I. Introduction to the Digestive System - The digestive system is made up of all of the organs in our body in charge of breaking down food. -The digestive system has 3 jobs: 1. Breaks down food into smaller molecules our cells can use. 2. Absorbs nutrients into our circulatory system (bloodstream). 3. Eliminates waste products.
II. What happens when we eat? -Food enters the digestive system where it is broken down into simpler molecules that can move from the digestive system to the circulatory system (the blood). After the nutrients move into the blood, they can be taken to the rest of your body to feed your body’s cells.
III. Two kinds of Digestion 1. Mechanical digestion is the physical process of breaking food down into smaller pieces. 2. Chemical digestion is the process of changing food on a molecular level. This change happens because of the action of enzymes in your digestive system.
IV. Steps of Digestion Step 1: Food is ingested (put in your mouth) and you chew. The teeth help breakdown the food into smaller pieces. Chewing is a form of mechanical digestion.
Your Mouth Incisors Gums Soft palate Tonsils Opening of salivary gland duct Cuspids or canines Bicuspids or premolars Molars Tongue Teeth Uvula Hard palate
IV. Steps of Digestion Step 2: Chemical digestion now begins in your mouth. Salivary glands in your mouth secrete saliva. Saliva contains a digestive enzyme called amylase, which breaks down sugars. Salivary gland Salivary ducts Salivary glands Tongue
IV. Steps of Digestion Step 3: Once food is chewed, the food is swallowed. Swallowing forces food from the mouth into the throat, food then moves from the mouth into the esophagus. The esophagus is the muscular tube that connects the mouth to the stomach.
IV. Steps of Digestion Step 4: Food moves down the esophagus by peristalsis. Peristalsis is a series of involuntary, smooth muscle contractions along the walls of the digestive tract which force the food to move down the digestive tract.
IV. Steps of Digestion Step 5: Peristalsis pushes food down the esophagus into the stomach – the muscular, pouch-like structure in the digestive tract. Both mechanical and chemical digestion taken place in the stomach. Mechanical Digestion: Walls of the stomach contract to mix food. Chemical Digestion: Glands in the stomach wall secrete gastric juices made up of hydrochloric acid (HCl) and the enzyme pepsin which break down food.
IV. Steps of Digestion Step 6: After 2-4 hours the food has been liquidated and peristalsis pushes the food into the small intestine. Food digestion is completed in the first half of the small intestine through mechanical and chemical digestion. Mechanical Digestion: Muscles in the small intestine contract to break down food. Chemical Digestion: The pancreas and liver secrete enzymes that break down the food even more.
VI. After the food is digested, how is it absorbed? - -Digested food moves through the rest of the small intestine and passes over thousands of villi - tiny, fingerlike projections that help absorb digested food. Villi are the connection between the digestive and circulatory system. -The food moves directly from the small intestine to the bloodstream where it travels to your cells and feeds them.
VI. After the food is digested, how is it absorbed? The villi are the link between the digestive system and the circulatory system. Columnar epithelium Lymph vessel Blood vessel network Fatty acids Amino acids Monosaccharides
VII. After food is absorbed, how are waste products eliminated? - -Material that can’t be digested in the small intestine passes into the large intestine which is also called the colon. The walls of the large intestine absorb water and salts from the leftover waste. -The left over waste product, called feces, enters the rectum and is eliminated (removed) from our body through the anus. Large intestine Rectum Anus