Heterotrophic Nutrition & The Human Digestive System

Heterotrophic Nutrition Heterotrophs are organisms who are unable to produce their own food and therefore must obtain food from an external source. Examples: Bacteria Protozoans (amebas) Fungi Animals

Processes involved in Heterotrophic Nutrition 1. Ingestion – taking in food by mouth (eating) 2. Digestion – breaking down large molecules into small ones There are two types of digestion: Mechanical digestion – food is broken down by cutting, grinding, and tearing. Increase the food’s surface area for chemical digestion Chemical digestion – large molecules are broken down into smaller ones by enzymatic hydrolysis. Hydrolysis – splitting molecules by adding water Digestion = Hydrolysis 3. Egestion – removal of undigested or undigestible material.

Products of Chemical Digestion Before Hydrolysis After Hydrolysis Complex Carbohydrates Sugars Proteins Amino Acids Lipids Fatty acids & glycerol

Human Nutrition Nutrients – substances an organism needs to live. There are 6 basic nutrients in food. Some must be digested before being absorbed: Carbohydrates Proteins Lipids Some do not have to be digested before being absorbed: Vitamins Minerals Water

Human Nutritional Requirements Nutrient requirements vary with age

What are some important Nutrients? Roughage (Fiber, a carbohydrate) - indigestible materials in food (Fruits, vegetables, grains). Roughage stimulates proper functioning of muscles in the digestive tract. Proteins are made from 20 different amino acids. We can synthesize 12 of those amino acids. The other 8 must be from our diet and are called the 8 essential amino acids. Water is needed for chemical reactions to occur in the body.

Roles of Nutrients Without vitamins and minerals, your body will not function properly.

Roles of Nutrients Not all forms of nutrients are good for you: Saturated Fats - are solid at room temperature and are linked to cardiovascular disease. Polyunsaturated Fats - are liquid at room temperature and are not linked to cardiovascular disease.

Human Digestive System The human digestive system breaks down food into smaller molecules that can be absorbed into the blood and transported to cells throughout the body. It is a one way tube that travels from the mouth to the anus. Also called: The Alimentary Canal The Gastrointestinal Tract

Human Digestive System Mouth Salivary Glands Liver Gallbladder Esophagus Stomach Pancreas Small Intestine Large Intestine Anus Rectum Epiglottis Salivary Glands Salivary Glands Mouth Mouth Esophagus Esophagus Epiglottis Epiglottis Liver Liver Stomach Stomach Gallbladder Gallbladder Pancreas Pancreas Small Intestine Small Intestine Large Intestine Large Intestine Rectum Rectum Anus Anus

Human Digestive System The Oral Cavity (Mouth) Structures & Functions Teeth – perform mechanical digestion by tearing, crushing and grinding food into smaller pieces. Salivary Glands – perform chemical digestion of carbohydrates through amylase (enzyme that digests starch). Tongue – pushes food to the back of the mouth so it can be swallowed.

Human Digestive System The Epiglottis It is a flap at the back of the throat that covers the esophagus & trachea (windpipe). It covers the trachea during swallowing to keep food from entering the respiratory system (prevents choking).

Human Digestive System The Esophagus A tube that connects the mouth to the stomach. No digestion occurs here. Food moves through by peristalsis (involuntary muscle contractions).

Human Digestive System The Stomach A muscular organ Performs mechanical digestion (churns and mixes food) Releases gastric juice (a mixture of HCl, hydrochloric acid, and proteases) to begin the chemical digestion of proteins.

Human Digestive System The Small Intestine A long, tubular organ (20–25 feet long) Digestive enzymes are released into the small intestine from the gall bladder and pancreas. All chemical digestion is finished here. End products of digestion are absorbed through villi. Peristalsis moves materials through the small intestine.

Human Digestive System The Small Intestine - Villi Villi are small finger-like projections in the small intestine. They increase surface area in the small intestine. Villi absorb products of digestion into the blood stream.

Human Digestive System The Large Intestine A tubular organ (5 feet long) No digestion occurs here. Water is absorbed. Undigested materials pass through and are left behind to be egested as feces. Peristalsis moves materials through the large intestine.

Human Digestive System The Rectum and Anus The rectum stores feces before egestion. Feces are egested through the anus. No digestion or absorption occurs here. Peristalsis moves materials through the rectum and anus.

Additional Structures of the Human Digestive System 1. Liver – produces bile, which emulsifies fats. 2. Gallbladder – stores bile and releases it into the small intestine. 3. Pancreas – produces proteases and releases them into the small intestine.

Human Digestive System Emulsification Emulsification is an example of mechanical digestion. Bile emulsifies fats by breaking fat globules down into small droplets that can easily be chemically digested in the small intestine. Fat Globule Bile Fat Droplets

Disorders of the Human Digestive System 1. Ulcers - an erosion of the surface of the alimentary canal. Caused by bacteria, NOT stress! 2. Constipation - too much water is absorbed by the large intestine and egestion is difficult. 3. Diarrhea – too little water is absorbed by the large intestine, combined with increased peristaltic activity of the large intestine.

Disorders of the Human Digestive System 4. Appendicitis - inflammation of the appendix. 5. Gall Stones - hardened cholesterol deposits in the gall bladder. Blocks the release of bile into the small intestine.

Name that Body Part – Digestive System Edition! Salivary Glands Mouth (oral cavity) Epiglottis Tongue Esophagus Stomach Liver Pancreas Large Intestine Small Intestine Rectum Appendix Anus