5.2 Digestive System Histology

Question 1

Other than water, what is in saliva?

Answer 1

• IgA antibodies
• Electrolytes
• Enzymes

Question 2

What are the two types of saliva secretory cells? What are the three corresponding types of salivary gland?

Answer 2

Cells: protein (serous), mucin (mucous)
Acini: protein, mucous, mixed

(remember, acini is the chamber where the products are secreted, like the acinar cells of the pancreas)

Question 3

There are two main muscular layers in the GI tract (not including the circular vs longitudinal). Where is the less obvious one, and what is it called?

Answer 3

• Lamina muscularis mucosae
• Superficial to submucosa

Question 4

Describe the muscularis layer of the oesophagus superiorly to inferiorly

Answer 4

Superiorly (upper 1/3): striated

Inferiorly (lower 2/3): transitions to smooth muscle

Question 5

Describe the mucosal epithelium of the oesophagus. Why does this make sense?

Answer 5

• Thick, squamous, non-keratinized
• Needs to be protected in the case of sharp foods

Question 6

Describe the epithelium of the stomach

Answer 6

• Single layer columnar epithelium
• Contains gastric pits and glands

Question 7

How does the stomach inform the body/rest of the GIT what’s going on?

Answer 7

With endocrine cells:
- G cells (gastrin)
- ECL cells (histamine)
- D cells (somatostatin)

Question 8

Which cells produce pepsinogen? How is it activated?

Answer 8

• Chief cells
• Activated by acidic environment

Question 9

Which cells produced soluble mucous inn the stomach?

Answer 9

Surface mucous cells.

Question 10

Which cells produce stomach acid and intrinsic factor (acid is intrinsic to the stomach)

Answer 10

Parietal cells.

Question 11

What do Brunner glands in the duodenum release? In what GI layer are they located? What triggers this?

Answer 11

• Release alkaline rich mucous to neutralise acid
• Located in submucosa
• Stimulated by vagus nerve and by secretin (from S cells)

Question 12

Intestinal juice is released from _________ crypts

Answer 12

Lieberkuhn. (Like leberkase)

Question 13

Histologically, how is the duodenum’s surface area maximised?

Answer 13

• Plicae circulares (circular folds)
• Villi/microvilli

Question 14

What can be found inside an intestinal villus? Why?

Answer 14

• Artery/vein/lymph lacteal (fat)
• Fibroblasts (for CT)
• Plasma cells (IgA)

Question 15

What cells can be found inside an intestinal crypt? Why?

Answer 15

• Stem cells (replenish)
• Paneth cells (antimicrobial peptides)
• Endocrine (CCK, GLP-1, Secretin)
• Chemo-sensory tuft cells

Question 16

Intestinal M cells function

Answer 16

Sample and transport antigens to MALT beneath.

Question 17

True or false: there are few goblet cells in the colon.

Answer 17

• False
• There are many

Question 18

Summarise the histology of the colon

Answer 18

• Single columnar epithelium
• No villi (but crypts)
• No brunner glands
• Many goblet cells
• Almost no lymphatics
• Haustrae and teniae coli