophagus near the stomach

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32
Q

Describe the muscle types found in the muscularis externa of the esophagus.

A
  • upper 1/3 is skeletal
  • middle 1/3 is mixed skeletal and smooth
  • -lower 1/3 is smooth
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33
Q

Which nerve plexus is responsible for pirmary, secondary, and reverse peristalsis in the esophagus?

A

-myenteric plexus

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34
Q

Does the esophagus have serosa or adventitia?

A
  • both
  • most is adventita
  • distal 1-2cm has serosa
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35
Q

What is the function of the upper esophageal sphincter?

A
  • prevents air form entering into the esophagus during breathing
  • prevents reflux of esophageal contents into the pharynx
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36
Q

What is the function of the lower esophageal sphincter?

A

-protects the esophagus from gastric contents

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37
Q

Are the upper and lower esophageal sphincters made of smooth or skeletal muscle?

A
  • upper: skeletal (not voluntary)

- Lower: smooth

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38
Q

What is the gastroesophageal junction, and what signifies its presence histologically?

A
  • it is the transition point between the esophagus and the stomach
  • the epithelium changes from squamous to columnar at the Z-line
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39
Q

What is esophageal Varices?

A
  • dilation of veins from the deep submucosa when the liver is failing
  • usually caused by portal hypertension
  • Veins can rupture and bleed into esophagus
  • means your liver is fucked
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40
Q

What is GERD?

A
  • gastro esophageal reflux disease

- abnormal relaxation of the lower esophageal sphincter allows stomach acid to come up from the stomach

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41
Q

What is Barrett’s Esophagus?

A
  • occurs after chronic exposure of the esophageal epithelium to shomach acid
  • involves a histological change in the epithelium so that it looks like the stomach or small intestine
  • metabplasia of squamous epithelium to simple columnar increases the risk of a cancer called esophageal adenocarcinoma
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42
Q

What are the overall functions of the stomach?

A
  • stretch to accommodate food bolus
  • perform mechanical digestion
  • perform chemical digestion
43
Q

What are rugae?

A
  • large longitudinally directed folds of mucosa and submucosa
  • take part in receptive relaxation
44
Q

Does the stomach have a serosa or an adventitia? What is it made up of? What is its function?

A
  • serosa
  • connective tissue, blood vessels, mesothelium
  • it protects the stomach from friction as it expands to mix and propel food
45
Q

What are the three layers of muscularis externa in the stomach?

A
  • outer longitudinal
  • middle circular
  • inner oblique
46
Q

What defines the pyloric sphincter histologically?

A

-a thickening of the middle circular layer of the muscularis externa

47
Q

What makes up the submucosa of the stomach?

A
  • connective tissue
  • LARGE blood and lymphatic vessels
  • diffuse lymphoid cells (macrophages and mast cells)
48
Q

What type of epithelium is present in the stomach?

A

-simple columnar

49
Q

What cell types are present in the epithelium of the stomach?

A
  • surface mucous cells

- RARELY you’ll find an intraepithelial T lymphocyte, but its not really considered part of the epithelium

50
Q

What are the three portions of gastric glands?

A
  • Gastric pit
  • Isthmus
  • branched tubular gastric glands
51
Q

What are the two major types of cells in the cardial and pyloric gastric glands?

A
  • mucous cells

- enteroendocrine cells

52
Q

What are the 5 major types of cells in the body and fundus gastric glands?

A
  1. Mucous Neck cells
  2. Parietal Cells
  3. Chief Cells
  4. Enteroendocrine cells
  5. Stem Cells
53
Q

What do surface mucous cells do?

A
  • they line the stomach lumen and secrete a thick adherent viscous mucous layer
  • this mucous is rich in bicarb which protects the stomach from the low pH of the lumen
54
Q

What do mucous neck cells do?

A
  • line the neck/isthmus of gastric glands.

- They produce mucous here that is less alkaline than that of the surface mucous cells

55
Q

What is mucous made of?

A

-mostly the glycoprotein mucin

56
Q

what type of secretion is mucous secreted by?

A

-merocrine

57
Q

What do parietal (oxyntic) cells do?

A
  • the are located among the mucous neck cells and deeper in the gland
  • they produce HCL
  • also secrete intrinsic factor, which binds B12
58
Q

What stimulates the secretion of HCl by parietal cells?

A
  • parasympathetic innervation

- histamine and gastrin from the DNES

59
Q

What do Chief (zymogenic) cells do?

A
  • located in lower region of gastric glands

- secrete proteins including pepsinogens and gastric lipases

60
Q

Where are enteroendocrine cells located in the stomach?

A

they are scattered around the gastric mucosa

61
Q

What can cause stomach ulcers?

A
  • reacting of acid and pepsin with epithelium
  • H. Pylori is a bacteria known to cause ulcers
  • NSAIDs
  • Steroids
  • Stress
62
Q

What type of epithelium is in the small intestine?

A

-cytokeratin positive simple columnar

63
Q

What 5 cell types are present in the small intestine epithelium?

A
  • enterocytes
  • goblet cells
  • paneth cells
  • enteroendocrine cells
  • stem cells
64
Q

What is the epithelium of the small intestine organized into?

A

-Villi and crypts

65
Q

What is contained within the lamina propria of the small intestine?

A
  • fibroblasts and loose connective tissue
  • continuous fenestrated capillaries with diaphragms
  • meissner’s plexus
  • lymphatics and immune cells, producing IgA, G and M
66
Q

What makes up the brush border of the small intestine?

A

-microvilli and glycocalyx

67
Q

On which cells in the small intestine is the brush border located?

A

-enterocytes

68
Q

Which part of the small intestine has the highest density of enterocytes?

A

-the duodenum

69
Q

What do enterocytes do?

A
  • they are absorptive columnar cells

- produce disaccaridases and peptidases

70
Q

What is the function of small intestine goblet cells?

A

-secrete glycoproteins to form mucous, which protects the GI lining and lubricates chyme

71
Q

What do paneth cells do? Where do they live?

A
  • part of the innate immune system
  • secrete lysozymes, phopholipase A, and defensins
  • protects stem cells

-live at the base of intestinal crypts

72
Q

What do enteroendocrine cells of the small intestine do?

A
  • control motility and secretion of enzymes

- control our sense of satiety

73
Q

Where are stem cells of the small intestine located?

A

-the bottom of the intestinal crypts

74
Q

What is the turnover rate of the epithelium of the villi in the small intestine?

A

-3-5 days

75
Q

What is the turnover rate of the crypts in the small intestine?

A

30 days to 1 year

76
Q

What is mucositis-ulceration and what can cause it?

A
  • an influx of inflammatory cells to the lamina propria, with a loss of epithelial cell and mucosal structure
  • disrupts large areas of the epithelial lining of the small intestine

-side effect of chemotherapy

77
Q

What is adenocarcinoma?

A

-the most common type of small intestine cancer, though still extremely rare

78
Q

What are enteric pathogens?

A

-any microbe that is able to cause enteric disease

79
Q

What are plicae circularis and where are they located?

A
  • submucosa that is thrown into circular/semilunar folds to increase surface area
  • located in the submucosa of the small intestine
80
Q

What are the two shapes of the plicae circularis, and where are they respectively found?

A
  • leaf in duodenum

- finger in ileum

81
Q

What lies between the inner circular and outer longitudinal layer of smooth muscle in the small intestine?

A

-myenteric (auerbach) nerve plexus

82
Q

What are Brunner’s Glands and where are they located?

A
  • branched tubular glands that produce a mucous product that is very alkaline
  • they are located in the mucosa and submucosa of the proximal duodenum
83
Q

What are peyer’s patches and where are they located?

A
  • they are a part of the GALT, specifically the lymphoid nodules
  • contain M cells (not motillin) which are specialized epithelial cells that have a porous basement membrane with pockets that contain lymphocytes and dendritic cells.

-located in the small intestinal mucosa of the ileum

84
Q

What are the three layers of the mucosal barrier of the small intestine?

A
  • mucous
  • epithelium
  • GALT
85
Q

What is the histological finding in celiac disease?

A
  • accumulation of T and Plama cells in the lamina propria of the small intestine
  • whats left of the enterocytes have fat globules inside, and a stratified nucleus, with no brush border and an increase in crypt mitotic cells
86
Q

What cells are contained within the epithelium of the large intestine?

A
  • Goblet cells
  • Colonocytes
  • DNES cells
  • stem cells
  • Lymphocytes
87
Q

What do colonocytes do?

A
  • absorptive columnar cells

- absorb water

88
Q

Describe the intestinal glands of the large intestine.

A
  • tubular glands in epithelium that extend into the lamina propria
  • Lined by goblet cells and colonocytes
  • thin brush border
  • stem cells in bottom 1/3 of gland
89
Q

Describe the muscularis mucosa of the large intestine.

A

-has distinct inner circular and outer longitudinal layers

90
Q

How is the outer longitudinal layer of the muscularis externa different in the large intestine?

A

-it is present as 3 equally spaced bands of smooth muscle called Teniae Coli.

91
Q

What are omental appendages?

A
  • suspended masses of adipose tissue on the large intestine
  • small and pendulous
  • protrude from the serosal surface
92
Q

What compromises the distal end of the large intestine?

A
  • rectum
  • rectoanal junction
  • anal canal
  • anus
93
Q

What type of epithelium does the Rectum have vs the anal canal?

A
  • rectum is simple columnar

- anal canal is stratified squamous epithelium

94
Q

Where are anal columns present?

A

the anal canal

95
Q

What are anal columns?

A
  • longitudinal folds of mucosa and submucosa located in anal canal
  • contain a rectal venous plexus
96
Q

What is the pectinate line?

A

-the transition from the simple columnar epithelium of the rectum to the stratified squamous epithelium of the anal canal

97
Q

What is the appendix composed of?

A
  • inner and outer muscularis externa
  • filled with lymphoid tissue
  • houses normal bacterial flora
98
Q

What is Hirshsprungs disease?

A
  • caused by heterogeneous defects in migration and survival of neuroblasts. Leads to an altered distribution of interstitial cells of cajal
  • complications include distention of proximal colon with muscular wall hypertrophy/rupture
99
Q

Which contains villi, the small intestine or the large intestine?

A

-only small

100
Q

Are there paneth cells in the large intestine?

A

-no

101
Q

What is the relative lengths of the crypt of glands in the small intestine vs large intestine?

A

-small intestine has shorter crypts than large intestine

102
Q

How is the lymphoid tissue of the submucosa organized in the small intestine compared to the large intestine?

A

Small intestine:
-organized peyer’s patches

Large Intestine:
-diffuse lymphoid nodules

103
Q

Compare/contrast the microvilli and glycocalyx in the small and large intestine.

A

Small intestine:
-extensive microvilli and glycocalyx

Large Intestine:
-patchy microvilli and no glycocalyx

Term 2: Histology (6 decks)

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