The document summarizes the human digestive system. It describes the organs and sites involved in mechanical and chemical digestion of carbohydrates, proteins, nucleic acids, and lipids. These include the mouth, esophagus, stomach, small intestine, pancreas, liver and gallbladder. Enzymes produced at each site break down nutrients into smaller molecules that can be absorbed in the small intestine. Hormones regulate secretion of digestive juices from the stomach, pancreas, liver and gallbladder.

1. Human digestion

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

3. Sites of digestion Organ/s Mechanical digestion Carbohydrate digestion Protein digestion Nucleic Acid digestion Lipid digestion Oral cavity Esophagus Pharynx Chewing Peristalsis Stomach Churning Mixing Peristalsis Small intestine Lumen Peristalsis Mixing Small intestine Epithelium Polysaccharides (starch, glycogen) Disaccharides (sucrose, lactose) Salivary amylase Smaller polysaccharides, maltose Polysaccharides Pancreatic amylase Maltose and other disaccharides Disaccharidases Monosaccharides Proteins Pepsin Small polypeptides Pancreatic trypsin and chymotrypsin Smaller polypeptides Small peptides Dipeptidases, carboxypeptidase, aminopeptidase Amino acids DNA, RNA Pancreatic nucleases Nucleotides Nucleotidases Nucleosides Nucleosidases, phosphatases Nitrogenous bases, sugars, phosphates Fat globules Bile salts Fat droplets Pancreatic lipase Glycerol, fatty acids, glycerides

4. Composition of the adult human body

6. Swallowing: from mouth to stomach

11. Chemical digestion in the duodenum (con’t.)

12. Absorption in the small intestine

14. Hormones coordinate secretion of digestive juices Name Source Stimulant Target Organ Function Stomach Gastrin Pyloric mucosa Partially-digested food Gastric glands Secretion of gastric juice Intestinal Gastrin Intestinal mucosa Stomach Secretin Acidity of chyme Pancreas and liver Secretion of PJ rich in HCO 3 - and bile production Cholecystokinin (CCK) Fats or combination of acids and fats Pancreas and gallbladder (Sphincter of Oddi in CBD) Secretion of PJ, bile from gallbladder, opening of SO Enterocrinin Acidity of chyme Duodenum Secretion of intestinal juice Enterogastrone or Gastric Inhibitory Peptide (GIP) Fats Stomach Inhibits secretion of gastric juice and decreases gastric motility

15. Liver Gall- bladder CCK Entero- gastrone Gastrin Stomach Pancreas Secretin CCK Duodenum Key Stimulation Inhibition