Histology of Alimentary Tract Flashcards
What does “mucosa” refer to in the GI tract?
The innermost 3 layers: epithelium, lamina propria, muscularis .
7 layers of tissue in the GI tract, from inside out?
Epithelium Lamina propria Muscularis mucosae Submucosae Inner muscle layer (circular) Outer muscle layer (longitudinal) Adventitia or serosa
Where are the 2 layers of nerve plexuses?
In the submucosal layer (Meisner’s)
Between the muscularis propria layers (Meyenteric / Auerbach’s)
CTB review: 3 ways to stick cells together?
Tight junctions
Desmosomes
Gap junctions
Why are there acini in the esophagus?
To secrete saliva, to keep the esophagus lubricated.
3 different histological regions of the stomach? (slightly different from Dr. White’s divisions)
Cardia
Corpus
Antrum
What are the little dots on the rugae?
Gastric pits, where glandular cells live.
Which cells make stomach acid?
Parietal cells.
What tells the parietal cells to make acid?
Gastrin and histamine.
What cells make gastrin?
Antral neurendocrine cells (G cells)
What cells make histamine, and what tells them to do so?
Enterochromaffin-like cells make histamine in response to gastrin.
(histamine acts paracrine)
Should there be inflammatory cells in the lamina propria of the stomach?
No.
What do parietal cells look like on H&E?
Very pink cytoplasm.
“P” for parietal, pink, and pH
What do chief cells make?
Digestive enzymes, such as pepsinogen.
Where are the parietal cells mostly?
In the corpus/fundus (less so in the antrum).
Where in the GI tract is most of the lymphoid aggregation?
In the ileum and colon.
Should T cells be in the epithelium of the small intenstine?
Apparently not.
What are the lymph vessels of the lamina propria called?
Lacteals
What do paneth cells look like? What do they do? Where are they?
Eosinophilic granules, secrete microbial peptides, in the “small intestine”
What do Brunner glands do? What layer are they in? Where are they found?
These are submucosal glands of the duodenum that secrete alkaline stuff to neutralize acid chyme.
What does the colon absorb?
Water, Na+, Cl-
when colon is inflamed and can’t absorb well, water stays in lumen -> diarrhea
Why is it significant that the lymphatics of the colon are so deep?
Cancer takes a long time to invade that deeply to metastasize.
(contrasted with small intestine)
What are the lymphocyte follicles in the small intestine called?
Peyer’s patches
What special cells are antigens in the gut lumen transcytosed through? (How do they look different from other epithelial cells?)
M cells. They don’t have microvilli (no brush border).
What do B cells in the gut make a lot of? Proposed function?
They make a lot of IgA and IgM.
These are thought to be very important in preventing pathogens from adhering to the gut epithelium.
Do the esophagus and stomach normally have lymphoid tissue?
Nope.
