2.2 The Digestive and Excretory Systems Nutrients are substances the body requires for energy, growth, development, repair, or maintenance. We get nutrients from what we eat and drink. Four Food Groups Grain products Vegetables and fruit Milk products Meat and alternatives See pages 64 - 65 (c) McGraw Hill Ryerson 2007

Types of Nutrients Carbohydrates Proteins The bodies quickest source of energy Examples include: rice, vegetables, cereal, and bread Proteins Used to build parts of your bodies muscles, skin, hair, and nails Examples include: fish, meat, eggs, nuts, soy products See pages 66 - 69 (c) McGraw Hill Ryerson 2007

Types of Nutrients Fats Minerals and Vitamins Used to build cell membranes and can be stored for future energy. Examples include: butter, vegetable oil, and meat Minerals and Vitamins Needed in small amounts to perform various body functions Two common minerals and vitamins are calcium and vitamin D Water is not a nutrient but is necessary for life! See pages 66 - 69 (c) McGraw Hill Ryerson 2007

The Four Stages of Digestion The process in which food is broken down, nutrients are absorbed, and wastes eliminated is called digestion and occurs in the digestive system. The fours stages of digestion are: Ingesting Digesting Absorbing Eliminating See page 70 (c) McGraw Hill Ryerson 2007

Stage 1: Ingesting Ingesting, or ingestion, means to bring food into the body. This is the starting point of the digestive process. See page 71 (c) McGraw Hill Ryerson 2007

Each small piece of food is called bolus. Stage 2: Digesting The Mouth Mechanical digestion occurs when your teeth and tongue break food into small enough pieces to swallow. Each small piece of food is called bolus. Chemical digestion occurs when saliva begins to break down the bolus. An enzyme in your saliva begins to break down simple and complex carbohydrates. See page 71 (c) McGraw Hill Ryerson 2007

When you swallow, your food enters the esophagus. Stage 2: Digesting The Esophagus When you swallow, your food enters the esophagus. The esophagus is a long muscular tube that carries food to your stomach. The bolus is pushed through the esophagus in a process called peristalsis. (c) McGraw Hill Ryerson 2007 See page 72

Inside the stomach is gastric juice, which is very acidic. Stage 2: Digesting The Stomach Inside the stomach is gastric juice, which is very acidic. The stomach walls are lined with mucus to protect the tissue from being damaged by the acid. An enzyme called pepsin, present in gastric juice, breaks down protein. The bolus that enters your stomach breaks down into a liquid called chyme. See page 73 (c) McGraw Hill Ryerson 2007

The first metre of the small intestine is called the duodenum. Stage 2: Digesting The Small Intestine The first metre of the small intestine is called the duodenum. The pancreas adds enzymes that help break down the carbohydrates, protein, and fat in the chyme. The liver produces bile which is stored in the gall bladder. Bile breaks the globs of fat into smaller droplets. See page 74 (c) McGraw Hill Ryerson 2007

The Small and Large Intestine Stage 3: Absorbing The Small and Large Intestine Absorption is the process in which nutrients and water are absorbed by the small and large intestine. The small intestine is covered with villi to help increase the rate at which nutrients are absorbed. The large intestine absorbs water and some minerals. See page 75 (c) McGraw Hill Ryerson 2007

Liquid and gas wastes are removed by your excretory system. Stage 4: Eliminating Any solid material, undigested by the end of the large intestine is called feces. Feces are stored in the rectum until they are eliminated through the anus. Liquid and gas wastes are removed by your excretory system. The main organs in your excretory system are your kidneys and your bladder. See page 76 (c) McGraw Hill Ryerson 2007

Eating Disorders Anorexia nervosa is a disorder when a person severely restricts what they eat. Bulimia nervosa is a disorder when a person eats large amounts of food and then vomits or takes laxatives to get rid of the food before it is completely digested. See page 77 Take the Section 2.2 Quiz (c) McGraw Hill Ryerson 2007