GI System Histology Flashcards

1
Q

What are the layers of the mucosa in the GI tract?

A
  1. Epithelium
  2. Lamina propria - connective tissue, small blood vessels and lymphatics
  3. Muscularis mucosa (smooth muscle)
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2
Q

What are the three principal functions of the GI mucosal layer?

A
  • Secretion – provides lubrication, digestive enzymes, acidic and and alkaline fluids, and bile into the lumen of the GI tract
  • Absorption – small molecules of food, water, electrolytes, vitamins, and recyclable products such as bile components and cholesterol into the blood and lymph of lamina propria
  • Protection - serves as a barrier to noxious substances, antigens, and pathogenic organisms
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3
Q

What are the principal functions of the submucosa of the GI tract?

A

provide blood and lymph vessels, nerve plexus, and occasional glands

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4
Q

What are the principal functions of the inner circular layer of the muscularis externa of the GI tract?

A

compress and mix contents in the lumen

NOTE: Inner circular forms sphincters at specific locations along digestive tract!

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5
Q

What are the principal functions of the outer longitudinal layer of the muscularis externa of the GI tract?

A

propels the contents by shortening the tube

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6
Q

The muscularis externa of the GI tract is controlled by what?

A

enteric nervous system

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7
Q

What does the mucosa of the esophagus consist of?

A

1) SS nonkeratinized epithelium
2) Thin lamina propria with cardiac glands (mucous) at upper and lower ends
3) GALT
4) esophageal glands

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8
Q

What does the submucosa of the esophagus consist of?

A

mucus-secreting tubuloalveolar glands called esophageal glands proper

mucus provides protection to the mucosa layer

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9
Q

What can be found between the inner circular and outer longitudinal fibers of the Muscularis externa in the esophagus?

A

Auerbach’s plexus

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10
Q

The esophagus can be divided into three regions. What are these divisions based on?

A

the amount of skeletal and smooth muscle in the muscularis externa

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11
Q

What is the muscle composition of the upper third of the esophagus?

A

all skeletal

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12
Q

What is the muscle composition of the middle third of the esophagus?

A

mixture of skeletal and smooth

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13
Q

What is the muscle composition of the lower third of the esophagus?

A

all smooth

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14
Q

Skeletal to smooth muscle transition enables what?

A

voluntary control to involuntary control of swallowing

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15
Q

What layer of the muscularis externa form upper and lower esophageal sphincters?

A

inner circular

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16
Q

Incompetent inferior esophageal sphincter may cause what?

A

1) chronic heartburn and erosion of the mucosa or,

2) gastroesophageal reflux disease (GERD)

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17
Q

What is the major function of the stomach and how does it accomplish this?

A

digestion. It does this by adding acidic fluid and mixing digested content into a chyme

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18
Q

What are the layers of the mucosa of the stomach?

A

1) epithelium
2) lamina propria
3) muscularis mucosa (typically)

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19
Q

What is the epithelium of the stomach made of?

A

simple columnar

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20
Q

What does the lamina propria of the stomach contain?

A

CT, gastric glands, and lymphatic cells

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21
Q

What are rugae?

A

large longitudinal gastric folds in the stomach (which disappear when the stomach is distended)

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22
Q

What layer of the stomach forms the core of rugae?

A

submucosa

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23
Q

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

A

3 layers- an inner oblique, middle circular, and outer longitudinal

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24
Q

The plyoro-duodenal sphincter is formed from what?

A

the middle circular layer of the muscularis externa

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25
Q

Does the stomach have serosa or adventitia?

A

serosa (present on all stomach surfaces)

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26
Q

What can be seen in the simple columnar epithelial of the stomach?

A

surface mucous cells

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27
Q

What do surface mucous cells produce? Why?

A

alkaline mucous to protect stomach lining from acidic chyme

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28
Q

Invaginations of the stomach epithelium into the lamina propria are called what?

A

gastric pits

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29
Q

What cell types can be found in gastric glands?

A

1) stem cells
2) mucous neck cells
3) chief cells
4) parietal cells
5) enteroendocrine cells

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30
Q

What is the role of chief cells in gastric glands and what part of the gland are they primarily found in?

A

found in the deeper part of gland and secrete pepsinogen

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31
Q

What is the role of parietal cells in gastric glands and what part of the gland are they primarily found in?

A

most numerous in the upper part of the gland. They secrete HCl and intrinsic factor (which facilitates vitamin B12 absorption in the ileum)

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32
Q

What is the role of enteroendocrine cells in gastric glands and what part of the gland are they primarily found in?

A

all levels, secrete a variety of gastric hormones into the lamina propria

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33
Q

Where are stem cells found in gastric glands?

A

only in the isthmus region. Thus, cell division and regeneration is restricted to the isthmus region only.

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34
Q

What is the life span of:

a) surface mucous cells
b) parietal cells
c) enterendocrine cells

A

a) 3-5 days (thus, most new cells from the isthmus migrate up to this region)
b) 6 months
c) 3 months

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35
Q

What is the difference between rugae, mammillated folds, and gastric glands/pits?

A

rugae- contain mucosa and submucosa

mammillated folds- small elevations of mucosa only

gastric glands/pits- are not elevations, small holes

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36
Q

What are gastic ulcers?

A

erosions of stomach mucosa

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37
Q

Helicobacter pylori infection of the stomach causes which gastric ailments?

A

Cause of chronic gastritis, peptic ulcers, gastric carcinoma and gastric lymphoma

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38
Q

What part of the stomach are helicobacter pylori infections most common?

A

infection tend to concentrate in neck of gastric glands lined by mucus-secreting cells including the stem cells

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39
Q

T or F. Chronic injury and inflammation of
the neck region (site of proliferating gastric cells) caused by Helicobacter pylori gland infection is likely to accelerate proliferation of cells in gastric carcinoma in neck of the gastric
gland

A

T.

40
Q

What is the main function of the small intestine?

A
  • Absorption of nutrients is major function

- Completion of digestion

41
Q

What modifications does the intestinal wall exhibit to increase surface area for absorption?

A
  1. plicae circulares (aka valves of Kerchring)- permanent transverse folds of the mucosa, increase surface area 3-fold
  2. villi- finger-like projections of the mucosa – increase surface area 10-fold+
  3. microvilli- on the surface of epithelial cells, form a striated (brush) border, increase surface area 100-fold+
42
Q

Where are plicae circulares most common?

A

the jejunum

43
Q

What is the core of plicae circulares composed of?

A

submucosa

44
Q

The surface epithelium of intestinal villi has indentations that lead to glands named what?

A

Intestinal crypts or crypts of Lieberkuhn

45
Q

What is Celiac disease?

A

People with celiac disease cannot tolerate gluten, a protein in wheat, rye, and barley. Gluten triggers immune system to damage or destroy villi.

46
Q

Microvilli have a core made of what?

A

actin that allows for contraction/spreading of the microvilli

47
Q

What is the epithelium in the small intestine?

A

simple columnar

48
Q

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

A

1) enterocytes
2) goblet cells
3) Paneth cells
4) M cells
5) enteroendocrine cells
6) intermediate cells (stem cells)

49
Q

What is the role of enterocytes in the small intestine?

A
  • the primary absorptive cell, found on the villi, the general surface and in the glands
  • are attached to neighboring cells by tight junctions
  • in the glands, the enterocytes also secrete water and electrolytes
50
Q

Where are goblet cells found in the epithelium in the small intestine?

What do they contain?

A
  • found on villi and in glands

- apical part of cell contains mucinogen granules

51
Q

What do Paneth cells do?

A
  • Secretes lysozyme that digests bacterial cell walls and other antibacterial substances
  • Can phagocytose certain bacteria and protozoa
  • Paneth play significant role regulating bacteria in intestinal glands
52
Q

What do M cells do in the small intestine?

A

have microfolds rather than microvilli

  • are antigen-presenting cells, overlie lymphatic nodules
  • endocytose microorganisms and macromolecules from intestinal lumen and discharge them into the underlying lymphatic tissue
53
Q

What do enteroendocrine cells do?

A

secrete various peptide hormones

54
Q

What do intermediate cells (stem cells) do?

A
  • comprise most cells in the lower half of the gland
  • intermediate between enterocyte and goblet
  • can divide and form any of the epithelial cells
55
Q

How often are:

a) absorptive and goblet cells renewed
b) paneth cells

A

a) every 5-6 days,

b) about every 4 weeks

56
Q

What are the contents of the lamina propria in the mucosa in the small intestine?

A
  • is heavily infiltrated with lymphoid tissue – GALT.

- Aggregation of lymph nodules, Peyer’s patches, (best developed in the ileum)

57
Q

What is a lacteal?

A

each villus in the lamina propria of the small intestine contains a lymphatic capillary, called a lacteal, for absorption of fat

58
Q

What are the layers of the muscularis mucosa in the small intestine?

A
  • typical: inner circular, outer longitudinal

- fibers extend into the villi to enable movement of villi

59
Q

What are Brunner’s glands (what is their role) and what parts of the small intestine have Brunner’s glands?

What layer of the wall are they found in when present?

A

Duodenum contains Brunner’s glands in submucosa, secretes alkaline to buffer acid from the stomach entering duodenum

NOTE: The jejunum also has very few Brunner’s glands,

60
Q

Which parts of the small intestine has Peyer’s patches?

A

Ileum. Neither the Jejunum or the duodenum have peer’s patches

Peter’s patches are aggregations of lymph nodules

61
Q

Does the small intestine have:

a) a submucosa
b) muscularis externa
c) serosa and avdentitia

A

yes to all three

Muscularis externa has inner circular and outer longitudinal orientation of muscle groups

62
Q

What is the main function of the large intestine?

A

absorption of water and electrolytes and elimination of solid wastes and undigested food

63
Q

What are the Teniae coli of the large intestine formed from?

A

three bands, created from the outer longitudinal layer of muscularis externa

64
Q

What is the epithelium of the large intestine?

A

simple columnar

65
Q

What kinds of cells does the epithelium of the large intestine contain?

A

same cell types as small intestine, except more goblet cells, no Paneth cells

66
Q

Is the GALT well developed in the lamina propria of the large intestine?

A

yes.

NOTE: there are no lymphatic vessels (hence slow metastasis of colon cancers)*

67
Q

What are some main features of the appendix?

A
  • has no teniae coli
  • characterized by many lymph nodules in the propria, so large they encroach on the submucosa
  • usually, much debris seen in the lumen
68
Q

What 3 structures are named the portal triad.?

A

the proper hepatic artery, the common bile duct, and the portal vein

69
Q

What is a portal vein?

A

a vessel that carries blood between two capillary beds.

Portal vein to the liver carries blood between capillaries of organs in the abdomen to sinusoids in the liver.

70
Q

Is blood oxygenated in the portal vein or the proper hepatic artery?

A

the proper hepatic artery

71
Q

What does a portal canal contain?

A

portal triad, lymphatic vessels, nerves, and CT

72
Q

Where is blood from portal vein and hepatic arteries combined?

A

in sinusoids, which then flows into a venule, the central vein, which then flow to a sub lobular vein, and finally to the hepatic veins which empty into the IVC

73
Q

What make up approximately 80% of cells in liver?

A

hepatocytes

74
Q

What is the composition of hepatocytes?

A

Many are binucleated with large amount of heterchromatin, rER, sER, and Golgi units

make proteins, involved in storage, metabolism, and waste removal

they can regenerate

75
Q

What is the role of Ito (stellate) cells in the liver?

A

stores vitamin A

76
Q

What are the name of the macrophages responsible for removing bacteria and damaged red blood cells from blood?

A

Kupffer cells (they are located in the sinusoids)

77
Q

What are sinusoids are lined with?

A

a thin fenestrated endothelium

78
Q

Where is the perisinusoidal space (aka space of Disse) located in the liver?

A

between the fenestrated endothelium of sinusoids and hepatocytes

79
Q

What is Bile produced by?

A

hepatocytes

80
Q

What is the biliary pathway?

A
Canaliculi
Canal of Hering
Interlobular bile ducts
R or L Hepatic Duct
Common Hepatic Duct
Common Bile Duct
81
Q

What components of bile are taken in to the intestine for reabsorption?

A
  • Phospholipids (lecithin is an example) and cholesterol are metabolic substrates for other cells in the body.
  • Bile salts (aka bile acids) act as emulsifying agents that aid in digestion and absorption of lipids from the gut and help to keep the cholesterol and phospholipids of the bile in solution.
  • Electrolytes: Na+, K+, Ca2+, Cl-, HCO3-
82
Q

What components of bile are taken in to the intestine for disposal?

A

Bile pigments, the end product of hemoglobin degradation from bilirubin.

83
Q

What are the main functions of the gallbladder?

A
  • Concentrates the bile and stores it during fasting.
  • Secretion is stimulated by hormones from the small intestines.

Discharges bile into the cystic duct, then common bile duct, which carries it to the duodenum.

84
Q

What is unique about the mucosa layer of the gallbladder?

A

has simple columnar epithelium but lacks a muscularis mucosae in mucosae layer

NOTE: Wall also lacks a submucosa

85
Q

T or F. Muscularis externa of the gallbladder is

irregularly arranged

A

T

86
Q

How does the gallbladder concentrate bile?

A

achieved by removal of H2O.
• An osmotic gradient draws water from the lumen into the intercellular space between adjacent cells.

• Hydrostatic pressure forces water into lamina propria, and then into capillaries & venules.

87
Q

What are gallstones and what are the types?

A
  • Form when bile in the
    gallbladder hardens into pieces of
    stone-like material.
  • Two types: cholesterol and
    pigment stones
88
Q

Is the pancreas an exocrine or an

endocrine gland?

A

Both

89
Q

What does the exocrine component of the pancreas do?

A

synthesizes and secretes enzymes and bicarbonate into ducts.

90
Q

What does the endocrine component of the pancreas do?

A

synthesizes and secretes the hormones (insulin, glucagon, and the peptide, somatostatin) into the blood.

91
Q

Where is the exocrine compartment of the pancreas located?

A

in the acinar pancreas

92
Q

Where is the endocrine compartment of the pancreas located?

A

located in the islets of Langerhans

93
Q

Describe the organization of the exocrine component of the pancreas

A

Structurally organized into acini (alveoli) - have serous cells.

Acini cells have zymogen granules, which are inactive digestive enzymes:
• proteolytic,amylolytic, lipases, and nucleolytic enzymes.
• Acini cells secrete into the duct system for transport to the intestines, where enzymes become active.

94
Q

Describe the organization of the duct system of the exocrine component of the pancreas

A

• Pancreas acini secrete about 1 L/day.

• Within acini, centroacinar cells initiate intercalated ducts
– add water and bicarbonate to secretion

• The hierarchy of ducts is intercalated > intralobular > interlobular > main pancreatic duct!

95
Q

What are intercalated ducts made of?

A

squamous cells

96
Q

What are intralobular ducts made of?

A

Cuboidal or low columnar cells

97
Q

What are interlobular ducts made of?

A

low columnar, lots of CT, located between lobules