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ANAT 261 > Esophagus, Stomach, Small and Large intestine > Flashcards

Esophagus, Stomach, Small and Large intestine Flashcards

1
Q

What are the components of the general plan of the GI tract (from esophagus → large intestine)?

A

Mucosa:
- Epithelium
- Lamina Propria
- Muscularis Mucosae

Submucosa → Loose or Dense CT

Muscularis:
- Internal (circular)
- External (longitudinal)
*Stomach has a 3rd layer

Serosa (or Aventitia) → Loose or Dense CT depending where

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2
Q

What is the general plan specifically in the esophagus like?

A

Mucosa:
- Epithelium → Non keratinize squamous stratified epithelium
- Lamina Propria → Loose CT
- Muscularis Mucosae

Submucosa → Loose or Dense CT
- Contains esophageal glands that secrete mucous to lubricate the dry food

Muscularis:
- Internal (circular)
- External (longitudinal)

Adventitia Mucosa:
- Epithelium
- Lamina Propria
- Muscularis Mucosae

Submucosa → Loose or Dense CT

Muscularis:
- Internal (circular)
- External (longitudinal)
*Stomach has a 3rd layer

Adventitia → Loose or dense CT depending

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3
Q

What are the main actions of the stomach in food digestion?

A

Add an acidic fluid to the ingested food to transform it into viscous mass called “chyme”

pH ~ 2.0

  • Stomach also secretes intrinsic factor essential to absorb vitamin B12
  • Produces hormones which will act later in the GI tract such as gastrin
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4
Q

What are the different areas of the stomach?
What allow to differentiate them?

A

Cardia → 1:1 (Pit : Gland length)
Fundus
Body → 1:3 (Pit : Gland length → much longer glands)
Pylorus → 2:1 (Pit : Gland length → longer pit)

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5
Q

What are the portions of the stomach epithelium?
Which cells are found where?

A

Pit → Surface mucous cells

Neck of the Gland → Mucous Neck cells + Parietal cells

Base of the Gland → Zymogenic cells + Parietal cells

*1 continuous layer of epithelial cells resting on a basement membrane

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6
Q

What are the characteristics of surface mucous cells?
*Stomach

A

Carbohydrate-rich glycoproteins described as the visible mucus because of its cloudy appearance → forms a thick viscous gel-like coat that adheres to the epithelial surface
Its high concentration of bicarbonate → local buffer to neutralize the acid so it doesn’t eat up the cells

  • Mucous granules → stained dark in EM bc electron dense structures
  • Centrally located nucleus
  • Many mitochondrias
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7
Q

What are the characteristics of mucous neck cells?

A
  • Have a triangular/neck appearance
  • The mucous they secrete is more soluble as it allows other substances to pass through the lumen of the gland (secretory granules)
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8
Q

What are the characteristics of Zymogenic cells?
*Stomach

A

Secrete Zymogenic Granule → help with breakdown of food later in the GI tract, but released in the lumen of the stomach

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9
Q

What is common to all epithelial cells lining the stomach?

A
  1. Rest on a Basement membrane
  2. Have microvili on their apical surface
  3. They are connected by tight junctions
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10
Q

What are the characteristics of Argentaffin cells?
*Stomach

A

Also called enter-endocrine cells

Release argentaffin granules → Gastrin, Serotonin, Histamine, VIP, Glucagon, Somastotatin → hormones are released through the BASEMENT MEMBRANE

*Called this way because the proteins stain well in silver-stains

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11
Q

What are the characteristics of parietal cells?

A

*Also called Oxyntic cells

  • Secrete intrinsic factor → for absoprtion of Vitamin D12
  • Have canaliculi with microvilli in them → more suface area
  • BIG centrally located nucleus (looks like a fried egg)
  • Secrete HCl → acidify the stomach
    *Have Carbonic Anhydrase: CO2 + H2O → H+ + HCO3-
    With Cl- → HCl
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12
Q

What disease/condition is caused by malfunction of the parietal cells?

A
  • Atrophic Gastritis
  • Pernicious Anemia
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13
Q

What is the main role of the small intestine in digestion?

A
  1. Macromolecules are terminally digested in the SI → action of Pancreatic Enzymes
  2. Terminal digestion occurs on the mucosa wall
  3. Amino acids, monosaccharides, fatty acids, monoglycerides are absorbed along the vast absorptive surface of the SI
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14
Q

What allows histological differentiation of the Duodenum, Jejunum and Ileum?

A

At the level of the submucosa (Dense CT):

Duodenum:
- Thick submucosa filled with Brunner’s glands → secrete alkaline fluid in bicarbonate (pH~9.0)
- Secretions mix with and neutralizes the acidic stomach contents to allow pancreatic enzymes to be active in their optimal neutral pH

Jejunum:
- Submucosa forms Plicae Circulares which are “eruptions” that push the mucosa up into peaks → allows to further increase surface area for better absorption of nutrients (in addition to crypts and villi)
- Increase surface area ~3x
- Extend around 1/2 - 2/3 of the circumference of the small intestine

Ileum:
- Thin boring submucosa

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15
Q

In the small intestin, is it an Adventitia or a Serosa?

A

Serosa

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16
Q

How is the epithelium of the mucosa of the small intestin classified?

A

Simple columnar epithelium

17
Q

Which different cells are found in the villi of the SI?

A
  1. Columnar cell with brush border (Absorptive cells/Enterocytes)
  2. Goblet cells → secrete mucous for lubrication (not protection, thinner mucous than surface mucous cell which allows protection)
  3. M cells (Microfold cells) → aggregate into Peyer’s patches/Gut Associated Lymphatic Tissue and secrete Ab

*Form a simple columnar epithelium

18
Q

Which cells are found in the crypts of the SI?

A
  1. Columnar cell with brush border (Absorptive cells/Enterocytes)
  2. Goblet cells
  3. Enterendocrine cells → secrete under the BM
  4. Paneth cells (Lysozymes) → control microbiome by regulating the killing of bacteria
  5. Stem cells → division and rapid turover
    *Form a simple columnar epithelium
19
Q

What is the turnover rate of the SI epithelium?

A

3-10 days → very active stem cells at the base of the crypts

20
Q

What is secreted by enteroendocrine cells in the crypts of the SI?

A

Cholecystokinin (CKK) → promotes contraction of gall bladder and pancreatic secretions into the duodenum

21
Q

How are the different digested nutrients absorbed into enterocytes?

A

Amino Acids + Monosaccharides (hydrophilic) → go through plasma membrane → through BM → blood vessels (passive)

Monoglycerides, Fatty Acids, Cholesterol, Phospholipids (hydrophobic) →Endocytosed → brough to the smooth ER (SER)
- Apoproteins are synthesized in the rough ER
In the Golgi, Chylomicrons are formed for transport of lipids to the liver for further digestion

22
Q

What are different parts/features of enterocytes in the SI?

A
  1. Microvilli at their apical surface
  2. Connected to neighbouring cells by 3 types of connections (apical → basal)
    - Tight junctions
    - Zonula Adherens (form belt around, at level of the terminal web)
    - Desmosomes
23
Q

What protein are found at the level of the microvilli in SI enterocytes?

A
  1. Actin forms rod-like bundles
  2. At the top of actin rods (tip of the microvilli) → Dense matrix (villin = actin binding protein)
  3. Actin filaments interact with Myosin at the level of the terminal web → contraction allows movement of the microvilli
  4. At the top, on the outside, different enzymes are responsible to digestion, absorption and IgG absorption (passive immunity from mother to its baby when drinking breast milk)
24
Q

Which enzymes are found at the surface of the microvilli of SI enterocytes?

A
  • Glycoproteins
  • Disaccharidases
  • Dipeptidases
  • Alkaline Phosphatase
  • Enterokinase (duodenum): Cleaves trypsinogen → trypsin (active)
25
Q

How to M cells act in the case of need?

A
  1. basal lamina becomes discontinuous to allow passage of lymphocytes
  2. M cells allows uptake of lymphocytes from circulation to release them in the GI tract → make Ab
26
Q

What are the different sections of the large intestine (colon)

A
  1. Vermiform appendinx
  2. Cecum (entry for SI contents)
  3. Ascending, Transverse, Descending colon
  4. Sigmoid colon
  5. Rectum
27
Q

What is the general plan of the colon? (different layers)

A

Mucosa → ONLY crypts (no villi):
- Simple columnar epithelium
- Lamina Propria
- Muscular mucosa (1 circular layer)

Submucosa

Tunica muscularis:
- Inner circular
- Outer longitudinal → TENIAE COLI

Serosa

28
Q

What is the Teniae coli?

A

It is the outer longitudinal smooth mucle layer of the tunica muscularis in the large intestin/colon

Smooth muscles form bundle ~3 length-wise → allows to generate more force to push the leftover contents down to the rectum

29
Q

What different cells are found in the epithelium of the colon/large intestine?

A
  1. Goblet cells (LOTS of them)
  2. Absorptive cells
  3. Entero-endocrine cells
  4. Stem cells
30
Q
A

ANAT 261 (21 decks)

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