digestion of metabolites in the intestines

digestion of carbohydrates

digestion of proteins

micro-anatomy

villi

finger-like projections into the lumen which are covered in enteroctyes (which have microvilli on their apical surface)

contain a network of capillaries (all other nutrients go here) and a lacteal (dietary fat goes here)

intestinal crypts (mucosal glands)

rich in lymphocytes, eosinophils, and plasma cells

they also contain a few goblet cells

bordered on the bottom by the muscularis mucosae

digestion of lipids

only monosaccharides can be absorbed by enterocytes

pepsinogen (from chief cells) is activated to pepsin which cuts up proteins into amino acids and oligopeptides

trypsin (from pancreatic acinar cells) and other proteases further cleave peptides

triglycerides are broken down by lipases into 1 monoglyceride and 2 fatty acids

cholesterol esters are broken down by cholesterol ester hydrolase into 1 cholesterol and 1 fatty acid

phospholipids are broken down by phospholipase A2 into 1 lysolecithin and 1 fatty acid

lipid breakdown products enter the lacteal of a villi

protein breakdown products enter the capillary of a villi

monosaccharids enter the capillary of a villi