Digestive System

Digestive System a coiled, muscular tube (6-9 meters long) beginning with the mouth and ending with the anus 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 Mouth Esophagus Stomach Small intestine Large intestine Rectum Helpers are: liver, gall bladder & pancreas

process by which food is converted into soluble forms Digestion process by which food is converted into soluble forms 2 forms of digestion physical or mechanical chemical

Forms of Digestion Physical Digestion Chemical Digestion  mechanical breakdown of food into smaller particles  chemical breakdown of food by enzymes  begins in mouth by chewing – teeth and tongue  begins in mouth with saliva  increases surface area of food  mostly occurs in small intestine

Physical Digestion Chemical Digestion  mechanical  chemical  begins in mouth by chewing  begins in mouth with saliva

Stages of Digestion      movement propels food through system secretion release of digestive juices  digestion breakdown of food into molecular sizes food molecules passing through intestinal walls  absorption elimination  removal of undigested food

Primary Digestive Organs

begin the mechanical breakdown of food teeth mouth tongue - transports food to stomach through the process of peristalsis esophagus - muscular organ that stores, mixes, digests and controls passage of food stomach

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

Peristalsis series of involuntary muscular contractions in the esophagus that squeeze the food down to the stomach esophagus food stomach

From the esophagus to the Stomach Click on picture to show video http://www.gastrointestinalatlas.com

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

- coiled tube from 3 - 6m long, the major site for digestion and absorption of nutrients; contain villi small intestines - 1.5 m long tube, absorbs water from undigested material large intestines - opening for removal of feces anus

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

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

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

Accessory Digestive Organs

salivary glands - secrete a chemical (enzyme) that breaks down starch into glucose liver - produces bile, which helps break down fats in small intestines gall bladder - stores bile pancreas - secretes enzymes that break down starches and proteins

The Liver (& Gall Bladder) Liver produces bile to help with chemical digestion Bile stored in the gall bladder (then sent to beginning of small intestine) The liver filters harmful substances or wastes, turning some of the waste into more bile 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.

Accessory Digestive Organs connected to stomach by ducts liver gall bladder pancreas

Pancreas Produces some digestive enzymes

Digestive Disorders

spot in stomach lining where cells are destroyed, lining unprotected, irritated by stomach acid ulcers gastritis swelling of stomach lining, caused by irritating foods, alcohol, or bacteria acid reflux "back washing" of acid from the stomach into the esophagus; also called heartburn

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 – fats, proteins, and carbs. Large intestine – bacteria help with final stage of digestion

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

Review

1. 2. 3. 4. 5. 6. 7. 8. 9. 10.

1. mouth 1. 2. esophagus 2. 3. 3. stomach 4. 4. small intestine 5. 5. large intestine 6. anus 6.

salivary glands 1. liver 2. gall bladder 3. pancreas 4.

1. 2. 3. 4. 5. 6.

1. 2. 3. 4.

Match the structure with the number.    liver small intestine salivary glands pancreas large intestine gall bladder esophagus stomach anus      

         Match the function with the number. major organ for digestion and absorption of nutrients contains enzymes for the first chemical breakdown of food  transports food by peristalsis stores undigestible food secretes enzymes for starch breakdown mixes and stores food the 4 accessory digestive organs stores bile produces bile contains villi      