digestion basics

two types of digestion + definitions

• physical digestion - breakdown of large food pieces into smaller ones to increase the surface area for chemical digestion

• chemical digestion - enzymes catalyse hydrolysis reactions that break bonds in large insoluble molecules to form smaller soluble molecules

structure of human digestive system

mouth & salivary glands → oesophagus → stomach → liver → pancreas → duodenum → ileum → rectum

path that food travels through

mouth → oesophagus → stomach → small intestine → large intestine → rectum → anus

function of mouth & salivary glands

teeth do physical digestion. salivary lands secrete amylase to begin to digest starch → maltose

function of oesophagus

transports food to stomach

function of stomach in digestion

protease enzymes begin protein digestion and hydrochloric acid provides suitable pH for enzymes and destroy any pathogens in food

function of liver in digestion

produces bile salts to aid lipid digestion and neutralise stomach acid as it leaves the stomach

function of the pancreas in digestion

produces amylase, protease and lipase and releases them into the duodenum

function of the duodenum in digestion

acidic stomach contents are neutralised by bile and become slightly alkaline. enzymes complete chemical digestion here.

function of ileum in digestion

food and water are absorbed into the blood via villi in the lining of the ileum

function of the rectum in digestion

stores faeces before removal via egestion through the anus