Why do we need food? Gives us energy to function. Provides body with materials to grow and repair tissue. Nutrients – Carbohydrates (CHO), fats, proteins, vitamins, minerals, and water.

The Functions of the Digestive System 1. Breaks down food into smaller bits and then into molecules. 2. Food molecules, glucose and proteins, are absorbed into the blood. 3.Blood carries nutrients throughout the body. 4. Undigested food, wastes, are eliminated from the body

Digestion Digestion – Process of the body breaking down food into small nutrient molecules.

Types of Digestion 1. Mechanical Digestion – the tearing, grinding and mashing of food. Occurs in mouth and stomach 2. Chemical Digestion – chemicals are added to food to help in the final break down so it can be absorbed. Enzyme – proteins that speed up chemical reactions.

Absorption Absorption – the process where nutrient molecules pass through the walls of your digestive tract into your blood stream.

Digestion Begins 1.THE MOUTH – mechanical and chemical digestion - Teeth tear and grind food – mechanical - Saliva mixes with food and contains an enzyme that starts chemical digestion. 2. THE ESOPHAGUS Esophagus – the muscular tube that leads from the mouth to the stomach. Lined with mucus. - Food only remains in the esophagus for about 10 seconds so very little digestion takes place here.

The epiglottis is a flap of tissue that covers the trachea when we eat. Peristalsis – waves of muscle contractions in the walls of the digestive tract that push food through. Food does NOT slide down any part of the digestive tract.

Digestion Begins (cont.) 3. THE STOMACH (Hyperlink to Stomach noises) - Both Mechanical and Chemical digestion take place in the stomach. - Food is mashed and ground down into a liquid (chyme) and mixed with hydrochloric acid (HCl) and pepsin (an enzyme). - Nutrients are NOT absorbed into the body from the stomach.

- Gastric juices in our stomach help digest food. 1. Pepsin – helps digest protein 2. Hydrochloric Acid (HCL) – Kills bacteria in our stomach Stomach is lined with MUCUS to protect it from the acid.

Final Digestion 4. THE SMALL INTESTINE - Longest part of digestive system - Where MOST of chemical digestion takes place. - Where MOST of the nutrients are absorbed into the bloodstream.

Absorption in the Small Intestine Villi – millions of finger-like projections that cover the inside of the small intestine. Villi increase the surface area of the intestines so we can absorb more nutrients

Final Digestion (cont.) 5. THE LIVER - Produces Bile – a chemical that breaks up fat. Stored in Gall Bladder - Filters blood - Where blood gets iron 6. THE PANCREAS - Produces enzymes that break food down into very small molecules

Final Digestion (cont.) 7. THE LARGE INTESTINE - Contains bacteria that feed on undigested food. - Reabsorbs water from waste before the waste is eliminated. 8. THE RECTUM - Compresses waste into solid form. 9. THE ANUS – opening at the end of the rectum.