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GI Week 1 > Lecture 3: HIstology of the Esophagus, Stomach, Small intestine and Colon > Flashcards

Lecture 3: HIstology of the Esophagus, Stomach, Small intestine and Colon Flashcards

1
Q

What is the general architecture of hollow visceral organs?

A 
From lumen to the capillaries
1. surface epitheium
2. lamina propria
3. muscularis mucosae (smooth muscle)
4. Submucosa
5. Inner circular muscle layer (smooth)
6. Outer longitudinal muscle layer (smooth)
7. Adventitia 
IF NO ADVENTITIA
8. Serosal layer
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2
Q

Where are the nerves located?

A
  1. submucosal nerve plexus (meissners)

2. Myenteric plexus (nerves in between the inner circular muscle layer and outer longitudinal muscle layer (auerbachs)

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3
Q

What makes up the “mucosa” of a GI tube structure?

A

The combination of

i. surface epithelium
ii. lamina propria
iii. muscularis mucosae

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4
Q

What are desmosomes?

A

Molecular complexes of cell adhesion proteins and linking proteins that attach the cell surface adhesion proteins to intracellular keratin cytoskeletal filaments

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5
Q

What are the characteristics of tight junctions?

A

Network of sealing protein fibers of transmembrane proteins embedded in both plasma membranes, with extracellular domains joining one another directly

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6
Q

What are the key characteristics of gap junctions?

A

Directly connects CYTOPLASM of two cells through hydrophilic channels, which allows various MOLECULES and IONS to pass freely between cells

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7
Q

What is the epithelium in the esophagus?

A

Squamous (stratified non keratinized squamous epithelium)

No absorption and no secretion

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8
Q

What is the Latin word for grapes?

A

Acini

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9
Q

What can be seen in the esophagus?

A

Acini below the muscle layers

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10
Q

What is the gastric environment?

A
  1. exposure of food to acid
  2. No significant absorption in stomach
    Secretion = needs glands
    Epithelium = glandular
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11
Q

What type of epithelium is typical of stomach?

A

Glandular

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12
Q

What is the cardiac type mucosa of stomach?

A

The transition from esophagus to stomach
Z line
Metaplasia
Squamous to gastric oxyntic mucosa

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13
Q

What are oxyntic glands?

A

Glands forming or secreting acid

Parietal cells of gastric glands

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14
Q

What are the three glandular regions of stomach and what are their functions?

A
  1. cardia
    -area of reactive changes
  2. Corpus
    -oxyntic mucosa (acid producing
  3. Antrum
    -mucous glands predominate
    NO OXYNTIC glands
    Gastrin producing endocrine cells
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15
Q

What are the gastric pits?

A

The pits that contain glandular cells of the stomach

Parietal and chief cells

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16
Q

What produces acid production? Where?

A 
Produced in CORPUS of the stomach
Parietal cells (“P” for pH)
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17
Q

What do parietal cells do?

A

Stimulated to produce acid by

i. histamine
ii. gastrin
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18
Q

What does gastrin do?

A

Acts on parietal cells
Stimulates enterochromaffin like cells in the corpus
Enterochromaffin cells make histamine
Secreted by ANTRAL neuroendocrine cells into the blood stream

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19
Q

What do enterochromaffin-LIKE cells do?

A

Make histamine

Stimulated by gastrin

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20
Q

What happens if you see a shitload of inflammatory cells in lamina propria of stomach?

A

Abnormal

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21
Q

What happens if you lack parietal cells?

A

Autonomous proliferation of neuroendocrine cells in the gastric fundus

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22
Q

What happens if you immunologically destroy parietal cells?

A

Leads to hyperacidity

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23
Q

What are the histological features of the parietal cells?

A

HCl producing parietal cells are PINK

So P for pink for pH

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24
Q

What are the histological features of the chief cells?

A

Blue cells

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25
Q

Where do the enterochromaffin-LIKE cells reside?

A

In between parietal and chief cells

26
Q

What do chief cells do?

A

Releases the following

i. pepsinogen
ii. gastric lipase
iii. rennin
27
Q

What does pepsinogen do?

A

Works in conjunction with parietal cell

Gastric acid converts pepsinogen to pepsin

28
Q

What is pepsin?

A

An enzyme that degrades food proteins into peptides

29
Q

What is the histological summary of the corpus?

A
  1. rugae
  2. gastric pits
  3. pits are lined by FOVEOLAR epithelium
  4. beneath the pits lie large amounts of secretory cells including
    i. parietal cells
    ii. chief cells
    iii. neuroendocrine cells
30
Q

What are the histological features of the cardia?

A

Transition point

So you see gastric pits as well as squamous epithelium

31
Q

What are the key characteristics of the gastric antrum?

A
  1. Foveolae
  2. Antral glands
  3. Acid and enzyme
    Producing glands
    Disappear
  4. Mostly MUCUS
    Secreting glands
  5. also gastrin
    Producing
    Neuroendocrine cells
    Present
32
Q

How is gastrin delivered to parietal and enterochromaffin cells?

A

Through the blood stream
Gastrin stimulates both acid and histamine production
No direct transport from antrum to corpus

33
Q

What is the muscularis propria?

A

Name that is put in front of the circular and longitudinal types of muscle around the visceral gut tubes

34
Q

Why are there B and T cells in the small intestine?

A

Because body is now subjected to inflammatory material

35
Q

What are the two things lining the small intestine?

A
  1. villi (epithelium outside)

2. crypts (epithelium inside)

36
Q

What are the functions of the microvilli?

A
  1. absorption
  2. secretion
  3. cellular adhesion
  4. mechanotransduction
37
Q

What increases the surface area of small intestine?

A
  1. formation of villi
  2. formation of crypts
  3. formation of microvilli
38
Q

What organ secretes the DIGESTIVE enzymes?

A

The pancreas

i. lipase
ii. carbohydrase
iii. protease
iv. Nuclease
39
Q

What are the four types of absorption?

A
  1. passive diffusion
    • lipid soluble objects diffuse most rapidly
  2. Facilitated passive diffusion
    • used for glucose (non lipid soluble shit)
  3. Active transport
    • ions, vitamins, sugar and amino acids
  4. Pinocytosis
    • fluid or particles are engulfed by a cell
    • cell membrane invaginates and encloses fluid or particles then fuses again
    • protein absorption
40
Q

Where are the lymph vessels present in the large intestine?

A

Present in the LAMINA PROPRIA of the small intestin

41
Q

What are paneth cells?

A

Located in the small intestine
Provides phagocytosis and intracellular digestion of intestinal microorganisms
Mostly in the crypts

42
Q

What are Brunner glands? Where are the located?

A

Located in the SUBMUCOSA
In the DUODENUM only
Function:
i. protection from gastric acid (secretes alkaline mucus that contains BICARBONATE)
ii. alkalization to allow digestive enzymes to work

43
Q

What is the significance of bicarbonate?

A

Neutralizes acid of stomach in duodenum

Secreted by Brunner glands in the submucosa

44
Q

What are the different cell types we need to pay attention to in the small intestine?

A
  1. Peyer’s patches
  2. Brunner glands (produces bicarb in duodenum)
  3. Paneth cells (macrophage like)
45
Q

What does the appendix look like?

A

Mucosa with crypts (no villi)
Same general architecture of the entire GI tube
Lymphoid aggregates!
But colon can have lymphoid aggregates too

46
Q

What is the function of the colon?

A
  1. Absorption
    • water
    • sodium
    • chloride
  2. Secretion
    • bicarbonate
    • mucus
    • Goblet cells secrete mucus in response to tactile stimuli from luminal contents, lubricant and binds ingested material to form feces
47
Q

What do goblet cells do in the colon?

A
  1. secrete mucus in response to tactile stimuli from luminal contents
  2. secrete lubricant to protect epithelium
  3. binds ingested material to form feces
48
Q

What are the histological features of the colon?

A

NO VILLI
All crypts
On top of a BASEMENT MEMBRANE

49
Q

What happens if you have a thick basement membrane in colon?

A

You cant absorb water and you get diarrhea

50
Q

Does the amount of lymphocytes and plasma cells in colon signal abnormality?

A

NO because impossible to tell what is normal

51
Q

Where are the lymph vessels of colon located?

A

Beneath muscularis mucosae so it is harder for muscle to spread

52
Q

What usually has more lymph metastases, small or large intestines?

A

Small intestine because lymph is in lamina propria (in between surface epithelium and muscularis mucosae

53
Q

What are the architectural/histological features of the rectum?

A
  1. a bit irregular architecture
  2. shows lymph vessels only below muscularis mucosae
  3. shows paneth cells increasing from proximal to distal sites
  4. shows villi for active iron absorption
  5. shows rgular crypts reaching through muscularis propia
54
Q

Are paneth cells located in the colon?

A

Yes

Located in ½ of colon

55
Q

What type of lymphoid tissue is associated with mucosa?

A

Mucosa-associated lymphoid tissue (MALT)

Protects from enormous quantity of antigens

56
Q

What are M cells?

A

Stands for microfold cells
Found in follicle associated epithelium of Peyer’s patch
They transport organisms and particles from the gut lumen to immune cells across epithelial barrier

57
Q

What ig’s are made by B cells in Peyer patches?

A

IgA and IgM

58
Q

When do you see T-cells in esophagus?

A

In reflux disease

NO SIGNIFICANT lymphoid tissue in esophagus

59
Q

When do you get lymphoid cells in stomach?

A

During chronic gastritis

Lamina propria usually contains no lymphoid cells

60
Q

What is the key disease in the SMALL INTESTINE that leads to accumulation of T-cells?

A

Celiac disease

61
Q

What is the key disease in the LARGE intestine that leads to accumulation of T-cells in surface epithelium?

A

Lymphocytic colitis

GI Week 1 (6 decks)

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