Describe the functions of the main regions of the digestive system, limited to: (a) mouth – ingestion, physical digestion, chemical digestion of starch by amylase (b) salivary glands – secretion of saliva containing amylase (c) stomach – physical digestion, chemical digestion of protein by protease, presence of hydrochloric acid in gastric secretions (d) small intestine (duodenum and ileum) – chemical digestion of starch by amylase, maltose by maltase, protein by protease and lipids by lipase (e) liver – production of bile and storage of glycogen (f) gall bladder – storage of bile (g) pancreas – alkaline secretion containing amylase, protease and lipase (h) ileum and colon – absorption (i) rectum and anus – egestion

State the function of the hepatic portal vein as the route taken to the liver by most of the molecules and ions absorbed from the ileum