Ch.2 - Colonic Physiology Flashcards
Three main cell types present in the colonic epithelium?
Columnar epithelial cells
Goblet cells
Enterochromaffin cells
What enteric plexus is in the submucosa?
What enteric plexus is between the inner circular and outer longitudinal muscles?
Meissner plexus in the submucosa
Auerbach plexus between the muscles
What is the main source of the substrate for colonic nutrition?
Explain how this substrate provides energy for colon
Undigested dietary fiber -> metabolized by colonic bacteria [fermentation] -> the end product of this process include short chain fatty acids including butyrate (main source of energy for colonocyte) and gas
Lignin and psyllium are not metabolized at all but remain as hydrophilic molecules in stool -> water retention and stool bulking
Why is increased stool bulk good?
Increased stool bulk ->
1) improved stool transit, decreased time of exposure of colonic lumen to toxin produced by protein fermentation
2) decreased intracolonic pressure
This is why we recommend dietary supplementation of indigestible fiber
These toxin can lead to mucosal injury, reactive hyperproliferation, possible promotion of carcinogenesis
What does butyrate have anything to do with antibiotic induced diarrhea?
Abx kills bacteria -> less bacteria to ferment undigested dietary fiber -> less butyrate absorption -> less active Na/H/ATP pump -> net secretion of fluid
What are the two layers of the mucous secreted in the colon
Inner layer: sterile, dense gel containing antimicrobial peptides, enzymes, IgA
Outer layer: contains bacteria, lubricates feces
What are the intrinsic vs extrinsic pathways of innervation for the colon?
Extrinsic: sympathetic & parasympathetic input
Intrinsic: myenteric plexus
What is the pacemaker cell of the intestine?
Interstitial cells of Cajal.
JIST
What is HAPC?
What is it’s role? what pressure? How many times a day?
High Amplitude Propagated Contractions
To move stool in bulk.
6 times a day, >75mmHg
