THE DIGESTIVE SYSTEM THE FOUR STEPS OF DIGESTION

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1 THE DIGESTIVE SYSTEM WHAT IS THE DIGESTIVE SYSTEM? the digestive system is a long, muscular tube The entire system is approximately 9m in length and is usually a one way tract WHY DO WE NEED A DIGESTIVE SYSTEM? our body cannot readily use food some foods are too large and not water soluble the digestive system breaks down the food we eat into small pieces that can be metabolized (used for energy) by individual cells in our body we must eat foods that contain nutrients (carbohydrates, lipids, proteins, vitamins, minerals, water) so our body can function and provide us with the energy we need THE FOUR STEPS OF DIGESTION 1. INGESTION - the taking in of nutrients 2. DIGESTION - mechanical breakdown of food - Chemical breakdown of food 3. ABSORPTION - the taking up of digested molecules into the cells of the digestive tract where they enter our bloodstream on their way to each of our body s cells. 4. ELIMINATION - waste products of the digestive process are eliminated from the body 1

2 Mouth The Digestive System Esophagus Liver Gall Bladder Duodenum Ascending Colon Ileum Cecum Appendix Anus Stomach Pancreas Transverse Colon Descending Colon Jejunum Sigmoid Colon Rectum 1. Mouth PARTS AND FUNCTIONS the first part of the digestive system where food enters the body Chewing and salivary enzymes in the mouth are the beginning of the digestive process (breaking down the food 2. Esophagus the long tube between the mouth and the stomach. It uses rhythmic muscle movements (called peristalsis) to force food from the throat into the stomach. 3. Stomach a sack-like, muscular organ that is attached to the esophagus. when food enters the stomach, it is churned in an acid bath 2

3 4. Duodenum the first part of the small intestine; it is C-shaped and runs from the stomach to the jejunum. 5. Jejunum the long, coiled mid-section of the small intestine; it is between the duodenum and the ileum. 6. Ileum the last part of the small intestine before the large intestine begins. 7. Cecum the first part of the large intestine; the appendix is connected to the cecum. 8. Ascending colon the part of the large intestine that run upwards; it is located after the cecum. 9. Transverse colon the part of the large intestine that runs horizontally across the abdomen. 10. Descending colon the part of the large intestine that run downwards after the transverse colon and before the sigmoid colon. 3

4 11. Sigmoid colon the part of the large intestine between the descending colon and the rectum. 12. Rectum the lower part of the large intestine, where feces are stored before they are excreted. 13. Anus the opening at the end of the digestive system from which feces (waste) exits the body. Gall Bladder DIGESTIVE SYSTEM ORGANS a small, sac-like organ located by the duodenum. It stores and releases bile (a digestive chemical which is produced in the liver) into the small intestine. Liver a large organ located above and in front of the stomach. It filters toxins from the blood, and makes bile (which breaks down fats) and some blood proteins. Pancreas an enzyme-producing gland located below the stomach and above the intestines. Enzymes from the pancreas help in the digestion of carbohydrates, fats and proteins in the small intestine. Appendix a small sac located on the cecum 4

5 PARTS AND FUNCTIONS - the opening at the end of the digestive system from which feces (waste) exits the body. - a small sac located on the cecum. - the part of the large intestine that run upwards; it is located after the cecum. - the first part of the large intestine; the appendix is connected to the cecum. - the part of the large intestine that run downwards after the transverse colon and before the sigmoid colon. - the first part of the small intestine; it is C-shaped and runs from the stomach to the j ejunum. - the long tube between the mouth and the stomach. It uses rhythmic muscle movements (called peristalsis) to force food from the throat into the stomach. - a small, sac-like organ located by the duodenum. It stores and releases bile (a digestive chemical which is produced in the liver) into the small intestine. - the last part of the small intestine before the large intestine begins. - the long, coiled mid-section of the small intestine; it is between the duodenum and the ileum. - a large organ located above and in front of the stomach. It filters toxins from the blood, and makes bile (which breaks down fats) and some blood proteins. - the first part of the digestive system, where food enters the body. Chewing and salivary enzymes in the mouth are the beginning of the digestive process (breaking down the food). - an enzyme-producing gland located below the stomach and above the intestines. Enzyme from the pancreas help in the digestion of carbohydrates, fats and proteins in the small intestine. - the lower part of the large intestine, where feces are stored before they are excreted. - the part of the large intestine between the descending colon and the rectum. - a sack-like, muscular organ that is attached to the esophagus. When food enters the stomach, it is churned in an acid bath. - the part of the large intestine that runs horizontally across the abdomen. WHAT IS PERISTALSIS? Rythmic contractions of the muscle layers INDEPENDENT OF GRAVITY, that s why you can drink water standing on your head! A MODEL OF PERISTALSIS 5

6 Materials old nylon stocking; cut off both ends (tube-like) an orange Instructions: take the orange and attempt to pass the orange from one end of the nylon tube to the other Analysis Questions: How is this model similar to peristalsis? What kinds of things do you have to do to keep the orange moving through the nylon tube? Homework!! 1. Read pp Questions 3,4,5, pg 82 6