Histology Alimentary

Question 1

what are the 3 layers throughout the alimentary canal?

Answer 1

mucosa
submucosa
muscularis propria

Question 2

What does the submucosa contain?

Answer 2

major nerves, blood vessels

Question 3

what are the sublayers of:
Mucosa
Muscularis Propria

Answer 3

mucosa - epithelium, lamina propria, muscularis mucosae

muscularis propria - circular/longitudinal layer

Question 4

in tumour staging, how are tumours generally staged in layered organs and solid organs?

Answer 4

layered - which layers involved, irrespective of size

solid organs - size

Question 5

what epithelium lines the canal? What about in the stomach and intestine?

Answer 5

canal - squamous epithelium

stomach and intestine - columnar

Question 6

In the oesophagus, which layer is strong? What is the epithelium? What’s special about the submucosa?

Answer 6

strong muscularis propria

non-keratinising squamous epithelium

has mucus glands for lubrication and pH buffering

Question 7

what are the rugae of the stomach?

What are the 2 types of mucosa and where are they primarily located?

Answer 7

folds of submucosa

non-oxyntic mucosa: mucus producing (cardia and pylorus)

oxyntic mucosa: acid and pepsinogen-producing (corpus and fundus)

Question 8

What are the gastric glands?

Answer 8

high glandular mucosa

Question 9

What are the 4 cell types in the stomach?

Answer 9

mucous cells
parietal
chief
endocrine

Question 10

what are the functions of the 4 cell types in the stomach? How do each of the cells stain?

Answer 10

mucus 45% (H&E) = secrete mucus and bicarbonate
parietal/oxyntic 15% (eosinophilic): secrete intrinsic factor and H+ions
enteroendocrine cells: secrete gut hormones
chief/zymogenic cells 30% (basophilic): secrete pepsinogen

Question 11

what 3 things does the mucous layer of the stomach do?

Answer 11

lubricant
traps bicarbonate
traps EGF to heal gastric mucosal damage

Question 12

Why is the protective mucous layer self-regulating?

Answer 12

more acid secreted by parietal cell the more bicarb created and delivered to mucous cells (buffering action)

Question 13

What fuses to the apical membrane to increase the SA of parietal cells? What are the apical canaliculi?

Answer 13

tubulovesicles with canalicular membrane

invaginations of the apical plasma membrane

Question 14

what’s the most common cause of gastric cancers? Gastric ulcers? If ulcers in the duodenum, what does that mean as opposed to ulcers in the stomach?

Answer 14

H.pylori infection or NSAIDs

duodenum: excessive acid
stomach: reduced acid but even more reduced mucous

Question 15

what’s the difference between stomach, small intestine, and large intestine in terms of surface?

Answer 15

stomach - gastric glands
small intestine - villi & crypts
large intestine - crypts

Question 16

What are the surface foldings at the level of submucosa, lamina propria, and enterocyte?

Answer 16

submucosa - Kerchring’s folds
lamina propria - villi & crypts
enterocyte - microvilli

Question 17

what are the 7 different cell types in the intestine and what do they do? Where are the stem cells?

Answer 17

M-cells: transporter and immune response
Cup cells
Enteroendocrine cells: secretory 
Absorptive enterocytes 
Goblet cells: secretory
Paneth cells: secrete immune cells
Tuft cells: chemosensory and immune response 

crypt base contains stem cells

Question 18

Food can be absorbed as solids T/F? What’s linked to inflammatory bowel diseases?

Answer 18

FALSE - only solutes

leaky tight junctions are related to inflammatory bowel diseases and Crohns

Question 19

how do osmotically active laxatives work? Explain the chloride-loss hypothesis of bacterial diarrhoea.

Answer 19

retain water in the bowel due to osmotic action

several bacterial toxins (e.g. cholera toxin) activate the adenylate cyclase of crypt enterocytes
thus elevating cAMP levels
causing the CFTR to stay “open”
the chloride efflux leads to massive secretion of water = severe diarrhea

cAMP-dependent chloride channel (CFTR)