Lec10 Digestive System

Lec10 Digestive - Chapter 8 Digestive System and Nutrition What are the main steps in the digestive process Ingestion intake of food via the mouth

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Chapter 8 Digestive System and Nutrition
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What are the main steps in the digestive process? Ingestion – intake of food via the mouth Digestion – mechanically or chemically breaking down food into their subunits Movement – food must be moved along the GI tract in order to fulfill all functions Absorption – movement of nutrients across the GI tract wall to be delivered to cell via the blood Elimination – removal of indigestible molecules
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What are the 4 major layers that make up the wall of the GI tract? Mucosa – innermost layer that produces mucus that protect the lining and also produce digestive enzymes Submucosa – 2nd layer of loose connective tissue that contains blood vessels, lymphatic vessels and nerves Muscularis – 3rd layer made of 2 layers of smooth muscle that move food along the GI tract Serosa – outer lining that is part of the peritoneum
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Visualizing the layers of the GI tract
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An overview of the digestive system Digestive tract is a term for the complete path of food from the mouth to the anus
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What is the pathway that food follows? mouth pharynx esophagus stomach small intestine large intestine rectum anus
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The first part of the digestive tract includes the: Mouth Pharynx Esophagus
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The mouth 3 pairs of salivary glands secrete salivary amylase that begins carbohydrate digestion Tonsils at the back of the mouth and other lymphatic tissues are important in fighting disease Contains teeth that begin the mechanical breakdown of food The tongue is covered in taste buds and also assists in the mechanical breakdown and movement of food The tongue forms a bolus (mass of chewed food) and moves it toward the pharynx
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Anatomy of the mouth
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Teeth 32 in adults used for mechanical breakdown of food (20 deciduous teeth in babies) Each tooth is made of a crown and a root A hard covering called enamel and dentin covers the crown with an inner pulp area with nerves and blood vessels Dental caries (cavities) occur when bacteria metabolize sugars and produce acids so limiting sugar intake and brushing teeth reduces these
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Anatomy of a tooth
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The pharynx and esophagus Pharynx is a cavity between the mouth and esophagus that serves as a passageway for food (and air) Esophagus is a long, muscular tube that carries food to the stomach
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How do we swallow food? Voluntary phase : The beginning of food being swallowed from the mouth into the pharynx Involuntary phase : Once the food is in the pharynx swallowing becomes a reflex The epiglottis covers the voice box to make sure food is routed into the esophagus Food moves down the esophagus through peristalsis (rhythmic contraction)
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How do we swallow food?
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Health focus: Heartburn Occurs when acids from the stomach pass into the esophagus (acid reflux) Burning sensation in the esophagus Chronic heartburn is called gastroesophageal reflux disease (GERD) Tips for decreasing heartburn:
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This note was uploaded on 04/07/2009 for the course BIOL 115 taught by Professor Irving during the Spring '08 term at Illinois Tech.

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Lec10 Digestive - Chapter 8 Digestive System and Nutrition What are the main steps in the digestive process Ingestion intake of food via the mouth

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