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© 2013 Pearson Education, Inc. Digestive System Two groups of organs 1. Alimentary canal (gastrointestinal or GI tract) Mouth to anus Digests food and.

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Presentation on theme: "© 2013 Pearson Education, Inc. Digestive System Two groups of organs 1. Alimentary canal (gastrointestinal or GI tract) Mouth to anus Digests food and."— Presentation transcript:

1 © 2013 Pearson Education, Inc. Digestive System Two groups of organs 1. Alimentary canal (gastrointestinal or GI tract) Mouth to anus Digests food and absorbs fragments Mouth, pharynx, esophagus, stomach, small intestine, and large intestine

2 © 2013 Pearson Education, Inc. Digestive System 2. Accessory digestive organs Teeth, tongue, gallbladder Digestive glands –Salivary glands –Liver –Pancreas

3 © 2013 Pearson Education, Inc. Figure 23.2 Gastrointestinal tract activities. Ingestion Mechanical breakdown Digestion Propulsion Absorption Defecation Food Pharynx Esophagus Chewing (mouth) Swallowing (oropharynx) Peristalsis (esophagus, stomach, small intestine, large intestine) Stomach Lymph vessel Small intestine Large intestine Blood vessel Mainly H 2 O Feces Anus Churning (stomach) Segmentation (small intestine)

4 © 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.

5 © 2013 Pearson Education, Inc. GI Tract Regulatory Mechanisms 1.Mechano 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

6 © 2013 Pearson Education, Inc. Figure 23.4 Neural reflex pathways initiated by stimuli inside or outside the gastrointestinal tract. External stimuli (sight, smell, taste, thought of food) Visceral afferents Internal (GI tract) stimuli Chemoreceptors, osmoreceptors, or mechanoreceptors Long reflexes Central nervous system Local (intrinsic) nerve plexus ("gut brain") Effectors: Smooth muscle or glands Extrinsic visceral (autonomic) efferents Short reflexes Lumen of the alimentary canal Gastrointestinal wall (site of short reflexes) Response: Change in contractile or secretory activity

7 © 2013 Pearson Education, Inc. Peritoneum - serous memb of abd cavity –Visceral 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.

8 © 2013 Pearson Education, Inc. Figure 23.5a The peritoneum and the peritoneal cavity. Abdominopelvic cavity Vertebra Peritoneal cavity Alimentary canal organ Liver Two schematic cross sections of abdominal cavity illustrate the peritoneums and mesenteries. Ventral mesentery Parietal peritoneum Visceral peritoneum Dorsal mesentery

9 © 2013 Pearson Education, Inc. Peritoneum and Peritoneal Cavity Mesentery - double layer of peritoneum –Routes for BV, lymphatics, and nerves –Holds organs in place; stores fat

10 © 2013 Pearson Education, Inc. Figure 23.5b The peritoneum and the peritoneal cavity. Alimentary canal organ Alimentary canal organ in a retroperitoneal position Some organs lose their mesentery and move, becoming retroperitoneal, during development. Mesentery resorbed and lost

11 © 2013 Pearson Education, Inc. Blood Supply: Splanchnic Circulation Branches of aorta –Hepatic, splenic, gastric, mesenteric arteries Hepatic portal circulation

12 © 2013 Pearson Education, Inc. Figure 23.6 Basic structure of the alimentary canal. Intrinsic nerve plexuses Mucosa Submucosa Muscularis externa Glands in submucosa Serosa Lumen Mucosa-associated lymphoid tissue Duct of gland outside alimentary canal Gland in mucosa Lymphatic vessel Vein Artery Nerve Mesentery Myenteric nerve plexus Submucosal nerve plexus Epithelium Lamina propria Muscularis mucosae Longitudinal muscle Circular muscle Connective tissue Epithelium (mesothelium)

13 © 2013 Pearson Education, Inc. Enteric Nervous System Intrinsic 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

14 © 2013 Pearson Education, Inc. Figure 23.7a Anatomy of the oral cavity (mouth). Palatoglossal arch Soft palate Hard palate Oral cavity Palatine tonsil Tongue Oropharynx Lingual tonsil Epiglottis Hyoid bone Laryngopharynx Esophagus Trachea Uvula Sagittal section of the oral cavity and pharynx

15 © 2013 Pearson Education, Inc. Figure 23.7b Anatomy of the oral cavity (mouth). Gingivae (gums) Palatine raphe Hard palate Soft palate Palatine tonsil Sublingual fold with openings of sublingual ducts Oral vestibule Lower lip Uvula Upper lip Superior labial frenulum Palatoglossal arch Palatopharyngeal arch Posterior wall of oropharynx Tongue Lingual frenulum Opening of Submandibular duct Gingivae (gums) Inferior labial frenulum Anterior view

16 © 2013 Pearson Education, Inc. Figure 23.8 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

17 © 2013 Pearson Education, Inc. Figure 23.9 The salivary glands. Tongue Teeth Frenulum of tongue Mylohyoid muscle (cut) Anterior belly of digastric muscle Masseter muscle Body of mandible (cut) Posterior belly of digastric muscle Serous cells forming demilunes Mucous cells Parotid gland Submandibular duct Submandibular gland Ducts of sublingual gland Sublingual gland Parotid duct

18 © 2013 Pearson Education, Inc. Salivary 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

19 © 2013 Pearson Education, Inc. 97–99.5% water, slightly acidic –Electrolytes—Na +, K +, Cl –, PO 4 2–, HCO 3 – –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 Composition of Saliva

20 © 2013 Pearson Education, Inc. Control of Salivation 1500 ml/day activated by parasympathetic when –Ingested 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

21 © 2013 Pearson Education, Inc.

22 Teeth Primary and permanent dentitions formed by age 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

23 © 2013 Pearson Education, Inc.

24 Figure Human dentition. Incisors Central (6–8 mo) Lateral (8–10 mo) Canine (eyetooth) (16–20 mo) Molars First molar (10–15 mo) 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 Deciduous (milk) teeth

25 © 2013 Pearson Education, Inc. Dental Formulas Shorthand indicator of number/position of teeth –Ratio of upper to lower teeth for 1/2 of mouth –Primary: –Permanent:

26 © 2013 Pearson Education, Inc. 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

27 © 2013 Pearson Education, Inc. Tooth 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

28 © 2013 Pearson Education, Inc. 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.

29 © 2013 Pearson Education, Inc. Figure Longitudinal section of a canine tooth within its bony socket (alveolus). Enamel Dentin Dentinal tubules Pulp cavity (contains blood vessels and nerves) Gingival sulcus Gingiva (gum) Cement Root canal Periodontal ligament Apical foramen Bone Crown Neck Root

30 © 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

31 © 2013 Pearson Education, Inc. Tooth and Gum Disease Gingivitis –Plaque calcifies to form calculus (tartar) –Calculus disrupts seal between gingivae and teeth –Bacteria infect gums

32 © 2013 Pearson Education, Inc. Tooth and Gum Disease Periodontitis -Immune cells attack Destroy periodontal ligament Activate osteoclasts  dissolve bone –Tooth loss; may promote atherosclerosis –Risk factors ?


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