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The Digestive System 7th Grade Life Science Major Functions of the Digestive System • Break down ingested food • Put nutrients into the bloodstream • Remove waste from the body • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter26/animation__organs_of_digestion.html Organs of the Digestive System • • • • • Mouth Esophagus Stomach Small Intestine Large Intestine Mouth • Digestion begins here! • Teeth and tongue are used in mechanical digestion to crush the food into smaller pieces • Saliva and enzymes (Amylase) begin chemical digestion • to break down starches to sugars. Esophagus • Muscular tube connects mouth (pharynx) to stomach • Moves food downward by peristalsis, or muscular contractions • Epiglottis seals off windpipe during swallowing to prevent choking • What are sphincters? Narrow sections of the digestive tract that keep food moving the right direction • www.dnatube.com/video/29949/All-About-Peristalsis • http://www.youtube.com/watch?v=Ujr0UAbyPS4 Stomach -Lots of Churning! (mechanical) • The mechanical digestion of proteins begins here. • Muscular pouch that expands to hold your food • Hydrochloric acid (HCl) and the enzyme pepsin combine to form gastric juice A gummy coating of mucus protects the stomach lining from the strong chemicals (prevents ulcers) • Chyme, a thick liquid containing partially digested food, is produced here • Most bacteria are killed by the stomach acid but .. http://foodsafe.ucdavis.edu/html/audio/stomachache_tonight.html Small Intestine Most chemical digestion here! • Longest portion of the digestive tract! • First section or the duodenum - enzymes from accessory organs enter to aid digestion • Accessory Organs: • Liver-over 200 jobs... breaks down toxins, stores nutrients, and produces bile • Gall bladder (tiny sac below liver) stores bile that goes to the duodenum to mechanically break down fats • Pancreas sends pancreatic juice to the duodenum to neutralize stomach acid and complete the digestion of all foods http://www.zerobio.com/secretin_flash.htm Can you name the accessory organs? A. B. C. D. E. Food never touches these! • Inner surface is covered in villi and microvilli, millions of tiny finger-like projections that increase the surface area to allow absorption of nutrients from the chyme into the blood Small Intestine shape… Which of these is the correct form of the small intestine? A! Why does the small intestine have this shape? If shape B occurs, with no villi to slow the food, it would pass too quickly through the system to be absorbed. Starvation! Large Intestine - Colon • No digestion occurs here • Water is absorbed from remaining food • Bacteria feed on material passing through and produce vitamins vital to our health • Waste material, feces, is prepared for elimination from the body. It is stored in the rectum until it leaves the body through the anus. The End! Where will I go? www.youtube.com/watch?v=OYWVbt6t2mw Let’s Digest Something! http://kitses.com/animation/swfs/digestion.swf