Histology of Alimentary Tract

Question 0

What does “mucosa” refer to in the GI tract?

Answer 0

The innermost 3 layers: epithelium, lamina propria, muscularis .

Question 1

7 layers of tissue in the GI tract, from inside out?

Answer 1

Epithelium
Lamina propria
Muscularis mucosae
Submucosae
Inner muscle layer (circular)
Outer muscle layer (longitudinal)
Adventitia or serosa

Question 2

Where are the 2 layers of nerve plexuses?

Answer 2

In the submucosal layer (Meisner’s)

Between the muscularis propria layers (Meyenteric / Auerbach’s)

Question 3

CTB review: 3 ways to stick cells together?

Answer 3

Tight junctions
Desmosomes
Gap junctions

Question 4

Why are there acini in the esophagus?

Answer 4

To secrete saliva, to keep the esophagus lubricated.

Question 5

3 different histological regions of the stomach? (slightly different from Dr. White’s divisions)

Answer 5

Cardia
Corpus
Antrum

Question 6

What are the little dots on the rugae?

Answer 6

Gastric pits, where glandular cells live.

Question 7

Which cells make stomach acid?

Answer 7

Parietal cells.

Question 8

What tells the parietal cells to make acid?

Answer 8

Gastrin and histamine.

Question 9

What cells make gastrin?

Answer 9

Antral neurendocrine cells (G cells)

Question 10

What cells make histamine, and what tells them to do so?

Answer 10

Enterochromaffin-like cells make histamine in response to gastrin.
(histamine acts paracrine)

Question 11

Should there be inflammatory cells in the lamina propria of the stomach?

Answer 11

No.

Question 12

What do parietal cells look like on H&E?

Answer 12

Very pink cytoplasm.

“P” for parietal, pink, and pH

Question 13

What do chief cells make?

Answer 13

Digestive enzymes, such as pepsinogen.

Question 14

Where are the parietal cells mostly?

Answer 14

In the corpus/fundus (less so in the antrum).

Question 15

Where in the GI tract is most of the lymphoid aggregation?

Answer 15

In the ileum and colon.

Question 16

Should T cells be in the epithelium of the small intenstine?

Answer 16

Apparently not.

Question 17

What are the lymph vessels of the lamina propria called?

Answer 17

Lacteals

Question 18

What do paneth cells look like? What do they do? Where are they?

Answer 18

Eosinophilic granules, secrete microbial peptides, in the “small intestine”

Question 19

What do Brunner glands do? What layer are they in? Where are they found?

Answer 19

These are submucosal glands of the duodenum that secrete alkaline stuff to neutralize acid chyme.

Question 20

What does the colon absorb?

Answer 20

Water, Na+, Cl-

when colon is inflamed and can’t absorb well, water stays in lumen -> diarrhea

Question 21

Why is it significant that the lymphatics of the colon are so deep?

Answer 21

Cancer takes a long time to invade that deeply to metastasize.
(contrasted with small intestine)

Question 22

What are the lymphocyte follicles in the small intestine called?

Answer 22

Peyer’s patches

Question 23

What special cells are antigens in the gut lumen transcytosed through? (How do they look different from other epithelial cells?)

Answer 23

M cells. They don’t have microvilli (no brush border).

Question 24

What do B cells in the gut make a lot of? Proposed function?

Answer 24

They make a lot of IgA and IgM.

These are thought to be very important in preventing pathogens from adhering to the gut epithelium.

Question 25

Do the esophagus and stomach normally have lymphoid tissue?

Answer 25

Nope.