1. Digestive Structures Unit D – Human Systems

2. Breaking down digestion There are four components to the process of digestion: 1. Ingestion  taking food into your body. 2. Digestion  breakdown of food by enzymes. 3. Absorption  transportation of digested food to the cells of the body.

3. Review Video Digestion Review Video

4. 4. Egestion  Removal of food waste from body.

5. Physical Digestion Also known as mechanical digestion. Breaks up large pieces of food into smaller pieces. Purpose is to increase surface area so that enzymes can break down small pieces of food. Examples: chewing by teeth, churning of stomach.

6. Chemical Digestion Use of enzymes (NOT CHEMICALS) to break down food into small enough pieces that it can be absorbed into your bloodstream. NOTE: In this section, enzymes will be denoted by italics.

7. Salivary glands Release watery fluid called saliva into your mouth. Saliva dissolves food particles, lubricates food so it can be swallowed, and allows you to taste food. Saliva contains amylase enzyme. Saliva Secretion Video Clip

8. Mouth/Teeth Food enters here and is broken down into smaller pieces by teeth. Different teeth are specialized for cutting, tearing, grinding and crushing your food. Tongue forms saliva and food into a ball or bolus, which is ready to move down your throat.

9. Esophagus Tube that connects your mouth to your stomach. Bolus of food stretches the walls of the esophagus, activating waves of contractions called peristalsis which move food along your gastrointestinal tract. Entry into the stomach is control by a muscle called a sphincter.

10. Stomach Site of food storage and beginning of protein digestion. Can hold about 1.5 L of food. Stomach fluids are also called gastric fluids.

11. The three major components of gastric fluids are hydrochloric acid, mucus and pepsinogen. Hydrochloric acid destroys bacteria that enter the body along with food. Hydrochloric acid activates pepsinogen enzyme into its active form called pepsin.

12. In order to protect your stomach from the hydrochloric acid, it is lined with an alkaline or basic layer of mucus. Food material will now be in liquid form and passes through the pyloric sphincter to enter the small intestine.

13. Small Intestines Major site of chemical digestion and absorption of food into the bloodstream. Approximately 7 metres in length. Has a basic pH of around 9. Covered with long fingerlike projections called villi, which increase the surface area of the small intestine.

15. Increased surface area for absorption means that more nutrients can be absorbed. Each villus (singular of villi) has its own blood supply and lymphatic supply, so that absorbed food can be taken to cells all around the body.

16. Digested carbohydates (monosaccharides) and proteins (amino acids) are absorbed into the bloodstream. Digested fats are too large to move into the bloodstream and enter lacteals, which are transportation tubes that make up the lymphatic system.

17. Large Intestine Major site of water reabsorption and stores undigested food. Bacteria like E.coli live here and breakdown waste material to make vitamins B and K. Undigested plant material (cellulose, fiber) builds up in your large intestine.

18. When enough waste is present, the intestinal walls are stretched, a signal is sent to the central nervous system and waste is eliminated from the body. Bowel movements make sure that toxic substances can be removed from the body.

19. Student Tasks Draw a flow chart linking the major organs of digestion and summarizing the basic functions of each. Label digestive system diagram. Complete pg. 263 #2,3,5,6,7,13,14,15 for your homework book. Review your notes and key terms for tomorrow’s class.