3. GI cellular anatomy Flashcards Preview

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Flashcards in 3. GI cellular anatomy Deck (17)
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1
Q

name the 4 layers of the GI tube

A
  1. mucosa (innermost)
  2. submucosa
  3. inner circular and outer longitudinal muscle layers
  4. serosa (continuous with mesenteries)
2
Q

name the 3 layers of the GI mucosa and state their function

A
  1. epithelium (innermost) - absorption and mucus/hormone production
  2. lamina propria - contains lymph nodules and macrophages, produces IgA
  3. muscularis mucosae - SM layers in diff. orientations to keep epithelium in contact with gut wall and help keep crypt contents dynamic
3
Q

which antibody type is produced by the GI mucosa

A

IgA - resistant to proteases

4
Q

where are the 2 enteric plexuses found

A
  1. submucosal/Meissener’s plexus - submucosa

2. myenteric/Auerbach’s plexus - inner circular muscle layer

5
Q

what type of epithelium is found in the gut and why

A
  • stratified squamous in oesophagus and distal anus - withstands abrasion
  • simple columnar - absorption
6
Q

name the area of division in the anal canal and the differences on either side of the line

A
  • PECTINATE LINE
  • above 2/3 = simple columnar epithelium derived from endoderm of hindgut
  • lower 1/3 = stratified squamous derived from proctoderm ectoderm
7
Q

name the most common cell of the GI epithelium and describe its characteristic features

A
  • ENTEROCYTE
  • have microvilli (forming brush border) to increase surface area for absorption and digestion via enzymes
  • short lifespan (2-4 days): prevents bowel perforation and can adapt to nutrient changes
8
Q

which cells produce mucus in the GI tract - describe their shape

A
  • GOBLET CELLS
  • increase in no. from duodenum to colon
  • narrow base and larger apical end, mucus droplet compresses nucleus to base
9
Q

describe 4 functions of mucus in GI tract

A

protects epithelia from:

  1. friction (acts as lubricant)
  2. chemical damage (acidic environment)
  3. bacterial inflammation (forms physical barrier)
  4. food source for normal intestinal flora
10
Q

which type of mucus-secreting cell is found in the stomach?

A
  • GASTRIC SURFACE MUCOUS CELLS (foveolar cells)
  • line most of gastric mucosa/gastric pits
  • secrete mucus/HCO3 (higher pH than other mucus) that forms barrier to stomach acid
11
Q

name 4 structures that increase surface area for absorption in GI tract

A

permanent folds

  1. plicae circulares
  2. villi (in small intestine, not colon)
  3. microvilli

temporary folds
4. rugae (for stomach expansion)

12
Q

in which areas of the GI tract are crypts of Lieberkuhn found

A

small and large intestine

13
Q

name 5 different cell types found in the crypts

A
  1. enterocytes
  2. goblet cells
  3. enteroendocrine cells
  4. stem cells
  5. paneth cells
14
Q

what is the function of stem cells in the crypt

A

migrate up to renew epithelium

15
Q

what is the function of enteroendocrine cells

A

secrete hormones

16
Q

what is the funciton of paneth cells

A

secrete antibacterial proteins to protect stem cells

17
Q

which type of exocrine gland is found in the duodenum

A

tubular BRUNNER’S GLANDS - secrete HCO3- rich mucus to neutralise acidic chyme