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Ch 2-2 The Digestive and Excretory Systems (redirected from Ch 2-2 The Digestive and Excretory Systems)

Page history last edited by PBworks 11 years, 11 months ago

Chapter 2.2 - The Digestive and Excretory Systems

 

 

 The Four Food Groups

 

  • Grain products
  • Vegetables and Fruit
  • Milk products
  • Meats and Alternatives

 

Note: It is important to make sure your diet includes all of these four food groups. 

 

Types of Nutrients

 

Carbohydrates - These are the bodies quickest source of energy. There are two types of carbohydrates: Simple and Complex. A simple carbohydrates is just one molecule of sugar.

                           A complex carbohydrate is a chain of simple carbohydrates joined together. Foods such as pasta, brown rice, and whole grain cereals contain complex carbohydrates.

 

Proteins - These help build your body's muscle, skin, hair, and nails and are also used in various chemical reactions within your body. Fish, nuts, poultry, soy, and dairy products are rich in proteins.

 

Fats - These build cell membranes and can be stored by the body for future energy uses. There are two types of fats: UNSATURATED fat, and SATURATED fat. Unsaturated fat is "good fat" and comes from fruits, vegetables, and fish. Saturated fats are solid at room  temperature.

 

Minerals and Vitamins - They help the body perform various functions. Two common vitamins and minerals are calcium and vitamin D. You can get vitamin D from going out in the sunlight.

 

Fun Fact: Although water is not a nutrient, it is necessary for life. Water transports nutrients and waste and is also necessary for chemical reactions and for cooling the body through sweat or perspiration.

 

The Four Stages of Digestion

 

1) Ingesting - This is the starting point of the digestion process. It begins when you take a bite of food or a sip of a liquid.

 

2) Digesting - First the food undergoes mechanical digestion inside your mouth when you chew. The food is broken down into small pieces called a bolus. Then the food passes through the pharynx. This is when your airway passage and the rest of your digestive system meet. The bolus continues into the esophagus where it is pushed along by peristalsis. Peristalsis is like using your hands to push a marble down a smalll rubber tube. Then the bolus enters the stomach and into the gastric juice. The bolus is broken down into a liquid called chyme. The chyme then leaves the stomach and is emptied into the small intestine. The first part of the intestine is called the duodenum. The digestion process is done once the food particles leave the duodenum.

 

3) Absorbing -  To help increase the rate of absorption, the intestine is covered in villi. The villi increase the surface area of the small intestine. After the small intestine, the food is moved into the large intestine. It takes the unabsorbed material and reabsorbs the minerals and water. By the time the undigested material leaves your large intestine, 90 percent of the water is reabsorbed.

 

4) Eliminating - Any more undigested materials are called feces. Feces are solid waste and are stored in the rectum and eliminated through the anus.

 

Eating Disorders

 

Anorexia Nervosa:

 

People with anorexia nervosa:

  • are very afraid of gaining weight
  • limit the amount of food they eat
  • they feel overweight even though they are dangerously thin
  • have body mass that is less than 85 percent of normal body mass
  • do not menstruate if female 

 

Bulimia Nervosa:

 

People with bulimia nervosa:

 

  • are very concerned about their weight
  • eat a higher than normal amount of food at one sitting and feel they are unable to control this
  • feel overweight even when they are normal
  • body mass is normal or less than normal
  • often have bad breath or gum disease           
                                                                                                                                  *All pictures are collected from the BC Science 8 text book

 

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