Unit 7 – Nutrition THE DIGESTIVE SYSTEM

Discussion…  What do you remember about digestion from 7 th grade?  What vital organs are a part of digestion?  What substances are involved in the process?

Video Overview of Digestion 

Understanding Digestion  Definition : The digestive system is a group of organs working together to convert food into energy and basic nutrients to feed the entire body.

Parts of the Digestive System  Gastrointestinal Tract (GI Tract) –  A.K.A. alimentary canal  Made up of the oral cavity, pharynx, esophagus, stomach, small intestines and large intestines.

The Process of Digestion  Begins the process at the mouth (a.k.a. the oral cavity).  Accessory Organs in the Mouth:  The tongue, teeth, and salivary glands  Process: 1. The teeth break food into small pieces. 2. The salivary glands secrete saliva to moisten the food.  Saliva helps moisten food which begins the digestion of carbohydrates and to lubricate the food as it passes through the mouth, pharynx and esophagus. 3. The tongue and other muscles push the food into the pharynx.

Digestive Process Continued  The food enters the pharynx (A.K.A. the throat).  The pharynx is responsible for the passing of masses of chewed food from the mouth to the esophagus.  The pharynx is also responsible for the passage of air in our respiratory system.  The epiglottis is a tissue flap that directs food to the esophagus and air to the lungs.

Digestive Process Continued  From the pharynx the food moves into the esophagus which connects to the stomach.  Food is then trapped in the stomach by a close at the end of the esophagus.

Digestive Process Continued  The stomach is a muscular sac and in an average person is about the size of two fists placed next to each other.  The purpose of the stomach is to store food so that the body has time to properly digest large meals.  It contains digestive enzymes and hydrochloric acid which continues the digestive process.

Digestive Process Continued  Once the food leaves the stomach it enters the small intestine which takes up most of the space in the abdominal cavity.  The small intestine has multiple folds which maximize the digestion of food and absorption of nutrients.  At the end of the small intestine about 90% of the nutrients have been extracted from the food.

Final Stage  The final stage of the digestive process is the large intestine.  The large intestine absorbs water and contains bacteria that aids in the breaking down of wastes to extract some small amounts of nutrients.

Assist in the Digestive Process  1. Epiglottis – A tissue flap that directs food to the esophagus and air to the lungs.

Glands that Assist in the Digestive Process 1. The Liver – Weighs about 3 lbs making it the second largest organ in the body. The main function of the liver in digestion is the production of bile which it secretes into the small intestine.

Glands that Assist in the Digestive Process 2. The Gallbladder – Used to store and recycle excess bile from the small intestine so that it can be reused.

Glands that Assist in the Digestive Process 3. Pancreas – Secretes digestive enzymes into the small intestines to complete the chemical digestion of food.