The digestive system is made up of the digestive tract—a series of hollow organs joined in a long, twisting tube from the mouth to the anus—and other organs that help the body break down and absorb food. Organs that make up the digestive tract are the mouth, esophagus, stomach, small intestine, large intestine—also called the colon—rectum, and anus. Inside these hollow organs is a lining called the mucosa. In the mouth, stomach, and small intestine, the mucosa contain tiny glands that produce chemicals called enzymes and acids to help digest food. The digestive tract also contains a layer of smooth muscle that contracts to help break down food and move it along the digestive tract.
1.What is the primary function of the digestive system? The function of the digestive system is to break down food. 2. What is the function of the mouth? The mouth breaks down food into smaller pieces and secretes enzymes that begin digestion. 3. What is the function of the esophagus? The esophagus transport food and water to the stomach. 4. What are the two primary types of digestive chemicals produced by the digestive system? Acids (particularly hydrochloric acid) and enzymes.
Three “solid” digestive organs, the gall bladder, liver, and the pancreas, produce digestive chemicals that reach the intestine through small tubes called ducts. The gallbladder stores a fat digesting enzyme called bile until it is needed in the intestine.
Mechanical Digestion 1.Mechanical digestion is the process of breaking food up into smaller pieces. Mechanical digestion takes place first in the mouth from chewing. 2.The smooth muscles in the stomach and small intestines continue to mix and churn the food as it mixes with the digestive juices to make it break down even further. Muscular contractions move the digested food the length of the small intestine. The remaining waste is moved along the length of the large intestine where it is ultimately expelled as waste. Chewing animation http://www.youtube.com/watch?v=9LcIoYEe52Y Mechanical digestion in stomach (mute this.) http://www.youtube.com/watch?v=URHBBE3RKEs
Chemical Digestion 1.Chemical digestion also occurs in the mouth (salivary glands) and in the stomach and small intestines. Enzymes and acids are produced in the mouth, stomach, and small intestines. The stomach and small intestine are lined with a special layer of tissue called mucosa that helps keep the acidic digestive juice from dissolving the tissue of the stomach itself. (show animation through to stomach.) 2.The liver, gall bladder, and the pancreas also provide digestive chemicals. These digestive juices break or dissolve food down into the basic elements which can then pass into the blood vessels surrounding the small intestine. YouTube chemical digestion tutorial (some higher level vocabulary.) http://www.youtube.com/watch?v=qyJx_UVEgQI&feature=related
5. The liver, gall bladder, and pancreas have a similar digestive function. How do these organs contribute to digestion? Each produces or distributes some type of digestive chemical. 6. Breaking food into smaller pieces by chewing and the muscular contractions of the stomach and small intestine to further break food into smaller particles are examples of what type of digestion? Mechanical. 7. The action of digestive chemicals to dissolve food into microscopic particles that can be absorbed into the blood stream. Chemical digestion. 8. Why does the hydrochloric acid produced by the stomach not destroy the lining of the stomach and small intestine? The lining of these structures is protected by a special layer of tissue.
The majority of the digestion takes place in the small intestine not the stomach. As the food particles continue through the small intestine, they eventually are broken down into microscopic particles that can be absorbed into the thousands of miles of capillaries lining the small intestine.
Starches/carbohydrates from grains and root vegetables like potatoes is broken down into glucose. Proteins form meat, dairy, fish, eggs, and some vegetables like beans is broken down into the building blocks of proteins, amino acids. Fats are broken down into fatty acids, which have an important role in nearly every function of our body.
The job of the large intestine is to absorb water from the remaining indigestible food material and then to pass this useless waste material (feces) from the body through the rectum.
While the liver has only a minor role in digestion, it is thought to have over 500 total functions, more than any other organ except the brain.
9. Starches/carbohydrates from foods like_______________________________are broken down into ____________________________. 10. Proteins are broken down into ______________________________________, which can then be reassembled by our bodies to make our own proteins. 11. Fats are broken down into ____________________________________________. 12. In which organ does the majority of digestion occur? 13. The majority of digested nutrients enter our bloodstream through special channels lining the ___________________, rather than the stomach. 14. What are the two primary roles of the large intestine? The main functions of the colon are to reabsorb excess water and move solid waste from the body. glucose grains, pasta, root vegetables amino acids fatty acids Small intestine
Other important jobs of the liver include: Filtering toxins from our blood before they get out into the body Maintain a proper level of glucose (sugar) in our blood Stores certain vitamins and minerals Removes waste materials that result from digestion and the normal breakdown of the cells in our bodies. All the blood leaving the stomach and intestines passes through the liver. Produces certain proteins necessary for making plasma Production of cholesterol and special proteins to help carry fats through the body Converts excess glucose into a substance called glycogen, a form of stored energy that can be converted back into glucose when the body needs it. Stores iron which is needed for the hemoglobin of blood Produces substances that help the body develop amino acids which are the building blocks of protein Regulates blood clotting Converts ammonia, a poisonous waste product of cellular activity, into urea (a component of urine)
Common Diseases of the Digestive System All parts of the digestive and excretory system are prone to cancer, though cancer of the colon is one of the most common.
Ulcer- an ulcer is a hole in the mucosal lining of the stomach or small intestine. If serious enough, an ulcer can cause internal bleeding.
Acid Reflux- a medical condition where stomach acids rise or leak up from the stomach into the lower part of the esophagus. These powerful acids damage the tissue of the esophagus and can result in permanent, long-term damage.
Crohn’s Disease- an inflammatory disease of the digestive system that can occur anywhere in the digestive tract from the stomach to the rectum. Symptoms include vomiting, severe abdominal pain, bloody diarrhea, and weight loss.
Cirrhosis- a type of chronic liver disease characterized by the development of small nodules throughout the liver and gradual replacement of healthy liver tissue with scar tissue (which cannot carry out the function of the liver.) Cirrhosis is most commonly caused by alcoholism, Hepatitis B and C, and fatty liver disease.
Gall Stones -small, pebble-like substances that develop in the gall bladder.
15. The most common form of digestive system cancer occurs in which digestive organ? The colon (large intestine.) 16. This digestive disorder is characterized by a backflow of stomach acid and partially digested food from the stomach upward into the esophagus. Acid reflux. 17. Which substances in our food will would a person have difficulty digesting if he or she suffered from gall stones? The gall bladder stores and releases bile into the small intestine. Bile breaks down fats.