Chapter 24, part 2 The Digestive System

SECTION 24-2 The Oral Cavity

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

Oral cavity Lined by oral mucosa Roof of cavity = hard and soft palates Floor of cavity = tongue Uvula guards opening to pharynx

Figure 24.6 The Oral Cavity Figure 24.6a, b

The tongue primary functions include: Mechanical processing Assistance in chewing and swallowing Sensory analysis by touch, temperature, and taste receptors

Tongue movements involve Extrinsic and intrinsic tongue muscles Innervated by the hypoglossal nerve

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

Figure 24.7 The Salivary Glands Figure 24.7a, b

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

Eruption of teeth 20 primary teeth AKA deciduous teeth 32 teeth of secondary dentition

Figure 24.8 Teeth Figure 24.8a, b

Figure 24.9 Primary and Secondary Teeth Figure 24.9a, b

SECTION 24-3 The Pharynx

The pharynx Common passageway for food, liquids, and air Lined with stratified squamous epithelium Pharyngeal muscles assist in swallowing Pharyngeal constrictor muscles Palatal muscles

SECTION 24-4 The Esophagus

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

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

Figure 24.10 The Esophagus Figure 24.10a-c

Swallowing (deglutition) Buccal phase Pharyngeal phase Esophageal phase

Figure 24.11 The Swallowing Process Figure 24.11a-h

SECTION 24-5 The Stomach

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

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

Stomach anatomy Phloric Sphincter Guards exit from stomach Rugae Ridges and folds in relaxed stomach

Figure 24.12 The Stomach Figure 24.12b