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