2 Physio: GI overview

function:
- conversion of macromolecules into absorbable micromolecules via mechanical and chemical means
- diet--> circulatory system

3 processes:
1. motility: smooth m contractions crush, mix, and propel contents= mechanical digestion
2. secretions: digestive enz, mucus, ions and fluid create aqueous phase= chemical digestion
3. absorption: transport of nutrients, water, ions across epithelium into blood or lymph

control systems:
- hormonal and neural:
1. adjust GI activity to quality/ quantity of incoming food
2. facilitate communication b/w GI sections

mouth:
- mechanical breakdown of food
- addition of saliva as lubricant

esophagus:
- conduit mouth--> stomach

stomach:
- chem digestion of proteins
- liquefecation of food
- start of protein digestion

liver/bile:
- provision of bile salts for digestion/ absorption of fats

pancreas:
- provision of major digestive enzymes

SI:
1. provision of enzymes
2. chemical digestion
3. absorption of nutrients and water

LI:
1. absorption of water
2. feces formation
3. bacterial fermentation: major spp differences, all spp

rumen/ forestomach:
- bacterial fermentation of nutrients
- absorption of fermentation products

proteins:
4-20aa: oligopeptide
> 20 aa: polypeptide

lipids:
- average 18-20 aa