Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Digestion
Transcript
The Digestive System Grade 9 Biology Ms. Marcos Moving into human body systems! What does your digestive system look like? The tube starts here: And although there are a few twists and turns along the way… It comes out here: Anything that goes in the top hole (mouth) does not become part of the body until it is broken down then absorbed though a series of specialized structures. A Tour of the Digestive System Mouth ◦ Roles in digestion and other body processes ◦ Tongue, teeth, salivary glands, pharynx ◦ Enzymes Esophagus ◦ Peristalsis Stomach ◦ Enzyme action ◦ Cardiac and pyloric sphincters and stomach cell types Pancreas ◦ Digestion enzymes, pH balance and maintenance of blood sugar Large intestine ◦ Functions and anaerobic bacteria within ◦ Enzymes and gastric secretions Small intestine ◦ Specialization – structure and function three sections and of the villi ◦ Epiglottis and choking Liver / Gall bladder Rectum and Anus ◦ Expulsion of wastes What does the digestive system do? DIGESTION: ◦ Mechanical vs. chemical digestion Mechanical is breaking the food into smaller pieces Chemical is using enzymes and chemical reactions to break apart the molecule ABSORPTION: ◦ Moving the broken down food into the blood or the lymph to be carried around the body ELIMINATION: ◦ Getting rid of anything that you can’t digest The parts of the digestive system… Mouth Tongue Salivary glands Oral cavity Pharynx Esophagus Stomach Pyloric sphincter Liver Gall-bladder Pancreas Small intestine Large intestine Anus Rectum Many parts work together and are coordinated by hormones. A Tour of the Digestive System Mouth ◦ Roles in digestion and other body processes ◦ Tongue, teeth, salivary glands, pharynx ◦ Enzymes Esophagus ◦ Peristalsis Stomach ◦ Enzyme action ◦ Cardiac and pyloric sphincters and stomach cell types Pancreas ◦ Digestion enzymes, pH balance and maintenance of blood sugar Large intestine ◦ Functions and anaerobic bacteria within ◦ Enzymes and gastric secretions Small intestine ◦ Specialization – structure and function three sections and of the villi ◦ Epiglottis and choking Liver / Gall bladder Rectum and Anus ◦ Expulsion of wastes The Mouth – Where digestion begins Hard palate (the bony part at the top) Soft palate composed of muscle tissue ◦ The uvula - the thing that hangs down in the back of your throat It stops liquid or food from coming out your nose when you swallow Tongue – moves around the food and forms a bolus (a ball of food) Types of teeth There are different types of teeth for different functions: Sharp pointed teeth for cutting and tearing food Grinding and mashing food Crushing and grinding food Cutting and chopping food What’s in saliva and what does it do? Water Makes food soft Mucus Helps food slide down the esophagus Bicarbonate ions neutralize acid produced by bacteria (helps prevent tooth decay) Salivary amylase breaks down starch in the presence of water Starch maltose (a disaccharide of glucose) How much saliva do you produce in a day? About 1-2 litres! A Tour of the Digestive System Mouth ◦ Roles in digestion and other body processes ◦ Tongue, teeth, salivary glands, pharynx ◦ Enzymes Esophagus ◦ Peristalsis Stomach ◦ Enzyme action ◦ Cardiac and pyloric sphincters and stomach cell types Pancreas ◦ Digestion enzymes, pH balance and maintenance of blood sugar Large intestine ◦ Functions and anaerobic bacteria within ◦ Enzymes and gastric secretions Small intestine ◦ Specialization – structure and function three sections and of the villi ◦ Epiglottis and choking Liver / Gall bladder Rectum and Anus ◦ Expulsion of wastes Traveling to the stomach… Esophagus ◦ Tube from pharynx to stomach ◦ It has: Mucus membranes Helps the food slide down Muscle Pushes the food down the tube Food moves down by peristalsis Peristalsis (and reverse peristalsis) How long does peristalsis take? ◦ About 9 seconds from pharynx to stomach (rate of 2-4cm/s) Swallowing Animation Swallowing… The bolus enters the PHARYNX 1. Uvula moves back to cover openings to nose 2. Trachea (to the lungs) moves up 3. Epiglottis covers the trachea (so that you don`t choke!) 4. Food goes down by peristalsis Swallowing in action… Reaching the stomach… Bolus arrives at the cardiac sphincter ◦ This is the “door” at the top of the stomach ◦ Made of muscle What is heartburn and what causes it? Opening of the cardiac sphincter allowing food (soaked in stomach acid) to enter the esophagus. http://www.youtube.com/watch?v=1ZIK6Ua20JA A Tour of the Digestive System Mouth ◦ Roles in digestion and other body processes ◦ Tongue, teeth, salivary glands, pharynx ◦ Enzymes Esophagus ◦ Peristalsis Stomach ◦ Enzyme action ◦ Cardiac and pyloric sphincters and stomach cell types Pancreas ◦ Digestion enzymes, pH balance and maintenance of blood sugar Large intestine ◦ Functions and anaerobic bacteria within ◦ Enzymes and gastric secretions Small intestine ◦ Specialization – structure and function three sections and of the villi ◦ Epiglottis and choking Liver / Gall bladder Rectum and Anus ◦ Expulsion of wastes The Stomach How big is your stomach? ◦ About 1.5 to 2L in an adult human (300L in a cow!) This is a rabbit stomach The Stomach J-shaped organ Three layers of muscle ◦ Mix up and break up the food Gastric glands make gastric juice Gastric juice has: ◦ Pepsinogen + Hydrochloric acid Pepsin PEPSIN an enzyme it breaks down proteins into peptides (small protein sections) Within the walls of the stomach… Pepsinogen Pepsin HCl (Activates more Pepsinogen) Gastric gland Mucus cell (shown in red) Parietal Cell Peptic cell 3 types of cells in the stomach: ◦ Mucus cells Mucus protects the stomach ◦ Parietal cells Secrete acid (HCl at pH 3) kills bacteria and helps break food down ◦ Peptic cells Secrete pepsinogen to make pepsin Why doesn’t the stomach digest itself? HCl could eat through the stomach Stopped by the mucus layer Pepsin could digest protein in the stomach cells Pepsin is only made when pepsinogen mixes with HCl Stopped by the mucus layer When things go wrong… Bacterial infections ◦ Cells can’t make mucus ◦ Can cause ulcers and stomach cancer http://www.youtube.com/watch?v=1ZIK6Ua20JA&feature=channel_page How long does food stay in your stomach? ◦ 2 - 6 hours Chyme = liquid food that leaves your stomach Enters the small intestine controlled by the PYLORIC SPHINCTER “Door” of muscle at the bottom of the stomach Digestion Questions #1: 1. Explain the step by step process that occurs when a. someone chokes on a piece of food. What goes wrong? (1) b. you are drinking water and accidentally laugh, causing the water to come out of your nose. What goes wrong? (1) 2. Explain all the types of digestion that occur in the mouth. (2) 3. What possible problem could lead to an esophageal ulcer? Explain what would happen to cause this. (2) 4. Explain all the types of digestion that occur in the stomach. (2) 5. If someone had a severe ulcer, would it be possible to remove his or her stomach and replace it with a bag? What properties would this bag need to have in order to function? How would that person’s diet need to change? (3)
