The Digestive System Chapter 13 Why Do We Eat? What is digestion? 2 Let’s find out what happened to your breakfast today! Digestion Processing of Food (copy) • Type one • Mechanical (physical) • Chewing • Tearing • Grinding • Mashing • Mixing 4 (Copy) • Type two • Chemical • Catabolic reactions • Enzymatic hydrolysis • Carbohydrates • Proteins • Lipids Functions of the digestive system (copy) • • • • • • Ingestion Movement Digestion Secretion Absorption Excretion (Copy) • Gastrointestinal System • Includes alimentary canal and accessory organs • Accessory organs: Salivary glands, tongue, teeth, liver, gallbladder, and pancreas Steps in Digestion (Copy) • Mouth – Crushing and grinding • Stomach – Chemical Breakdown • Small Intestine – Useful material extracted • Colon – Water removal Alimentary canal (copy) 2 main functions: •Digesting and absorbing nutrients •Protecting from invasion Mouth -mechanical digestion mastication) = teeth, tongue -chemical digestion = saliva Uvula – prevents food entering the nose (COPY) Trachea - windpipe Epiglottis – safety hatch. A flap of cartilage prevents food from entering the trachea Swallowing (Copy) Sequence • Voluntary stage • Push food to back of mouth • Esophageal stage • Open esophagus • Start peristalsis 11 Oesophagus (Copy) -transfers food to stomach by peristalsis Cardiac sphincter -opens to allow food oesophagus stomach -heartburn –acid escapes stomach Peristalsis and Segmentation 13 (Copy) Stomach Stores the food you eat Digestion = chemically - breaks it down into tiny pieces = mechanical – mixes food with digestive juices acid in the stomach kills bacteria Slowly releases food into intestine Cardiac sphincter Pyloric sphincter http://18.104.22.168/images/41-AnimalNutrition/41-16-Duodenum-L.gif Small Intestine (copy) Around 6m in an adult Food takes 1-6 h to pass through Enzymes and bile are added 2 main tasks = digestion, absorption nutrients pass into bloodstream through small intestine walls Anatomy of the Large Intestine 16 Large Intestine (copy) • About 1.5 meters long • Accepts what small intestines don’t absorb. • Absorbs water and minerals from the waste matter. Liver (copy) • Directly affects digestion by producing bile • Bile is an enzyme that helps dissolve fat • Processes nutrients in the blood, filters out toxins and waste. Related Organs 19 Gall Bladder (copy) • Stores bile from the liver • Delivers bile when food is digested • Fatty diets can cause gallstones Pancreas (copy) • Produces compounds to digest fats and proteins • Neutralizes acids that enter small intestine • Regulates blood sugar by producing insulin The Organs and Positions in the Abdominal Cavity 22 Rectum and Anus (copy) • Rectum • About 15cm long • Stores waste before egesting. • Anus • Muscular ring that controls egesting.