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Chapter 24, part 2 The Digestive System
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SECTION 24-2 The Oral Cavity
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The mouth opens into the oral or buccal cavity
Its functions include: Analysis of material before swallowing Mechanical processing by the teeth, tongue, and palatal surfaces Lubrication Limited digestion
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Oral cavity Lined by oral mucosa
Roof of cavity = hard and soft palates Floor of cavity = tongue Uvula guards opening to pharynx
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Figure The Oral Cavity Figure 24.6a, b
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The tongue primary functions include: Mechanical processing
Assistance in chewing and swallowing Sensory analysis by touch, temperature, and taste receptors
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Tongue movements involve
Extrinsic and intrinsic tongue muscles Innervated by the hypoglossal nerve
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Salivary glands (three pairs)
Parotid, sublingual, and submandibular Saliva watery solution electrolytes, buffers, glycoproteins, antibodies, enzymes Functions include: Lubrication, moistening, and dissolving Initiation of digestion of complex carbohydrates PLAY Animation: Mastication Flythrough
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Figure 24.7 The Salivary Glands
Figure 24.7a, b
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Teeth Function in mastication of bolus Contact of occlusal surfaces
Contain three layers Enamel covering crown Dentin forms basic structure Root coated with cementum Periodontal ligaments hold teeth in alveoli
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Eruption of teeth 20 primary teeth AKA deciduous teeth
32 teeth of secondary dentition
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Figure Teeth Figure 24.8a, b
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Figure 24.9 Primary and Secondary Teeth
Figure 24.9a, b
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SECTION The Pharynx
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The pharynx Common passageway for food, liquids, and air
Lined with stratified squamous epithelium Pharyngeal muscles assist in swallowing Pharyngeal constrictor muscles Palatal muscles
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SECTION 24-4 The Esophagus
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The esophagus Carries solids and liquids from the pharynx to the stomach Passes through esophageal hiatus in diaphragm The wall of the esophagus contains mucosal, submucosal, and muscularis layers
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Histology of the esophagus
Distinctive features of the esophageal wall include Nonkeratinized, stratified squamous epithelium Folded mucosa and submucosa Mucous secretions by esophageal glands A muscularis with both smooth and skeletal muscle portions Lacks serosa Anchored by an adventitia
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Figure The Esophagus Figure 24.10a-c
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Swallowing (deglutition)
Buccal phase Pharyngeal phase Esophageal phase
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Figure 24.11 The Swallowing Process
Figure 24.11a-h
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SECTION The Stomach
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Functions of the stomach
Bulk storage of undigested food Mechanical breakdown of food Disruption of chemical bonds via acids and enzymes Production of intrinsic factor
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Anatomy of the stomach Cardia – superior, medial portion
Fundus – portion superior to stomach-esophageal junction Body – area between the fundus and the curve of the J Pylorus – antrum and pyloric canal adjacent to the duodenum
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Stomach anatomy Phloric Sphincter Guards exit from stomach Rugae
Ridges and folds in relaxed stomach
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Figure The Stomach Figure 24.12b
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