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Chapter 14 The Digestive System and Body Metabolism

Chapter 14 The Digestive System and Body Metabolism. Digestive System & Body Metabolism. Digestion Breakdown of ingested food Absorption of nutrients into blood Metabolism Production of cellular energy (ATP) Constructive and degradative activities. Organs of the Digestive System.

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Chapter 14 The Digestive System and Body Metabolism

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  1. Chapter 14The Digestive System and Body Metabolism

  2. Digestive System & Body Metabolism • Digestion • Breakdown of ingested food • Absorption of nutrients into blood • Metabolism • Production of cellular energy (ATP) • Constructive and degradative activities

  3. Organs of the Digestive System Two main groups • Alimentary canal – continuous hollow tube • Accessory digestive organs

  4. Organs of the Alimentary Canal • Mouth • Pharynx • Esophagus • Stomach • Small intestine • Large intestine • Anus

  5. Mouth (Oral Cavity) Anatomy • Lips (labia) – protect • Cheeks – form lateral walls • Hard palate – forms anterior roof • Soft palate – forms posterior roof • Uvula – fleshy projection of the soft palate

  6. Mouth (Oral Cavity) Anatomy • Vestibule – space between lips & teeth and gums • Oral cavity – area contained by teeth • Tongue – attached at hyoid and styloid processes of the skull, and by the lingual frenulum • Tonsils – Palatine & Lingual

  7. Processes of the Mouth • Mastication (chewing) of food • Mixing food with saliva • Start swallowing using tongue • Sense of taste

  8. Layers of Alimentary Canal Organs Mucosa - Moist membrane • Surface epithelium • connective tissue (lamina propria) • Small smooth muscle layer Submucosa - under mucosa • connective tissue with blood vessels, nerve endings, and lymphatics Muscularis externa – smooth muscle • Inner circular layer & Outer longitudinal layer Serosa - Outermost layer – visceral peritoneum • Layer of serous fluid-producing cells

  9. Alimentary Canal Nerve Plexuses • Autonomic nervous system • Three networks of nerve fibers • Submucosal nerve plexus • Myenteric nerve plexus • Subserous plexus

  10. Pharynx Anatomy • Nasopharynx – not part of the digestive system • Oropharynx – posterior to oral cavity • Laryngopharynx – below the oropharynx and connected to the esophagus

  11. Pharynx Function • Passageway for air and food • Food moved by peristalsis • alternating contractions of muscle layers • Longitudinal inner layer • Circular outer layer

  12. Esophagus • From pharynx to stomach through diaphragm • Moves food by peristalsis • Food only

  13. Stomach Anatomy • Left side of abdomen • Food enters at cardioesophageal sphincter • Regions • Cardiac region – near the heart • Fundus • Body • Phylorus – funnel-shaped terminal end • Food empties into the small intestine at the pyloric sphincter • Rugae – internal folds of the mucosa

  14. Stomach Anatomy • External regions • Lesser curvature • Greater curvature • Layers of peritoneum attached to the stomach • Lesser omentum – attaches liver to lesser curvature • Greater omentum – attaches greater curvature to posterior body wall • fat insulates, cushions, protects

  15. Stomach Functions • Storage tank for food • Physical breakdown • Chemical breakdown of protein begins • Delivers chyme (processed food) to the small intestine

  16. Specialized Mucosa of the Stomach Simple columnar epithelium • Mucous neck cells – produce a sticky alkaline mucus • Gastric glands – secrete gastric juice • Chief cells – produce protein-digesting enzymes (pepsinogens) • Parietal cells – produce hydrochloric acid • Endocrine cells – produce gastrin • Gastric pits formed by folded mucosa • Glands and specialized cells are in the gastric gland region

  17. Small Intestine • Major digestive organ • Nutrient absorption • From pyloric sphincter to ileocecal valve • Suspended from abdominal wall by mesentery • 3 parts: • Duodenum - curves around pancreas • Jejunum • Ileum

  18. Chemical Digestion in the Small Intestine • Source of enzymes that are mixed with chyme • Intestinal cells • Pancreas • Bile enters from the gall bladder

  19. Villi of Sm. Intestine Microvilli of Sm. Intestine • Fingerlike structures formed by mucosa • Give intestine more surface area • Small projections of plasma membrane • Found on absorptive cells

  20. Large Intestine • Wider, but shorter,frames the abdomen • Cecum – saclike first part • Appendix - Hangs from the cecum • Colon • Ascending • Transverse • Descending • S-shaped sigmoidal • Rectum • Anus – external body opening

  21. Functions of the Large Intestine • Absorbs of water • Eliminates feces – indigestible food • No digestion • Goblet cells produce mucus as lubricant

  22. Modifications to the Muscularis Externa in the Large Intestine • Smooth muscle is reduced to three bands (teniae coli) • Muscle bands have some degree of tone • Walls formed into pocketlike sacs called haustra

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