The Digestive and E xcretory System

1. The Digestive and Excretory System By Drake http://www.seattlechildrens.org/kids-health/page.aspx?kid=21825&

2. The Mouth http://www.medicalook.com/human_anatomy/organs/Mouth.html You can put any food in your mouth and your body will break down, absorb, and store its nutrients. Food that your body cannot use will be eliminated. This is called digestion, which happens in the digestive system. There are four stages of digestion: ingesting, digesting, absorbing, and then eliminating.

3. Enzymes There are many different chemical reactions happening in your body. Normally, these reactions wont happen at body temperature because they would happen very slowly. An enzyme helps speed up these reactions. In your body, there are many different types of enzymes. There will be one or more enzymes in each organ during the digestion process.

4. Digestion • The digestive system is basically one long tube. The tube is smaller in some places and bigger in others. Digestion breaks down food into small pieces so that the nutrients can be absorbed. The nutrients are then used for maintenance growth and repair. Anything that can’t be used is eliminated.

5. Bibliography • McGraw-Hill Ryerson. BC Science 8.Whitby, ON. McGraw-Hill Ryerson, 2006.

6. Ingesting and Digesting Step 1: Ingesting The starting point of the digestive system is ingesting. Step 2: Digesting The moment you start chewing, you are digesting. Several body structures along the digestive tube are involved in this process.

7. Mechanical and Chemical Digestion http://www.bcscience8.com/pgs/quiz_section2.2.htm Food goes through both chemical and mechanical digestion when it enters your mouth. Mechanical digestion happens when you chew your food into small enough pieces to swallow using your teeth and tongue. Each small piece of food is called a bolus. The bolus is covered in saliva to help it go down the digestive tube before you swallow. An enzyme called amylase is also contained in saliva. Chemical digestion happens when the food bolus is broken down by the amylase. The amylase breaks down complex carbohydrates into simple carbohydrates.

8. The Epiglotis and Pharynx http://www.teachengineering.org/view_lesson.php?url=collection/cub_/lessons/cub_human/cub_human_lesson04.xml After the food moves through your mouth, it goes through the pharynx. The airway passage and the rest of the digestive system meet at the pharynx, which looks like two tubes joining into one. Each tube has a different function, one for digesting and one for breathing, so your body has a way that’s simple and effective of keeping the two tubes separate. The epiglottis, which is a small flap of flesh, covers the airway tube. When you swallow, the food carries on to the esophagus, and the flap covers the airway tube. Peristalsis is the process of the bolus being pushed through the esophagus.

9. Stomach http://tcmdiscovery.com/BasicTheoryofTCM/info/20130528_16860.html Your stomach can hold about 2 liters of food or liquid. There is gastric juice in your stomach, which has an enzyme called pepsin, which breaks down protein. When the food is dropped into the stomach, it gets coated in gastric juice. It can take 2 to 6 hours to fully break down. In your stomach, there are 2 sphincters, which open up to let the food in and out.

10. Small Intestine Once the food is broken down, it becomes a liquid and goes into a small intestine. The small intestine is connected to organs such as the pancreas and the liver. The small intestine is covered in villi, which helps the speed of absorption.

11. Villi • Villi increases the surface area for absorption. With the villi, the small intestine has about the area of a tennis court, or about 250 m2. If the small intestine didn’t have the villi it would only have an area of about 0.5 m2. Usually food takes about 5 to 6 hours to pass through the small intestine.

12. Large Intestine The large intestine reabsorbs all the water and minerals from the small intestine. By the time the food leaves your small intestine, 90% of the water has been reabsorbed. This process takes about 12 to 24 hours.