Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Functions of the Digestive System  Food breakdown as mechanical digestion  Breaking large pieces into small pieces (increase surface area)  Prepares food for further degradation by enzymes  Examples:  Mixing food in the mouth by the tongue  Churning food in the stomach  Segmentation in the small intestine

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Functions of the Digestive System  Food breakdown as chemical digestion  Enzymes break down food molecules into their building blocks  Each major food group uses different enzymes  Carbohydrates (polysaccharides/starches) are broken to simple sugars monosaccharides/glucose)  Proteins (peptides) are broken to amino acids  Lipids (Fats) are broken to fatty acids and glycerol *Cellulose is a carbohydrate that cannot be broken down by our digestive system and is referred to as ruffage or fiber- it helps clean the system

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Accessory Digestive Organs  Teeth  Salivary glands  Pancreas  Liver  Gallbladder

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Teeth  Function is to masticate (chew) food  Humans have two sets of teeth  Deciduous (baby or “milk”) teeth  20 teeth are fully formed by age two  Permanent teeth  Replace deciduous teeth between the ages of 6 and 12  A full set is 32 teeth, but some people do not have wisdom teeth (third molars)  If they do emerge, the wisdom teeth appear between ages of 17 and 25

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Salivary Glands  Three pairs of salivary glands empty secretions into the mouth sublingual parotid submandibular

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Saliva  Contains mucus, helps to form a food bolus  Contains salivary amylase to begin starch digestion  Has antimicrobial properties and contains phagocytes  Dissolves chemicals so they can be tasted  Is continuously made throughout the day, peeking in the afternoon  Can also be stimulated to produce more saliva at other times (mouth waters)

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Pancreas  Found posterior to the parietal peritoneum  Extends across the abdomen from spleen to duodenum  Connected to the duodenum via various ducts

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Pancreas  Produces buffer (alkaline substance)  Neutralizes stomach acids still in the chyme  Produces enzymes  Pancreatic amylase: continues the breakdown of starch into glucose  Protease: breaks proteins into amino acids  Lipase: breaks fat into fatty acids and glycerol

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Liver  Largest gland in the body  Located on the right side of the body under the diaphragm  Consists of four lobes  Connected to the duodenum via the common hepatic duct

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Liver  Produces bile: a yellow-green substance  Physically breaks down fat to increase surface area: process known as emulsification  Stored in the gall bladder

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Gall bladder  Sac-like structure  Found embedded in the lower liver  Stores bile backed up in the duct  Hormonally controlled to release bile to duodenum