1. PowerPoint ® Lecture Slides prepared by Barbara Heard, Atlantic Cape Community College C H A P T E R © 2013 Pearson Education, Inc.© Annie Leibovitz/Contact Press Images The Digestive System: Part A 23

2. © 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

3. © 2013 Pearson Education, Inc. Digestive System 2. Accessory digestive organs Teeth, tongue, gallbladder Digestive glands –Salivary glands –Liver –Pancreas

4. © 2013 Pearson Education, Inc. Figure 23.1 Alimentary canal and related accessory digestive organs. Mouth (oral cavity) Tongue* Esophagus Liver* Gallbladder* Small intestine Salivary glands* Pharynx Stomach Pancreas* Large intestine (Spleen) Parotid gland Sublingual gland Submandibular gland Duodenum Jejunum Ileum Anus Transverse colon Descending colon Ascending colon Cecum Sigmoid colon Rectum Appendix Anal canal

5. © 2013 Pearson Education, Inc. Digestive Processes Six essential activities 1.Ingestion 2.Propulsion 3.Mechanical breakdown 4.Digestion 5.Absorption 6.Defecation

6. © 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)

7. © 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.

8. © 2013 Pearson Education, Inc. GI Tract Regulatory Mechanisms 1.Mechanoreceptors and chemoreceptors –Respond to stretch, changes in osmolarity and pH, and presence of substrate and end products of digestion –Initiate reflexes that Activate or inhibit digestive glands Stimulate smooth muscle to mix and move lumen contents

9. © 2013 Pearson Education, Inc. GI Tract Regulatory Mechanisms 2.Intrinsic and extrinsic controls –Short reflexes - enteric nerve plexuses (gut brain) respond to stimuli in GI tract –Long reflexes respond to stimuli inside or outside GI tract; involve CNS centers and autonomic nerves –Hormones from cells in stomach and small intestine stimulate target cells in same or different organs to secrete or contract

10. © 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

11. © 2013 Pearson Education, Inc. Peritoneum and Peritoneal Cavity Peritoneum - serous membrane of abdominal cavity –Visceral peritoneum on external surface of most digestive organs –Parietal peritoneum lines body wall Peritoneal cavity –Between two peritoneums –Fluid lubricates mobile organs

12. © 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

13. © 2013 Pearson Education, Inc. Peritoneum and Peritoneal Cavity Mesentery - double layer of peritoneum –Routes for blood vessels, lymphatics, and nerves –Holds organs in place; stores fat Retroperitoneal organs posterior to peritoneum Intraperitoneal (peritoneal) organs surrounded by peritoneum

14. © 2013 Pearson Education, Inc. Homeostatic Imbalance Peritonitis –Inflammation of peritoneum –Causes by e.g., piercing abdominal wound, perforating ulcer, ruptured appendix –Peritoneal coverings stick together, localizing infection –Dangerous and lethal if widespread –Treated with debris removal and antibiotics

15. © 2013 Pearson Education, Inc. Blood Supply Hepatic portal circulation –Drains nutrient-rich blood from digestive organs –Delivers it to the liver for processing

16. © 2013 Pearson Education, Inc. Histology of the Alimentary Canal Four basic layers (tunics) –Mucosa –Submucosa –Muscularis externa –Serosa

17. © 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)

18. © 2013 Pearson Education, Inc. Mucosa Lines lumen Functions – different layers perform 1 or all 3 –Secretes mucus, digestive enzymes, and hormones –Absorbs end products of digestion –Protects against infectious disease Three sublayers: epithelium, lamina propria, and muscularis mucosae

19. © 2013 Pearson Education, Inc. Mucosa Epithelium –Simple columnar epithelium and mucus- secreting cells (most of tract) Mucus –Protects digestive organs from enzymes –Eases food passage –May secrete enzymes and hormones (e.g., in stomach and small intestine)

20. © 2013 Pearson Education, Inc. Mucosa Lamina propria –Loose areolar connective tissue –Capillaries for nourishment and absorption –Lymphoid follicles (part of MALT) Defend against microorganisms Muscularis mucosae: smooth muscle  local movements of mucosa

21. © 2013 Pearson Education, Inc. Submucosa –Areolar connective tissue –Blood and lymphatic vessels, lymphoid follicles, and submucosal nerve plexus

22. © 2013 Pearson Education, Inc. Muscularis Externa Muscularis externa –Responsible for segmentation and peristalsis –Inner circular and outer longitudinal layers Circular layer thickens in some areas  sphincters Myenteric nerve plexus between two muscle layers

23. © 2013 Pearson Education, Inc. Serosa Visceral peritoneum –Areolar connective tissue covered with mesothelium in most organs –Replaced by fibrous adventitia in esophagus –Retroperitoneal organs have both an adventitia and serosa

24. © 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)

25. © 2013 Pearson Education, Inc. Enteric Nervous System Intrinsic nerve supply of alimentary canal – enteric neurons (more than spinal cord) Major nerve supply to GI tract wall; control motility –Submucosal nerve plexus Regulates glands and smooth muscle in the mucosa –Myenteric nerve plexus Controls GI tract motility

26. © 2013 Pearson Education, Inc. Enteric Nervous System Linked to CNS via afferent visceral fibers Long ANS fibers synapse with enteric plexuses –Sympathetic impulses inhibit digestive activities –Parasympathetic impulses stimulate digestive activities

27. © 2013 Pearson Education, Inc. Functional Anatomy: Mouth Oral (buccal) cavity –Bounded by lips, cheeks, palate, and tongue –Oral orifice is anterior opening –Lined with stratified squamous epithelium

28. © 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

29. © 2013 Pearson Education, Inc. Lips and Cheeks Contain orbicularis oris and buccinator muscles Oral vestibule - recess internal to lips (labia) and cheeks, external to teeth and gums Oral cavity proper lies within teeth and gums Labial frenulum - median attachment of each lip to gum

30. © 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

31. © 2013 Pearson Education, Inc. Palate Hard palate - palatine bones and palatine processes of maxillae –Slightly corrugated to help create friction against tongue Soft palate - fold formed mostly of skeletal muscle –Closes off nasopharynx during swallowing –Uvula projects downward from its free edge

32. © 2013 Pearson Education, Inc. Digestive Processes: Mouth Ingestion Mechanical breakdown –Chewing Propulsion –Deglutition (swallowing) Digestion (salivary amylase and lingual lipase) ~ No absorption, except for few drugs

33. © 2013 Pearson Education, Inc. Mastication Cheeks and closed lips hold food between teeth Tongue mixes food with saliva; compacts food into bolus Teeth cut and grind Partly voluntary Partly reflexive –Stretch reflexes; pressure receptors in cheeks, gums, tongue

34. © 2013 Pearson Education, Inc. Deglutition Involves tongue, soft palate, pharynx, esophagus Requires coordination of 22 muscle groups Buccal phase –Voluntary contraction of tongue Pharyngeal-esophageal phase –Involuntary – primarily vagus nerve –Control center in the medulla and lower pons

35. © 2013 Pearson Education, Inc. Figure 23.13 Deglutition (swallowing). Bolus of food Tongue Pharynx Epiglottis Glottis Trachea During the buccal phase, the upper esophageal sphincter is contracted. The tongue presses against the hard palate, forcing the food bolus into the oropharynx. 1 Uvula Bolus Epiglottis Esophagus The pharyngeal-esophageal phase begins as the uvula and larynx rise to prevent food from entering respiratory passageways. The tongue blocks off the mouth. The upper esophageal sphincter relaxes, allowing food to enter the esophagus. The constrictor muscles of the pharynx contract, forcing food into the esophagus inferiorly. The upper esophageal sphincter contracts (closes) after food enters. Peristalsis moves food through the esophagus to the stomach. The gastroesophageal sphincter surrounding the cardial orifice opens, and food enters the stomach. Relaxed muscles Circular muscles contract Bolus of food Longitudinal muscles contract Gastroesophageal sphincter closed Relaxed muscles Circular muscles contract Gastroesophageal sphincter opens Upper esophageal sphincter Bolus 2 4 3 5 Stomach Slide 1

36. © 2013 Pearson Education, Inc. Figure 23.13 Deglutition (swallowing). Bolus of food Tongue Pharynx Epiglottis Glottis Trachea During the buccal phase, the upper esophageal sphincter is contracted. The tongue presses against the hard palate, forcing the food bolus into the oropharynx. 1 Slide 2

37. © 2013 Pearson Education, Inc. Figure 23.13 Deglutition (swallowing). Uvula Bolus Epiglottis Esophagus The pharyngeal-esophageal phase begins as the uvula and larynx rise to prevent food from entering respiratory passageways. The tongue blocks off the mouth. The upper esophageal sphincter relaxes, allowing food to enter the esophagus. 2 Slide 3

38. © 2013 Pearson Education, Inc. Figure 23.13 Deglutition (swallowing). The constrictor muscles of the pharynx contract, forcing food into the esophagus inferiorly. The upper esophageal sphincter contracts (closes) after food enters. Upper esophageal sphincter Bolus 3 Slide 4

39. © 2013 Pearson Education, Inc. Figure 23.13 Deglutition (swallowing). Peristalsis moves food through the esophagus to the stomach. Relaxed muscles Circular muscles contract Bolus of food Longitudinal muscles contract Gastroesophageal sphincter closed Stomach 4 Slide 5

40. © 2013 Pearson Education, Inc. Figure 23.13 Deglutition (swallowing). Peristalsis moves food through the esophagus to the stomach. Relaxed muscles Circular muscles contract Bolus of food Longitudinal muscles contract Gastroesophageal sphincter closed Stomach 4 Slide 5

41. © 2013 Pearson Education, Inc. Figure 23.13 Deglutition (swallowing). The gastroesophageal sphincter surrounding the cardial orifice opens, and food enters the stomach. Relaxed muscles Circular muscles contract Gastroesophageal sphincter opens 5 Slide 6

42. © 2013 Pearson Education, Inc. Figure 23.13 Deglutition (swallowing). Bolus of food Tongue Pharynx Epiglottis Glottis Trachea During the buccal phase, the upper esophageal sphincter is contracted. The tongue presses against the hard palate, forcing the food bolus into the oropharynx. 1 Uvula Bolus Epiglottis Esophagus The pharyngeal-esophageal phase begins as the uvula and larynx rise to prevent food from entering respiratory passageways. The tongue blocks off the mouth. The upper esophageal sphincter relaxes, allowing food to enter the esophagus. The constrictor muscles of the pharynx contract, forcing food into the esophagus inferiorly. The upper esophageal sphincter contracts (closes) after food enters. Peristalsis moves food through the esophagus to the stomach. The gastroesophageal sphincter surrounding the cardial orifice opens, and food enters the stomach. Relaxed muscles Circular muscles contract Bolus of food Longitudinal muscles contract Gastroesophageal sphincter closed Relaxed muscles Circular muscles contract Gastroesophageal sphincter opens Upper esophageal sphincter Bolus 2 4 3 5 Stomach Slide 7

43. © 2013 Pearson Education, Inc. Tongue Skeletal muscle Functions include –Repositioning and mixing food during chewing –Formation of bolus –Initiation of swallowing, speech, and taste Intrinsic muscles change shape of tongue Extrinsic muscles alter tongue's position Lingual frenulum: attachment to floor of mouth

44. © 2013 Pearson Education, Inc. Tongue Surface bears papillae –Filiform—whitish, give the tongue roughness and provide friction; do not contain taste buds –Fungiform—reddish, scattered over tongue; contain taste buds –Vallate (circumvallate)—V-shaped row in back of tongue; contain taste buds –Foliate—on lateral aspects of posterior tongue; contain taste buds that function primarily in infants and children

45. © 2013 Pearson Education, Inc. Tongue Lingual lipase –Secreted by serous cells beneath foliate and vallate papillae secrete –Fat-digesting enzyme functional in stomach

46. © 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

47. © 2013 Pearson Education, Inc. Salivary Glands Major salivary glands –Produce most saliva; lie outside oral cavity –Parotid –Submandibular –Sublingual Minor salivary glands –Scattered throughout oral cavity; augment slightly

48. © 2013 Pearson Education, Inc. Salivary Glands Function of saliva –Cleanses mouth –Dissolves food chemicals for taste –Moistens food; compacts into bolus –Begins breakdown of starch with enzymes

49. © 2013 Pearson Education, Inc. Salivary Glands Parotid gland –Anterior to ear; external to masseter muscle –Parotid duct opens into oral vestibule next to second upper molar –Mumps is inflammation of parotid glands

50. © 2013 Pearson Education, Inc. Salivary Glands Submandibular gland –Medial to body of mandible –Duct opens at base of lingual frenulum Sublingual gland –Anterior to submandibular gland under tongue –Opens via 10–12 ducts into floor of mouth

51. © 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

52. © 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

53. © 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 microorganisms PLAY Animation: Rotating head Composition of Saliva

54. © 2013 Pearson Education, Inc. Control of Salivation 1500 ml/day Intrinsic glands continuously keep mouth moist Major salivary glands activated by parasympathetic nervous system 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 Strong sympathetic stimulation inhibits salivation and results in dry mouth (xerostomia)

55. © 2013 Pearson Education, Inc. Teeth Tear and grind food for digestion 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

56. © 2013 Pearson Education, Inc. Classes of Teeth Incisors –Chisel shaped for cutting Canines –Fanglike teeth that tear or pierce Premolars (bicuspids) –Broad crowns, rounded cusps – grind/crush Molars –Broad crowns, rounded cusps – best grinders

57. © 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) 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

58. © 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

59. © 2013 Pearson Education, Inc. Tooth Structure Canine, incisor, and premolar  one root –First upper premolar often has two First two upper molars  three roots First two lower molars  two roots Third molar roots vary; often single fused root

60. © 2013 Pearson Education, Inc. Tooth Structure Cement - calcified connective tissue –Covers root; attaches it to periodontal ligament Periodontal ligament –Forms fibrous joint called gomphosis –Anchors tooth in bony socket Gingival sulcus - groove where gingiva borders tooth

61. © 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, blood vessels, and nerves Root canal - as pulp cavity extends to root Apical foramen at proximal end of root –Entry for blood vessels, nerves, etc.

62. © 2013 Pearson Education, Inc. Figure 23.11 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

63. © 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

64. © 2013 Pearson Education, Inc. Tooth and Gum Disease Gingivitis –Plaque calcifies to form calculus (tartar) –Calculus disrupts seal between gingivae and teeth –Anaerobic bacteria infect gums –Infection reversible if calculus removed

65. © 2013 Pearson Education, Inc. Tooth and Gum Disease Periodontitis (from neglected gingivitis) –Immune cells attack intruders and body tissues Destroy periodontal ligament Activate osteoclasts  dissolve bone –Possible tooth loss; may promote atherosclerosis and clot formation in coronary and cerebral arteries –Risk factors - smoking, diabetes mellitus, oral piercing