Unit 7-Lecture 1.ppt - Unit 7-Digestive System Lecture...

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Unit 7-Digestive System Lecture 1-Components of the Digestive System
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Introduction Food contains substances and energy the body needs to construct all cell components. The food must be broken down through digestion to molecular size before it can be absorbed by the digestive system and used by the cells. The organs that collectively perform these functions compose the digestive system.
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Components Include the Gastrointestinal (GI) tract Accessory structures/glands including: teeth, tongue, salivary glands, liver, gall bladder and pancreas
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Layers of the GI tract The basic arrangement of layers in the gastrointestinal tract from the deep to superficial includes the mucosa , submucosa , muscularis , and serosa (visceral peritoneum).
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Layers of the GI Tract 1. Mucosal layer 2. Submucosal layer 3. Muscularis layer 4. Serosa layer
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Mucosa Epithelium stratified squamous(in mouth,esophagus & anus) = tough simple columnar in the rest secretes enzymes and absorbs nutrients specialized cells (goblet) secrete mucous onto cell surfaces Lamina propria Layer of loose CT Muscularis mucosae thin layer of smooth muscle
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Submucosa Loose connective tissue containing BV, glands and lymphatic tissue and nerve plexus
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Muscularis Skeletal muscle = voluntary control in mouth, pharynx , upper esophagus and anus control over swallowing and defecation Smooth muscle = involuntary control inner circular fibers & outer longitudinal fibers mixes, crushes & propels food along by peristalsis
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Serosa An example of a serous membrane Covers all organs and walls of cavities not open to the outside of the body Secretes slippery fluid Consists of connective tissue covered with simple squamous epithelium
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The GI Tract Oral Cavity -> pharynx -> esophagus -> lower esophageal sphincter -> stomach (cardia, fundus, body, pyrolus) -> Pyloric sphincter -> small intestine (duodenum, jejunum, ileum) -> large intestine (cecum with appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum) -> anal sphincter -> anus
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Oral Cavity (Mouth) Functions: Temporary storage of food while chewing Tasting of food Start digestion of starch by salivary amylase Chewing (mastication) of food
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Teeth Used for the mechanical breakdown of food and to articulate speech
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