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DIGESTIVE SYSTEM

Explore the various organs of the digestive system and their functions, from ingestion to defecation, including the layers of the alimentary canal and the anatomy of the mouth, stomach, and small intestine. Learn about the crucial role of the large intestine and the process of absorption.

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DIGESTIVE SYSTEM

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  1. DIGESTIVE SYSTEM

  2. Peritoneum: Membrane of the abdominal cavity • Parietal Peritoneum covers the abdominal wall • Visceral Peritoneum covers the inner organs Branching from the peritoneum: • Lesser omentum—attaches the liver to the lesser curvature of stomach • Greater omentum: (Apron) Contains fat to insulate, cushion, and protect abdominal organs

  3. The Digestive System Functions • Ingestion—taking in food • Digestion—breaking food down both physically and/or chemically • Absorption—movement of nutrients into the bloodstream • Defecation—rids the body of indigestible waste

  4. Organs of the Digestive System • Two main groups of organs • Alimentary canal (gastrointestinal or GI tract) -- continuous coiled hollow tube from mouth to anus • Accessory digestive organs -- aid in digestion but food does not pass through

  5. Layers of Alimentary Canal Organs • Four layers • Mucosa • Submucosa • Muscularis externa • Serosa

  6. Layers of Alimentary Canal Organs • Mucosa • Innermost, moist membrane , smooth muscle layer • Submucosa • Just beneath the mucosa, contains blood vessels and nerve endings • Muscularisexterna—smooth muscle • Inner circular layer and outer longitudinal layer • Serosa—outer membrane

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

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

  9. Mouth Physiology • Ingestion • Mastication (chewing) of food • Mixing masticated food with saliva • Initiation of swallowing by the tongue • Allows for the sense of taste • Enzymes from salivary glands are secreted here • Digestion begins here

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

  11. Pharynx Physiology • Serves as a passageway for air and food • Food is propelled to the esophagus by two muscle layers • Longitudinal inner layer • Circular outer layer • Food movement is by alternating contractions of the muscle layers (peristalsis) http://www.nlm.nih.gov/medlineplus/ency/anatomyvideos/000097.htm

  12. Esophagus Anatomy and Physiology • Anatomy • About 10 inches long • Runs from pharynx to stomach through the diaphragm • Physiology • Conducts food by peristalsis (slow rhythmic squeezing; a wave-like movement of smooth muscles) • Passageway for food only (respiratory system branches off after the pharynx)

  13. Stomach Anatomy • Located on the left side of the abdominal cavity • Food enters at the cardioesophageal sphincter • Contain Rugae—internal folds of the mucosa • Food empties into the small intestine at the pyloric sphincter (valve)

  14. Stomach Physiology • Temporary storage tank for food • Enzymes released here • Digestion occurs here • Hydrochloric Acid produced here • Delivers chyme (processed food) to the small intestine

  15. Subdivisions of the Small Intestine • Duodenum • Attached directly to the stomach • Jejunum • Attaches anteriorly to the duodenum • Ileum • End portion of the small intestine extends from jejunum to large intestine http://nutrition.jbpub.com/resources/animations.cfm?id=1&debug=0

  16. Small Intestine Anatomy • Structural modifications that increase surface area • Microvilli—tiny projections of the plasma membrane (create a brush border appearance) • Villi—fingerlike structures formed by the mucosa • Circular folds (plicae circulares)—deep folds of mucosa and submucosa

  17. Small Intestine Anatomy

  18. Large Intestine • No digestion here • Absorption occurs here • Larger in diameter, but shorter in length, than the small intestine • Frames the internal abdomen

  19. Large Intestine Anatomy • Cecum—saclike first part of the large intestine • Appendix • Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis) • Hangs from the cecum • Nursery for important digestive bacteria

  20. Large Intestine Anatomy • No villi present • Goblet cells produce alkaline mucus which lubricates the passage of feces • Muscularis externa layer is reduced to three bands of muscle called teniae coli • These bands cause the wall to pucker into haustra (pocketlike sacs) • Bacteria produce Vitamins

  21. Large Intestine Anatomy • Colon • Ascending—travels up right side of abdomen • Transverse—travels across the abdominal cavity • Descending—travels down the left side • Sigmoid—enters the pelvis • Rectum and anal canal—also in pelvis

  22. Large Intestine Anatomy • Anus—opening of the large intestine • Double sphincter • These sphincters are normally closed except during defecation

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