The human digestive system breaks down food through a multi-step process. In the mouth, saliva containing the enzyme amylase begins to break down starches. The stomach further breaks down food using gastric juices containing hydrochloric acid and the enzyme pepsin. The partially digested material then moves to the small intestine where pancreatic juices containing enzymes like trypsin and lipase and bile from the liver finish the breakdown into absorbable molecules. These molecules are then absorbed through the intestinal walls and transported throughout the body. Undigested material moves to the large intestine where water is absorbed before elimination of waste.

1. Human digestion

2. Human digestive system (General plan)Accessory digestive organs

3. Sites of digestionPolysaccharides(starch, glycogen)Disaccharides(sucrose, lactose)Salivary amylaseSmaller polysaccharides,maltoseProteinsPolysaccharidesPepsinPancreatic amylaseSmall polypeptidesMaltose and other disaccharidesPancreatic trypsin and chymotrypsinDNA, RNAFat globules PancreaticnucleasesBile saltsDisaccharidasesFat droplets Smaller polypeptidesNucleotidesPancreatic lipaseGlycerol, fattyacids, glyceridesMonosaccharidesNucleotidasesSmall peptidesNucleosidesDipeptidases, carboxypeptidase, aminopeptidaseNucleosidases, phosphatasesNitrogenous bases,sugars, phosphatesAmino acids

5. Digestion in the MouthSalivary glandsWaterSome enzymesSalivary amylaseLysozymeMucus or mucinTeeth

6. Swallowing: from mouth to stomach

7. Digestion in the StomachMuscular sac

8. Churns & mixes food

9. Gastric glands

10. Parietal cells HCl, intrinsic factor

11. Goblet cells mucus

12. Chief cells pepsinogen, weak gastric lipase

13. Gastrin

14. Hormone

15. Controls gastric juices

16. Comes out as chyme (2-6 hours)LiverSecretes bile (stored in gall bladder)Emulsifies fatsGallbladderStores, concentrates, and releases bile into duodenum

17. Stimulated by the hormone cholecystokinin (CCK)PancreasExocrine functionAcinar cells secrete pancreatic juiceAmylaseLipaseTrypsinChymotrypsinCarboxypeptidaseNucleaseNaHCO3Secretin and cholecystokinin (CCK)fr intestinal wall stimulates PJ production