29 - GI Histology I Flashcards Preview

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Flashcards in 29 - GI Histology I Deck (43):
1

What are the four main layers (from internal to external) of the wall of the GI tract?

- Mucosa
- Submucosa
- Muscularis externa
- Serosa

2

Describe the mucosa of the GI tract

Mucosa includes...
a. Epithelium resting on a basal lamina – proximal and distal segments are stratified squamous, nonkeratinized, the rest of the tube is simple columnar
b. Lamina propria
c. Muscularis mucosae

Stratified squamous, nonkeratinized ***

3

What is in the lamina propria of the mucosa of the GI tract?

Lots of glands - very glandular in nature

4

Describe the muscularis mucosae of the mucosa of the GI tract

- Inner circular
- Outer longitudinal

Helps in the digestive process

5

Describe the serosa

Adventitia is associated with some segments of the GI tube

There are regional differences

6

What are the two enteric nerve plexuses?

- Submucosal (Meissner’s) plexus
- Myenteric (Auerbach’s) plexus

7

Describe the submucosal (Meissner’s) plexus

Parasympathetic postganglionic neurons and their processes and sympathetic postganglionic fibers; regulates the activity of the muscularis mucosae and the secretory activity of glands

*** peristalsis and gland secretion***

8

Describe the myenteric (Auerbach’s) plexus

Parasympathetic postganglionic neurons and sympathetic postganglionic fibers; regulates the activity of the muscularis externa

*** muscularis externa ***

9

Describe the layers of the esophagus

- Mucosa
- Submucosa
- Muscularis
- Outer connective tissue layer

10

Describe the mucosa of the esophagus

Epithelium and basal lamina
- Stratified squamous, nonkeratinized
- Protection against coarse-textured foods

Lamina propria - Esophageal cardiac glands

Muscularis mucosae

11

Describe the submucosa of the esophagus

Submucosa contains esophageal glands secrete mucus

12

Describe the three sections of the muscularis externa

i. Proximal 1/3 of esophagus – skeletal muscle
ii. Middle 1/3 of esophagus - Mixture of skeletal and smooth muscle
iii. Distal 1/3 of esophagus - Smooth muscle

13

What are the two layers of the outer connective tissue layer?

- Adventitia
- Serosa

14

What else is found in the esophagus?

Enteric nerve plexus

15

Describe esophageal varices

- Caused by hepatic portal hypertension
- Caused by cirrhosis of the liver
- You will see dilation of arteries with bulging varices
- On x-ray, there will be a rough appearance

16

Describe squamous cell carcinoma in the esophagus

Most common to develop carcinoma of the esophagus in the middle 1/3 of the esophagus

17

Describe Barrett's esophagus

- Stratified squamous epithelium (normal) changes to simple columnar epithelium with mucus producing cells
- This is done in response to acid reflux to protect the epithelium from
- For diagnosis, you need to see goblet cells (mucus producing cells)
- Known as metaplasia
- Barrett's is not reversible
- Can progress to adenocarcinoma of the esophagus, so Barrett's patients need to be monitored
- Adenocarcinoma occurs most commonly in the distal 1/3 of the esophagus due to its association with Barrett's

18

Describe the lymphatics of the esophagus

- Esophagus is well endowed with intramural lymphatic channels that anastomose
- Lymph flow in the upper 2/3 is usually upward, whereas lymph flow in the lower 1/3 tends to be downward
- We only see lymphatic metastasis if the cancer of the esophagus spreads to the submucosa where the lymph flow

19

What are the four regions of the stomach?

- Cardia
- Fundus
- Body
- Pylorus

20

What are rugae?

- Longitudinal folds in the undistended stomach
- Mucosa and submucosa form the folds

21

Describe the layers of the stomach

- Mucosa
- Submucosa
- Muscularis externa
- Serosa

22

Describe the mucosa of the stomach

- Surface epithelium - simple columnar, mucous cells
- Gastric pits are formed by the invagination of the surface epithelium into the lamina propria
- Glands empty into the gastric pits
- Gland regions: isthmus, neck, and base

23

Describe the muscularis externa of the stomach

- Inner oblique layer of smooth muscle
- Middle circular layer of smooth muscle - thickened at the pylorus
- Outer longitudinal layer of smooth muscle

24

What regional differences are seen in the cardia of the stomach?

- Short gastric pits
- Long glands in the lamina propria
- Simple or branched tubular glands
- Surface lining, mucous, regenerative, and DNES cells
- Few parietal cells

25

What regional differences are seen in the fundus and body of the stomach?

- Gastric pits become slightly longer
- Gastric glands are still long
- Branched tubular glands fill the lamina propria
- Isthmus region of gland
- Neck region of the gland
- Base region of the gland

26

What is the important "take home" message of the isthmus region of the glands?

***

This is the "stem cell niche" of the stomach - REGENERATIVE cells

Rapid turnover of cells - they replace ALL other cell types as they die off

***

27

What is the important "take home" message of the neck region of the glands?

***

This is where the parietal cells are - HCl secretion

Intrinsic factor is also secreted here

***

28

Describe the cells of the base region of the gland

Contains many chief (zymogenic) cells - pepsinogen

Only a few parietal cells and some mucus cells

29

Describe the regional differences seen in the pylorus of the stomach

- Deep gastric pits
- Short glands
- Branched tubular glands
- Surface lining, mucous, regenerative cells; a few parietal cells
- Enteroendocrine cells

30

What are all the cells we see in the gastric gland?

- Parietal cell
- Chief cell
- Enteroendocrine cell
- Smooth muscle fibers from the muscularis mucosae
- G cell

31

What do the cells of the gastric gland secrete?

Parietal cell
- HCl and intrinsic factor

Chief cell
- Pepsinogen

G cell
- Gastrin

32

Describe gastric ulcers

- When the harsh acidic environment overwhelms the defense mechanisms of the stomach, we get ulceration
- Deep invagination or crater forms
- Can penetrate all the way through the wall when left untreated
- When it gets into deeper layers and ulcerates blood vessels, there is bleeding from the ulcer
- Can pep

33

What structures increase the surface area of the small intestine?

- Plicae circulares (valves of Kerckring) - Circular folds of submucosa and mucosa (x3)
- Intestinal villi - Highly vascular processes of mucosa (x6)
- Microvilli - increase surface 20-fold (x20)

600 fold increase total ***

34

What are the layers of the small intestine?

- Mucosa
- Intestinal glands (cypts of Lieberkuhn)
- Submucosa
- Muscularis externa
- Serosa

35

Describe the layers of the mucusa in the small intestine

Epithelium
- Rests on basal lamina
- Mainly absorptive columnar cells (enterocytes)
- Goblet cells are interspersed, which secrete mucus

Lamina propria
- Loose connective tissue that extends into the villi and intestinal glands (crypts)

Muscularis mucosae

36

Describe the intestinal glands (crypts of Lieberkuhn)

Small AND large intestine

- Lined by simple columnar epithelium resting on a basal lamina
- Openings of the glands are located between the villi
- Classified as simple tubular glands

37

What are the three cell types of the intestinal glands (crypts of Lieberkuhn)

Small AND large intestine

- Paneth cells (lysozyme - bacterial static, acidophilic)
- Enteroendocrine cells (hormone-secreting)
- Undifferentiated cells (stem cell population - at the base (bottom) of the cell)

38

What are the two layers of the muscularis

- Inner circular layer of smooth muscle
- Outer longitudinal layer of smooth muscle

39

Describe Brunner's glands of the duodenum or "duodenal glands"

***

This is the SIGNATURE FEATURE of the duodenum
- Secrete mucus to protect duodenum from acidic chyme
- More prominent in the proximal duodenum, dissipate as you move distally

***

40

Describe celiac sprue

****

Gluten-sensitive enteropathy

4 signature histological features ****
1 - Enterocytes are disarrayed
2 - Villus atrophy
3 - Crypt (intestinal gland) hyperplasia
4 - inflammation of the lamina propria

41

Describe the jejunum of the small intestine

- No true signature features
- No Brunner's glands are found here
- Villi are still present

42

Describe Peyer's patches of the ileum of the small intestine

***

This is the SIGNATURE FEATURE of the ileum
- Lymphatic purpose
- Also contain secondary lymphoid nodules
- Villi are still present

***

43

What are M cells?

Lymph purpose
- Found in the Peyer's patches
- Look for antigenic material
- Phagocytose the antigenic material and release into the lymph for an immune response
- Constantly "testing" for immune surveillance