1. 1 Digestive System Anatomy and Ingestion Chapter 8 Section 8.3

2. 2 Getting Introduced http://kidshealth.org/PageManager.jsp?lic=1&article_set=59299&cat_id=20607 There are 4 main components of the digestive process: 1.Ingestion – the taking in of nutrients. 2.Digestion – the breakdown of complex organic molecules into smaller components by enzymes. 3.Absorption – the transport of digested nutrients to the cells of the body. 4.Egestion – the removal of food waste from the body.

3. 3 The Digestive System Overview AKA Gastrointestinal Tract or GI Tract Consists of both physical and chemical breakdown Entire tract ~ 6.5-9m long. Food is broken down and absorbed into the bloodstream where it is carried by the blood to all body cells. Food that cannot be broken down is excreted. It is essentially a hollow tube.

4. Digestive Anatomy http://www.nelson.com/ABbio20- 30/teacher/protect/otr/Bio2030OTR/attachments/q_LSMs/BIOLSM245.pdf

5. 5 Starts in the MOUTH or ORAL CAVITY Digestion begins in the mouth with the salivary glands and the teeth. The salivary glands contribute to the chemical breakdown and the teeth contribute to the physical breakdown of food. Chemical Break Down:  Salivary glands produce salivary amylase an enzyme that starts to break down carbohydrates into simpler sugars. Physical Break Down:  The teeth chew the food into smaller pieces.  Breaking down food into smaller pieces increases the surface area for chemical break down.

6. 6 Next comes the ESOPHAGUS Once the food has been mashed up into a ball it is referred to as bolus. Bolus enters esophagus, passing the opening of the trachea.  EPIGLOTTIS: flap of tissue that covers the trachea preventing food from “going down the wrong tube.” Food moves to stomach partly by GRAVITY, and partly by PERISTALSIS. oPeristalsis – Rhythmic, wavelike muscular contractions that pushes food to stomach.

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8. 8 Esophageal Sphincter The esophageal sphincter is found at the base of the esophagus. Controls entrance to stomach. RELAXATION allows entrance. CONTRACTION prevents acidic components in stomach from backing up into the esophagus.  Can happen on occasion and cause heart burn

9. 9 Then comes the STOMACH J shaped. Functions: storage, digestion, and pushing food into small intestine. Extreme changes in size Lining of the stomach is like an accordion that allows for extreme expansion and contraction.

10. 10 STOMACH Continued Physical digestion: peristalsis of stomach.  Breaks food into smaller pieces and mixes it with gastric juice.

11. 11 STOMACH Continued Chemical Digestion  Gastric Juice: water + mucus + salts + hydrochloric acid + pepsinogens (enzymes). Very acidic Mixes with mashed up food to make CHYME (thick liquid).

12. 12 STOMACH Continued Why don’t the gastric juices digest the proteins that make up its own cells?  3 methods of protection

13. 13 The Three Methods of Protection 1.Little gastric juice is secreted until food is present. 2.Mucus is secreted from some cells (protects cells lining stomach from low pH). 3.PEPSIN remains inactive until hydrochloric acid (HCl) is present.

14. 14 PEPSIN Pepsin is a protein digesting enzyme. Produced in stomach. Once active (by HCL): hydrolyzes proteins to create smaller polypeptides. - inactive form = Pepsinogen

15. 15 STOMACH Continued Pyloric Sphincter  Controls exit of food from the stomach.  A true sphincter. The esophageal sphincter is not a true sphincter because it does not COMPLETELY SEAL the esophagus from the stomach. We are able to vomit and have heart burn occasionally.

16. PEPTIC ULCERS When the protective lining of the stomach breaks down, the cell membrane is exposed to the HCL and pepsin. Destruction of the cell membrane by these chemicals is known as a peptic ulcer.