The Digestive System 7th Grade Life Science

Three Major Functions of the Digestive System Break down ingested food Put nutrients into the bloodstream for delivery to the cells.... glucose will be used to make ATP energy and amino acids will be used to make proteins. 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 these organs? B. C. D. E. Food never touches the accessory organs!

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! https://www.youtube.com/watch?v=_QYwscALNng Great National Geographic video Where will I go? www.youtube.com/watch?v=OYWVbt6t2mw Let’s Digest Something! http://kitses.com/animation/swfs/digestion.swf