Gastroduodenal Mucosal Protection, Ulcers Flashcards
what’s the most important function of GI tract?
ability to regulate trafficking of macromolecules between environment and host through barrier mechanism
functions of GI barrier
efficient transport of nutrients
protect epithelial cells
list GI barrier components
osmotic permeability
stem cells - support repair
bicarb microclimate adjacent for H gradient
mucus gel layer
immune defense
list the three components of mucosal barrier
tight junctions
mucus layer
immune cells
what makes the microenvironment separating lumen and apical membrane?
glycocalyx
mucus
unstirred water
___ cells secrete layer of mucus
goblet
where in GI is the mucus layer thickest?
colon
mucus layer consists of ___.
mucin
is the mucus gel layer static?
NO
abrasion can remove pieces
low pH cases sloughing
what triggers mucus secretion?
vagal stim
physical/chemical irritation
what creates a neutral character of mucus gel layer?
unstirred water and bicarb secretion
bicarb remains in mucus gel
PGE2 stim bicarb secretion, inhibits gastric acids
what are paneth cells?
granulocytes in SI crypt
what are peyers patches?
lymphatic tissue masses in SI (ileum)
what are the two types of PRR’s in GI?
TLR
NOD-like receptor aka NLR
what do paneth cells synthesize and secrete?
antimicrobial peptides
alpha-defensins aka cryptdins
how do commensal bacteria provide protection?
inhibitory compounds
compete for adhesion sites
modulate response
what is inflammatory bowel disease?
chronic inflammation of GI tract
breakdown of regulatory mechanisms that cooperate to maintain GI homeostasis
**excessive normal function
describe how IBD is a multifactorial disease?
what are two disruptions of GI barrier?
toxicity of NSAID/heliobacter/parasites
ischemia
how are epithelial cells qucikly repaired?
stem cells in neck of crypts
what are ulcers?
disruption to mucosal integrity
excessive exposure to acid
what are two causes of excess acid exposure (causing ulcers)?
- caused by excess gastric acid production
- caused by damage to mucus gel layer while acid production stays normal
PG are quickly synthesized by…
COX path
NSAID ____ COX pathway
inhibit
NSAID toxicity effects on the following…
mucus
bicarb
blood flow
cell restitution
inflammation
how can NSAIDs become trapped in epithelial cells?
neutral pH of inner cell lumen causes trap in ionized form
what are aspirin side effects?
V, D, mucosal erosion, ulcer, black stool
aspirin overdose signs
V, D, appetite loss, acid/base issue, seizure, coma, dead
what is heliobacter pylori?
gram negative bacteria
infection linked to gastritis, peptic ulcer, higher gastric neoplasia rate
what does helicobacter pylori do to its flagella, and pH?
burrows flagella into mucus layer, increases pH
the presence of parasites in GI causes…
- mechanical damage to mucus layer and mucosa
- chronic exposure to acidic environment
- inability to repair cells
two types of GI ischemia
non-occlusive
occlusive
what is occlusive ischemia?
directly disrupt GI blood flow
what is non-occlusive ischemia?
due to reduced capillary blood flow or shunting away from GI tract
ex: stress, cushings
