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

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

Accessory Digestive Organs Teeth Salivary glands Pancreas Liver Gallbladder

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

Salivary Glands Three pairs of salivary glands empty secretions into the mouth parotid sublingual submandibular

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)

Pancreas Found posterior to the parietal peritoneum Extends across the abdomen from spleen to duodenum Connected to the duodenum via various ducts

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

Liver (Hepa- 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

Liver Produces bile: a yellow-green substance Physically breaks down fat to increase surface area: process known as emulsification Stored in the gall bladder

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