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GI Exam 1 > Histology of the Esophagus and Stomach > Flashcards

Histology of the Esophagus and Stomach Flashcards

1
Q

What are the 4 layers of the GI tract, from lumen to superficial?

A

MSMS

  1. Mucosa
  2. Submucosa
  3. Muscularis externa
  4. Serosa/adventitia
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2
Q

What is the difference between serosa and adventitia?

A

Serosa is covered by peritoneum

Adventitia is retroperitoneal.

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3
Q

When looking at all 4 layers throughout the GI tract, which layer differs considerably from region to region?

A

Mucosa, which reflects its functional activity.

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4
Q

Describe the muscosa layer.

A

Innermost layer that has 3 components:

  1. Epithelium
  2. Lamina propria
  3. Muscularis muscosae
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5
Q

Describe the submucosal layer.

A
  • Dense irregular CT + neurovasculature & lymphatics.
  • Submucosal layer in the esophagus and duodenum have glands.
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6
Q

The submucosal layer of which portion of the GI have glands?

A
  1. Esophagus
  2. Duodenum
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7
Q

Muscularis externa helps to move food.

Describe the muscularis externa layer.

A
  • Two layers of smooth muscle
      1. Inner circular layer- when it contracts, it contristics the lumen
      1. Outer longitudinal layer- when it constractions, it shortens the tube
  • In between both layers is a neurovascular plexus.
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8
Q

Describe the serosa/adventitia layer

A
  • Serosa- when the digestive tube is located the peritoneum and covered by mesothelium, it forms a serosa layer
  • Adventitia- digestive tube is located retroperitoneal and not covered by mesothelium

Whether or not it is considered serosa or adventitia depends on the location.

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9
Q

There is extrinsic (para/sympathetic) and intrinsic (ENS) innervation in the GI.

What is the parasympathetic innervation to the GI? (2)

A

The presynaptic nerves of the parasympathetic NS are the vagus n and pelvic splanchnic nerve.

  • Vagus nerve innervates until splenic flexure
  • Pelvic splanchnic nerve innervates from the splenic flexure–> down

The ganglion and the postsynpatic fibers are intramural.

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10
Q

What are the sympathetic innervation to the GI system?

A

Branches from the greater, lesser, least and lumbar splanchnic nerves synapse on [prevertebral ganglia (celiac, SM, aorticorenal and IM ganglia)]

and send postsynaptic nerves to organs via blood vessels on the peri-arterial plexus.

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11
Q

What are the main functions of the submucosal plexus of meissner and the myenteric plexus of auerbach?

A
  • submucosal plexus of meissner: controls secretions from glands
  • myenteric plexus of auerbach (located in muscularis externa)​: controls peristalsis and movements of muscularis mucosae
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12
Q

The intrinsic (enteric) innervation is responsive to what?

A

1. Local stimuli

2. Input from the ANS

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13
Q

What 2 plexuses is the intrinsic (enteric) NS made up of and where are they located?

A

2 plexuses of sensory and motor neurons that are connected by interneurons.

  1. Submucosal plexus of meissner, found in the submucosa
  2. Myenteric plexus of Auerbach, found in between the inner circular and outer longitudinal layers of the muscularis externa.
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14
Q
  • _________ axons of the parasympathetic NS–> increase motility
  • _________ axons of the sympathetic NS–> decrease motility
A
  • Preganglionic axons of the parasympathetic NS–> Increase motility
  • Postganglionic axons of the sympathetic NS–> Decrease motility
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15
Q

What is the esophagus?

A

Fibromuscular tube that sends food from [oropharynx–> stomach].

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16
Q

Does the esophagus have serosa or adventitia?

A

BOTH!

  • Thoracic esophagus–> adventitia
  • Esophagus below the diaphragm–> serosa
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17
Q

The esophagus must have glands that produce mucous to lubricate. What are these two glands and where are they located?

A
  1. Cardiac esophageal glands- located in the mucosal layer (lamina propria) near the cardia of the stomach
  2. Submucosal glands- located in the submucosal layer
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18
Q

Describe the mucosa and submucosal layers of the esophagus.

A

Mucosa

  • Cell type: Nonkeratinized stratified squamous epithelium
  • Many folds
  • Muscularis mucosae is only present at the end of the ESO because we have a lot of cardiac esophageal glands here.

Submucosal

  • Dense irregular CT + blood vessels called submucosal venous plexuses. Increases in pressure here can cause esophageal varices which are dilations of the veins
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19
Q

Describe the muscularis externa layer of the esophagus.

A

The inner circular and outer longitudinal layers differ in different segments of the ESO.

  • Upper third are controlled by skeletal muscle and are striated.
  • Middle third are controlled by skeletal and smooth muscle.
  • Lower third are controlled by smooth muscle.
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20
Q

What are the two sphincters of the esophagus?

A
  1. UES (upper esophageal sphincter) is anatomical and allows us to swallow.
  2. LES (lower esophageal sphincter) is functional and prevents reflux. It is designed to be closed.
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21
Q

What is GERD?

What happens is if it chronic?

A

GERD occurs when the LES loosens and reflux occurs. It causes chronic inflammation, ulceration, and a hard time swallowing (dysphagia).

If GERD is chronic, it can cause the [non-keratinized stratified squamous epithelium–> mucous-secreting simple columnar cells], which is called Barrett’s esophagus/metaplasia.

22
Q

Describe the changes we see at the gastroesophageal junction?

A
  • Change in cells of the mucosa:
    • As we go from the esophagus–> stomach, we go from [nonkeratinzed stratified squamous cells–> simple columnar].
  • In the stomach, the epithelium is has glands + pits.
23
Q

What are the 4 division of the stomach?

A

1. Cardia

2. Fundus

3. Body

4. Pyloric antrum, which ends at the gastroduodenal orifice.

24
Q

We can divide the stomach into two areas based on motility.

What are these areas?

A

1. Orad area

2. Caudad area

25
Q

What is the orad area?

A
  • Fundus & upper part of the body.
  • During swallowing, the orad area and LES relax to accommodate food.
26
Q

What is the caudad area?

A
  • Lower part of the body and the antrum
  • Regulates gastric emptying
27
Q

What protects the stomach lining?

A

The muscosal surface of the stomach is protected by a [gastric mucosal barrier].

28
Q

What is rugae?

Describe the lining of the stomach.

A

The stomach lining is protected by a [gastric mucosa barrier]. The mucosa and submucosa form folds covered in gastric pits called Rugae. They help to increase friction in the stomach to help break down food.

29
Q

Describe the mucosa and submucosa layers of the stomach.

A
30
Q

Muscularis externa layer of the stomach.

What is special about it?

A
  • It has 3 layers of smooth muscle: oblique SM, circular SM and longitudinal SM. The extra layer allows a more forceful contraction.
  • In the pyloric region, the circular muscle layer thickens to form the pyloric sphincter.
31
Q

Does the stomach has serosa or adventitia?

A

Serosa- loose CT and BV

32
Q

Gastric (Fundic) Glands

Where are they located?

A

Mucosa of the stomach, except where cardiac and pyloric glands are located.

33
Q

Gastric (Fundic) Glands

What is their overall structure and where do they extend from?

A

Gastric glands are simple, branched tubular glands that extend from [gastric pit–> muscularis mucosae]. More than one open into one gastric pit.

34
Q

Gastric (Fundic) Glands

What are the three regions of gastric glands?

A
  1. Ithmus- between the gastric pit and the gland below.
  2. Neck- narrow, long region
  3. Fundic- short and wide base
35
Q

What cells are located at each region of the gastric gland?

A
  1. Gastric pit
    * surface mucous cells
  2. Ithmus
    * stem cells
  3. Neck
  • mucous neck cells
  • parietal cells
  • enteroendocrine cells
  1. Fundus
  • chief cells
  • enteroendocrine
  • some parietal cells
36
Q

What are the two cells that make mucous, which is made up of 95% water and 5% mucin?

A
  1. Surface mucous cells, which line gastric pits
  2. Mucous neck cells, which are located at the neck of the gastric gland
37
Q

How is mucous made?

A

Mucous cells have apical granules that have mucin. Mucin + water on the top of the gastric mucosa, forming a protective gel. This neutralizes the pH to a basic pH.

38
Q

What are chief cells?

A

Chief cells are located fundus region of the gastric gland.

  • Has many RER in the basal region in the cytoplasm and zymogen granules that secrete pepsinogen.
  • In the presence of a acidic environment, pepsinogen is released into the lumen–> converted to pepsin, which digests proteins.
  • Exocytosis of pepsinogen occurs fast, stimulated by eating.
39
Q

What are parietal cells?

Where are they located and what do they make?

A

Parietal cells are located: at the neck and upper part of the gastric gland.

Make: HCl and intrinsic factor, a glycoprotein that binds to VB12.

40
Q

What are the three distinct features of parietal cells?

A
  1. Abundant mT
  2. Intraceullar canaliculus, which are invaginations on the apical surface and are continous with the lumen of the gastric gland.
  3. H+/K+ dependent ATPase-rich tubulovesicular system
41
Q

Where are enteroendocrine cells located?

A

Located: at all levels of fundic glands, but more prevalent at the base.

42
Q

What are the two types of enteroendocrine cells?

A
  1. Closed enteroendocrine cells
  2. Open enteroendocrine cells
43
Q

What are the two types of enteroendocrine cells?

Describe them.

A

1. Closed cells- small cells that are not exposed to the lumen of stomach. They are indirectly controlled by contents of the lumen using neural and paracrine mechanisms.

2. Open cells- exposed to the lumen of the stomach by extensions of the cytoplasm that have microvillus on them. They are controlled by chemoreceptors that detect contents of the lumen and release hormones.

44
Q

What are the GI peptide hormones made by enteroendocrine cells?

A

1. Somatostatin*

2. Ghrelin*

  1. Motilin
  2. GIP
  3. VIP
  4. Secretin
  5. CCK

8. Gastrin*

45
Q

Cardiac Glands

Where are cardiac glands located?

What is their shape?

A

Located: at the cardia of the stomach, which surrounds the esophageal orifice. Their opening are continouus with the gastric pit.

Glands: Tubular, coiled and a little branches

46
Q

Cardiac Glands

Cardiac glands are lined with what?

A

Cells that secrete mucous

47
Q

What is a HALLMARK of cardiac glands on imagining?

A

Look circular and oblique

48
Q

Pyloric Glands

What is their shape and where are they located?

A

Pyloric glands are [branched, coiled and tubular] located btwn the [fundus and pylorus].

49
Q

Pyloric Glands

Pyloric glands are lined by what?

A

Mucus-secreting cells that look like surface mucous cells.

Large and pale secretory mucus.

50
Q

Pyloric Glands

Pyloric glands are branched, coiled and tubular between fundus and pylorus and are line with mucus secreting cells (large/pale). What can be seen sometimes in the lamina propria?

A

GALT (lymph) and sometimes enteroendocrine and parietal cells

GI Exam 1 (13 decks)

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