1. Warmup 2/16/16 Describe how the digestive system works. Objective Tonight’s Homework To learn how the first half of the digestive system works pp 540: 1-4 Label Coloring sheet

2. Digestive System: Mouth to Stomach Function The digestive system performs 4 functions: 1) Ingestion (or intake) of food material 2) Digestion (or breakdown) of that material. 3) Absorption of that material into the bloodstream. 4) Egestion (or elimination) of waste material out of the body.

3. Digestive System: Mouth to Stomach Mouth Before you’ve even placed food in your mouth, your salivary glands have usually started making saliva. You have 3 glands, and each one secretes saliva. Saliva is a substance that begins breaking down food, especially sugars, right away.

4. Digestive System: Mouth to Stomach The rest of the breakdown of food is done through mastication. This is the process of chewing, using the teeth. As you eat, taste buds (called papilae) in your tongue detect taste. However, it is worth noting that the senses of taste and smell are closely linked, so when you have a cold, your sense of taste is dulled as well as your sense of smell.

5. Digestive System: Mouth to Stomach Taste bud receptors are shown as the larger groups of cells below. As food dissolves, the molecules come into contact with taste buds. These buds have receptors that sense the chemical composition of the food and send an appropriate signal to the brain. These cells sense complex combinations of sweet, sour, salty, bitter, and umami (savory).

6. Digestive System: Mouth to Stomach Teeth Teeth can be broken into 4 categories: 1) Incisors Used for biting 2) Canines Used for tearing

7. Digestive System: Mouth to Stomach 3) Premolars Used for crushing 4) Molars Used for grinding

8. Digestive System: Mouth to Stomach As a child, you grow a set of teeth that you will eventually lose. These are called your deciduous teeth. At this point, you lack premolars and only have room for 20 teeth per set instead of 32.

9. Digestive System: Mouth to Stomach Teeth are made of multiple layers of calcite layered over living tissue in the pulp of the tooth. At the root are nerves and blood vessels to supply nutrients to the tooth.

10. Digestive System: Mouth to Stomach Esophagus and Stomach When you swallow food, it moves into the esophagus. Gravity is not what pulls food down. Instead, food is pushed down through muscular movements called peristaltic contractions. As food enters the stomach, a sphincter at the top closes off. This sphincter – called the cardiac sphincter – helps prevent food and acid from coming back up.

11. Digestive System: Mouth to Stomach Once food reaches the stomach, it is liquefied. This process occurs from the gastric juices in the stomach. Gastric juice is made from 2 things: - A strong acid- Digestive enzymes These things together break down food in a time span from anything as short as 30 minutes to 4 hours. After the food is broken down into chyme, it passes through the pyloric sphincter at the bottom of the stomach.

12. Digestive System: Mouth to Stomach The inner layer is called the mucosa. This layer secretes mucus to protect the stomach lining from its own acid. The next layer is the sub- mucosa. This layer connects to blood vessels to supply nutrients to the stomach cells.

13. Digestive System: Mouth to Stomach Past this is the muscular layer. This layer forms the bulk of the stomach and controls peristaltic contractions. The last layer is the serosa, which connects the stomach to surrounding structures.

14. Digestive System: Mouth to Stomach If the body has ingested something dangerous, a section of the brain called the “fourth ventricle” is stimulated, causing the person to throw up. This section of the brain can be stimulated or suppressed by many factors. Some of these factors can include: bad food, vomiting of other people nearby, chemical triggers to the brain, or extreme stress or shock.

15. Exit Question Define "mastication“ a) The process of chewing b) The process of making saliva c) The process of swallowing d) The process of digesting in the stomach e) The process of putting up a mast f) None of the above