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This 9 page Class Notes was uploaded by Jess Graff on Monday May 2, 2016. The Class Notes belongs to BMS 508 at University of New Hampshire taught by Mary Katherine Lockwood, PhD in Spring 2016. Since its upload, it has received 3 views. For similar materials see Human Anatomy and Physiology II in Biological Sciences at University of New Hampshire.
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Date Created: 05/02/16
BMS 508.03 4/4/2016 Chapter 24 (cont) Digestion & Metabolism (cont) The Oral Cavity • Parotid Salivary Glands • Inferior to zygomatic arch • Produce serous secretion • Enzyme salivary amylase (breaks down starches) • Drained by parotid duct • Which empties into vestibule at second molar • Sublingual Salivary Glands • Covered by mucous membrane of floor of mouth • Produce mucous secretion • Acts as a buffer and lubricant • Sublingual ducts • Either side of lingual frenulum • Submandibular Salivary Glands • In floor of mouth • Within mandibular groove • Secrete buffers, glycoproteins (mucins), and salivary amylase • Submandibular ducts • Open immediately posterior to teeth • Either side of lingual frenulum • Saliva • Glands produce 1.0–1.5 liters of saliva each day • 70% by submandibular glands • 25% by parotids • 5% by sublingual glands • 99.4% water • 0.6% includes: • Electrolytes (Na , Cl , and HCO ) 3− • Buffers • Glycoproteins (mucins) • Antibodies • Enzymes • Waste products • Functions of Saliva • Lubricating the mouth • Moistening and lubricating materials in the mouth • Dissolving chemicals that stimulate taste buds and provide sensory information • Initiating digestion of complex carbohydrates by the enzyme salivary amylase (ptyalin or alpha-amylase) • Control of Salivary Secretions • By autonomic nervous system • Parasympathetic and sympathetic innervation • Parasympathetic accelerates secretion by all salivary glands • Salivatory nuclei of medulla oblongata influenced by: • Other brain stem nuclei • Activities of higher centers • The Teeth • Tongue movements pass food across occlusal surfaces of teeth • Chew (masticate) food • Dentin • A mineralized matrix similar to that of bone • Does not contain cells • Pulp Cavity • Receives blood vessels and nerves through the root canal • Root • Of each tooth sits in a bony socket (alveolus) • A layer of cementum covers dentin of the root • Providing protection and anchoring periodontal ligament • Crown • Exposed portion of tooth • Projects beyond soft tissue of gingiva • Dentin covered by layer of enamel • Alveolar Processes • Of the maxillae • Form maxillary arcade (upper dental arch) • Of the mandible • Form mandibular arcade (lower dental arch) • Types of Teeth • Incisors • Cuspids (canines) • Bicuspids (premolars) • Molars • Incisors • Blade-shaped teeth • Located at front of mouth • Used for clipping or cutting • Have a single root • Cuspids (Canines) • Conical • Sharp ridgeline • Pointed tip • Used for tearing or slashing • Have a single root • Bicuspids (Premolars) • Flattened crowns • Prominent ridges • Used to crush, mash, and grind • Have one or two roots • Molars • Very large, flat crowns • With prominent ridges • Used for crushing and grinding • Have three or more roots • Dental Succession • During embryonic development, two sets of teeth form • Primary dentition, or deciduous teeth • Secondary dentition, or permanent dentition • Deciduous Teeth • Also called primary teeth, milk teeth, or baby teeth • 20 temporary teeth of primary dentition • Five on each side of upper and lower jaws • 2 incisors • 1 cuspid • 2 deciduous molars • Secondary Dentition • Also called permanent dentition • Replaces deciduous teeth • 32 permanent teeth • Eight on each side, upper and lower • 2 incisors • 1 cuspid • 5 molars • Mastication • Also called chewing • Food is forced from oral cavity to vestibule and back • Crossing and recrossing occlusal surfaces • Muscles of Mastication • Close the jaws • Slide or rock lower jaw from side to side • Chewing involves mandibular: • Elevation and depression • Protraction and retraction • Medial and lateral movement The Pharynx • The Pharynx (Throat) • A common passageway for solid food, liquids, and air • Regions of the pharynx: • Nasopharynx • Oropharynx • Laryngopharynx • Food passes through the oropharynx and laryngopharynx to the esophagus The Esophagus • The Esophagus • A hollow muscular tube • About 25 cm (10 in.) long and 2 cm (0.80 in.) wide • Conveys solid food and liquids to the stomach • Begins posterior to cricoid cartilage • Enters abdominopelvic cavity through the esophageal hiatus • Is innervated by fibers from the esophageal plexus • Resting Muscle Tone • In the circular muscle layer in the superior 3 cm (1.2 in.) of esophagus prevents air from entering • Histology of the Esophagus • Wall of esophagus has three layers • Mucosal • Submucosal • Muscularis • Histology of the Esophagus • Mucosa contains: • Nonkeratinized and stratified squamous epithelium • Mucosa and submucosa form: • Large folds that extend the length of the esophagus • Muscularis mucosae consists of: • Irregular layer of smooth muscle • Submucosa contains esophageal glands • Which produce mucous secretion • Reduces friction between bolus and esophageal lining • Muscularis externa has: • Usual inner circular and outer longitudinal layers • Swallowing • Also called deglutition • Can be initiated voluntarily • Proceeds automatically • Is divided into 3 phases • Buccal phase • Pharyngeal phase • Esophageal phase The Stomach • Major Functions of the Stomach 1. Storage of ingested food 2. Mechanical breakdown of ingested food 3. Disruption of chemical bonds in food material by acid and enzymes 4. Production of intrinsic factor, a glycoprotein required for absorption of vitamin B 12in small intestine • Anatomy of the Stomach 1. The stomach is shaped like an expanded J • Short lesser curvature forms medial surface • Long greater curvature forms lateral surface 2. Anterior and posterior surfaces are smoothly rounded 3. Shape and size vary from individual to individual and from one meal to the next 4. Stomach typically extends between levels of vertebrae T and L 7 3 • Regions of the Stomach 1. Cardia 2. Fundus 3. Body 4. Pylorus • Smooth Muscle • Muscularis mucosae and muscularis externa • Contain extra layers of smooth muscle cells • Oblique layer in addition to circular and longitudinal layers • Histology of the Stomach • Simple columnar epithelium lines all portions of stomach • Epithelium is a secretory sheet • Produces mucus that covers interior surface of stomach • Gastric pits, shallow depressions that open onto the gastric surface • Mucous cells, at the base, or neck, of each gastric pit, actively divide, replacing superficial cells • Gastric Glands • In fundus and body of stomach • Extend deep into underlying lamina propria • Each gastric pit communicates with several gastric glands • Parietal cells • Chief cells • Parietal Cells • Secrete intrinsic factor and hydrochloric acid (HCl) • Chief Cells • Are most abundant near base of gastric gland • Secrete pepsinogen (inactive proenzyme) • Pepsinogen • Is converted by HCl in the gastric lumen • To pepsin (active proteolytic enzyme) • Pyloric Glands • Located in the pylorus • Produce mucous secretion • Scattered with enteroendocrine cells • G cells produce gastrin • D cells release somatostatin, a hormone that inhibits release of gastrin • Regulation of Gastric Activity • Production of acid and enzymes by the gastric mucosa can be: • Controlled by the CNS • Regulated by short reflexes of ENS • Regulated by hormones of digestive tract • 3 phases of gastric control • Cephalic phase • Gastric phase • Intestinal phase
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