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Two groups of organs Digestive System1. Alimentary canal (gastrointestinal or GI tract) Mouth to anus Digests food and absorbs fragments Mouth, pharynx, esophagus, stomach, small intestine, and large intestine © 2013 Pearson Education, Inc.
2. Accessory digestive organsDigestive System 2. Accessory digestive organs Teeth, tongue, gallbladder Digestive glands Salivary glands Liver Pancreas © 2013 Pearson Education, Inc.
Ingestion Food Mechanical breakdown Pharynx Esophagus Chewing (mouth)Figure Gastrointestinal tract activities. Ingestion Food Mechanical breakdown Pharynx Esophagus Chewing (mouth) Churning (stomach) Propulsion Segmentation (small intestine) • Swallowing (oropharynx) • Peristalsis (esophagus, stomach, small intestine, large intestine) Digestion Stomach Absorption Lymph vessel Small intestine Blood vessel Large intestine Mainly H2O Feces Anus Defecation © 2013 Pearson Education, Inc.
Figure 23.3 Peristalsis and segmentation.From mouth Peristalsis: Adjacent segments of alimentary tract organs alternately contract and relax, moving food along the tract distally. Segmentation: Nonadjacent segments of alimentary tract organs alternately contract and relax, moving food forward then backward. Food mixing and slow food propulsion occur. © 2013 Pearson Education, Inc.
GI Tract Regulatory MechanismsMechano and chemoreceptors Respond to stretch, changes in osmolarity and pH, and presence of substrate and end products of dig Initiate reflexes that Activate or inhibit digestive glands Stimulate smooth muscle © 2013 Pearson Education, Inc.
Central nervous systemFigure Neural reflex pathways initiated by stimuli inside or outside the gastrointestinal tract. External stimuli (sight, smell, taste, thought of food) Central nervous system Long reflexes Visceral afferents Extrinsic visceral (autonomic) efferents Chemoreceptors, osmoreceptors, or mechanoreceptors Local (intrinsic) nerve plexus ("gut brain") Internal (GI tract) stimuli Effectors: Smooth muscle or glands Short reflexes Gastrointestinal wall (site of short reflexes) Response: Change in contractile or secretory activity Lumen of the alimentary canal © 2013 Pearson Education, Inc.
Peritoneum - serous memb of abd cavityVisceral peritoneum on surface of organs Parietal peritoneum lines body wall Peritoneal cavity Between two peritoneums Fluid lubricates mobile organs Peritonitis Abdominal adhesions are bands of fibrous scar tissue that form on organs in the abdomen, causing the organs to stick to one another or to the wall of the abdomen. © 2013 Pearson Education, Inc.
Two schematic cross sections of abdominal cavity illustrate Figure 23.5a The peritoneum and the peritoneal cavity. Abdominopelvic cavity Vertebra Dorsal mesentery Parietal peritoneum Ventral mesentery Visceral peritoneum Peritoneal cavity Alimentary canal organ Liver Two schematic cross sections of abdominal cavity illustrate the peritoneums and mesenteries. © 2013 Pearson Education, Inc.
Peritoneum and Peritoneal CavityMesentery - double layer of peritoneum Routes for BV, lymphatics, and nerves Holds organs in place; stores fat © 2013 Pearson Education, Inc.
Alimentary canal organ in a retroperitoneal positionFigure 23.5b The peritoneum and the peritoneal cavity. Mesentery resorbed and lost Alimentary canal organ Alimentary canal organ in a retroperitoneal position Some organs lose their mesentery and move, becoming retroperitoneal, during development. © 2013 Pearson Education, Inc.
Blood Supply: Splanchnic CirculationBranches of aorta Hepatic, splenic, gastric, mesenteric arteries Hepatic portal circulation © 2013 Pearson Education, Inc.
Myenteric nerve plexusFigure Basic structure of the alimentary canal. Intrinsic nerve plexuses Myenteric nerve plexus Submucosal nerve plexus Glands in submucosa Mucosa Epithelium Lamina propria Muscularis mucosae Submucosa Muscularis externa Longitudinal muscle Circular muscle Serosa Epithelium (mesothelium) Nerve Connective tissue Artery Gland in mucosa Lumen Vein Duct of gland outside alimentary canal Mucosa-associated lymphoid tissue Mesentery Lymphatic vessel © 2013 Pearson Education, Inc.
Enteric Nervous SystemIntrinsic nerve supply – enteric neurons Major nerves to GI tract; control motility Submucosal nerve plexus Regulates glands and smooth muscle in mucosa Myenteric nerve plexus Controls GI tract motility Sympathetic inhibit dig activities Parasympathetic stimulate dig activities © 2013 Pearson Education, Inc.
Sagittal section of the oral cavity and pharynxFigure 23.7a Anatomy of the oral cavity (mouth). Soft palate Palatoglossal arch Uvula Hard palate Oral cavity Palatine tonsil Tongue Oropharynx Lingual tonsil Epiglottis Hyoid bone Laryngopharynx Esophagus Trachea Sagittal section of the oral cavity and pharynx © 2013 Pearson Education, Inc.
Upper lip Gingivae (gums) Superior labial frenulum Palatine rapheFigure 23.7b Anatomy of the oral cavity (mouth). Upper lip Gingivae (gums) Superior labial frenulum Palatine raphe Palatoglossal arch Hard palate Palatopharyngeal arch Soft palate Uvula Palatine tonsil Posterior wall of oropharynx Tongue Sublingual fold with openings of sublingual ducts Lingual frenulum Opening of Submandibular duct Gingivae (gums) Oral vestibule Inferior labial frenulum Lower lip Anterior view © 2013 Pearson Education, Inc.
Epiglottis Palatopharyngeal arch Palatine tonsil Lingual tonsilFigure Dorsal surface of the tongue, and the tonsils. Epiglottis Palatopharyngeal arch Palatine tonsil Lingual tonsil Palatoglossal arch Terminal sulcus Foliate papillae Vallate papilla Medial sulcus of the tongue Dorsum of tongue Fungiform papilla Filiform papilla © 2013 Pearson Education, Inc.
Figure 23.9 The salivary glands.Tongue Teeth Parotid gland Ducts of sublingual gland Parotid duct Masseter muscle Frenulum of tongue Body of mandible (cut) Sublingual gland Posterior belly of digastric muscle Mylohyoid muscle (cut) Submandibular duct Anterior belly of digastric muscle Submandibular gland Mucous cells Serous cells forming demilunes © 2013 Pearson Education, Inc.
Two types of secretory cellsSalivary Glands Two types of secretory cells Serous cells Watery, enzymes, ions, bit of mucin Mucous cells Mucus Parotid, submandibular glands mostly serous; sublingual mostly mucous © 2013 Pearson Education, Inc.
97–99.5% water, slightly acidicComposition of Saliva 97–99.5% water, slightly acidic Electrolytes—Na+, K+, Cl–, PO4 2–, HCO3– Salivary amylase and lingual lipase Mucin Metabolic wastes—urea and uric acid Lysozyme, IgA, defensins, and a cyanide compound protect against microorganismsa PLAY Animation: Rotating head © 2013 Pearson Education, Inc.
Control of Salivation 1500 ml/day activated by parasympathetic whenIngested food stimulates chemoreceptors and mechanoreceptors in mouth Salivatory nuclei in brain stem send impulses along parasympathetic fibers in cranial nerves VII and IX Sympathetic inhibits salivation results xerostomia © 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
Primary and permanent dentitions formed by age 21 Teeth Primary and permanent dentitions formed by age 21 20 deciduous teeth erupt (6–24 months of age) Roots resorbed, teeth fall out (6–12 years of age) as permanent teeth develop 32 permanent teeth All but third molars in by end of adolescence Third molars at 17–25, or may not erupt © 2013 Pearson Education, Inc.
© 2013 Pearson Education, Inc.
Figure 23.10 Human dentition.Incisors Central (6–8 mo) Lateral (8–10 mo) Canine (eyetooth) (16–20 mo) Molars First molar (10–15 mo) Deciduous (milk) teeth Second molar (about 2 yr) Incisors Central (7 yr) Lateral (8 yr) Canine (eyetooth) (11 yr) Premolars (bicuspids) First premolar (11 yr) Second premolar (12–13 yr) Molars First molar (6–7 yr) Second molar (12–13 yr) Third molar (wisdom tooth) (17–25 yr) Permanent teeth © 2013 Pearson Education, Inc.
Shorthand indicator of number/position of teethDental Formulas Shorthand indicator of number/position of teeth Ratio of upper to lower teeth for 1/2 of mouth Primary: Permanent: © 2013 Pearson Education, Inc.
Crown - exposed part above gingiva (gum)Tooth Structure Crown - exposed part above gingiva (gum) Covered by enamel—hardest substance in body (calcium salts and hydroxyapatite crystals) Enamel-producing cells degenerate when tooth erupts no healing if decay or crack Root - portion embedded in jawbone Connected to crown by neck © 2013 Pearson Education, Inc.
Cement - calcified connective tissue Periodontal ligamentTooth Structure Cement - calcified connective tissue Covers root; attaches to periodontal ligament Periodontal ligament Fibrous joint called gomphosis Anchors tooth in socket Gingival sulcus - groove where gingiva borders tooth © 2013 Pearson Education, Inc.
Dentin - bonelike material under enamel Tooth Structure Dentin - bonelike material under enamel Maintained by odontoblasts of pulp cavity Pulp cavity - surrounded by dentin Pulp - connective tissue, BV, and nerves Root canal - as pulp cavity extends to root Apical foramen at proximal end of root Entry for blood vessels, nerves, etc. © 2013 Pearson Education, Inc.
Enamel Dentin Cement Root canal BoneFigure Longitudinal section of a canine tooth within its bony socket (alveolus). Enamel Dentin Crown Dentinal tubules Pulp cavity (contains blood vessels and nerves) Neck Gingival sulcus Gingiva (gum) Cement Root canal Root Periodontal ligament Apical foramen Bone © 2013 Pearson Education, Inc.
Tooth and Gum Disease Dental caries (cavities) - demineralization of enamel and dentin from bacterial action Dental plaque (film of sugar, bacteria, and debris) adheres to teeth Acid from bacteria dissolves calcium salts Proteolytic enzymes digest organic matter Prevention: daily flossing and brushing © 2013 Pearson Education, Inc.
Tooth and Gum Disease GingivitisPlaque calcifies to form calculus (tartar) Calculus disrupts seal between gingivae and teeth Bacteria infect gums © 2013 Pearson Education, Inc.
Periodontitis -Immune cells attackTooth and Gum Disease Periodontitis -Immune cells attack Destroy periodontal ligament Activate osteoclasts dissolve bone Tooth loss; may promote atherosclerosis Risk factors ? © 2013 Pearson Education, Inc.
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