six essential activities of the digestive system

mechanical breakdown

chewing, mixing food with saliva (bolus), churning food in stomach (chyme), segmentation

propulsion

movement of food through alimentary canal

absorption

passage of digested fragments from lumen of GI tract into blood or lymph

digestion

series of catabolic steps that involves enzymes that break down complex food molecules into chemical building blocks

ingestion

eating

defacation

elimination of indigestible substances via anus in form of feces