Understanding Digestion

Knowing the proper foods to eat, the appropriate amounts of vitamins and minerals, and having awareness of healthy weight and calorie intake are important parts of understanding nutritional concepts, but what about what happens with all these things once they are in your body. This is where a healthy digestive system comes in, and knowing how it works may help us understand it's importance. 

http://www.niddk.nih.gov/health-information/health-topics/Anatomy/your-digestive-system/Pages/anatomy.aspx

Digestion starts immediately when you put a piece of food in your mouth. Your teeth and saliva work together to begin the process of proper digestion. Each type of macro-nutrient is digested differently and have different processes in each part of the digestive system. Carbohydrates begin the process in the mouth, where saliva enzymes begin the digestion process. Also in the mouth, the tongue begins to release a fat-digesting enzyme and starts the process on fatty foods. For proteins,  the mouth only plays the role of crushing and softening foods. All foods than travel down the esophagus into the stomach. In the stomach "digestion of starch continues in the upper stomach...in the lower digesting area of the stomach, hydrochloric acid and an enzyme in the stomach's juices halt starch digestion" (Sizer & Whitney, 2013). Very little of the fats are digested in the stomach and the fats are usually last to leave this part of the system. The stomach releases a protein digesting enzyme at this point that beings to break down the protein chains into smaller chains, The next part of the process takes place in the small intestine as well as the liver, pancreas, and gallbladder. Carbohydrates are broken down more in this stage by an enzyme produced by the pancreas. Sugars and starches are finally broken down completely into simple sugars by enzymes  lining the stomach and are absorbed (Sizer & Whitney, 2013). Fats are emulsified in this stage by the bile that is produced by the liver and stored in the gallbladder. Fat digesting enzymes are then released by the pancreas splitting the fats into component parts and is then absorbed. (Sizer & Whitney, 2013). In the small intestine proteins are broke down into amino acids and most of them are adsorbed. The final stage before deification takes place in the large intestine. In this final stage any remaining carbohydrates that remain are broke down by bacteria, any fats that were not absorbed are removed as waste from the body, and the same happens for any proteins that were not digested. All final waste is removed out the rectum in the final part of digestion. 

Reference:

Sizer, F. & Whitney, E. (2013).  Nutrition: Concepts and Controversies (13th ed.).  Mason, OH: Cengage Learning.

U.S. Department of Health and Human Services. (2013). Your Digestive System and How It Works. Retrieved from http://www.niddk.nih.gov/health-information/health-topics/Anatomy/your-digestive-system/Pages/anatomy.aspx