Your Digestive System The main role of the digestive system is to break down and absorb nutrients that are necessary for growth and maintenance.

The Path of Digestion n Mouth n Esophagus n Stomach n Small intestine n Large intestine n Rectum n Helpers are: liver, gall bladder & pancreas

Beginning in the Mouth n Mechanical Digestion begins: –Chewed by the mouth using teeth and tongue –Food is swallowed & squeezed through the esophagus to the stomach –Churned by stomach muscles

Swallowed food enters the Esophagus

Esophagus n Moves food from the back of throat to the stomach n Epiglottis – flap of skin that covers windpipe (trachea), keeping food out of lungs n Valve at the end of the esophagus (sphincter) allows food to pass into the stomach but not back into the esophagus n Takes 8-10 seconds to move bolus (chewed food) from swallowing to stomach

From the esophagus to the Stomach Click on picture to show video

Stomach n Muscular walls of stomach contract to churn and mix the food with gastric juices n Gastric juices (hydrochloric acid and pepsin with mucus) - begin the break down of proteins n Chemical and mechanical digestion takes about 2 to 3 hours n Mixture of partially digested food is called chyme

Food passes through the pyloric valve from the stomach to the small intestines Close-up of pylorus (pyloric valve) The small intestine is 22 feet long

Small Intestine n Chyme is flooded with enzymes n Enzymes help break down the nutrients to basic forms n Liver produces bile (stored in the gall bladder) – a salt that helps break down fats n Villi - finger like projections in the wall of the small intestines where blood vessels absorb nutrients into the bloodstream

From the small intestine food passes through a valve to the large intestine Click on picture to show video clip

Large Intestine n Undigested material (fiber, water, and un-digestible substances) moves into the large intestine or colon n Water is removed and undigested material reduced to a solid waste called feces n Colon contains bacteria to help final digestion n Feces (yes, poop) is stored in the rectum and eliminated

Elimination n Undigested waste is moved into the rectum where it is eliminated through the anus n Peristalsis – the muscular contractions that move food through your digestive system

The Liver (& Gall Bladder) n Liver produces bile to help with chemical digestion n Bile stored in the gall bladder (then sent to beginning of small intestine) n The liver filters harmful substances or wastes, turning some of the waste into more bile n The liver helps figure out how many nutrients will go to the rest of the body, and how many will stay behind in storage. – For example, the liver stores certain vitamins and a type of sugar your body uses for energy.

Pancreas n Produces some digestive enzymes

Chemical Digestion  Mouth - chemical digestion begins in the mouth with saliva (spit)  Stomach - gastric juices (stomach acid, mucus, enzymes) begin to break down the food to smaller molecules  Small intestine – food broken down even more so your body can absorb the nutrients ** Most digestion occurs in the small intestine  Large intestine – bacteria help with final stage of digestion

Nutrients n Carbohydrates: starches and sugars n Proteins: simplest form is amino acids n Fats : absorbed as fatty acids (with the help of bile from the liver) n Vitamins & Minerals n Water

Enzymes  Enzymes are proteins that help chemical digestion  Enzymes help a chemical reaction without being changed itself  Found in raw fruits and vegetables  Also produced in the stomach, small intestine and pancreas

Click here to link to KidsHealth flash player of digestive system. Click here to link to animation of food being swallowed