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THE DIGESTIVE SYSTEM The Digestive System The Digestive System The

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THE DIGESTIVE SYSTEM The Digestive System The Digestive System The Powered By Docstoc
					                                                                                                4/13/2011




                                                              The Digestive System
                                                   • Functions
                                                     –   Takes in food
          THE DIGESTIVE SYSTEM                       –   Breaks it down
                                                     –   Absorbs nutrients
                                                         Absorbs nutrients
                                                     –   Eliminates non‐digestible substances
                 THE FOOD PROCESSOR




            The Digestive System                              The Digestive System
• General Organization                             • Digestive Processes (Fig 23.2)
                                                     –   Ingestion
   – Alimentary canal (GI    Accessory Organs
     tract)                                          –   Propulsion – peristalsis
      •   Mouth                  ‐ Teeth
      •   Pharynx                ‐ Tongue            –   Mechanical digestion segmentation
                                                         Mechanical digestion –
      •   Esophagus
      •   Stomach
                                 ‐ Gallbladder       –   Chemical digestion
      •   Small Intestine      ‐ Salivary glands     –   Absorption
      •   Large Intestine      ‐ Liver
                                  ‐ Pancreas
                                                     –   Defecation




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           The Digestive System                                    The Digestive System
• Basic Functional concepts                              • Histology of the Alimentary Canal (Fig 23‐6)
                                                           – Mucosa
                                                              • Secretion                      Epithelium
  – Digestive activity is provoked by a range of              • Absorption                     Lamina Propria
    mechanical and chemical stimuli
    mechanical and chemical stimuli                           • Protection                     Muscularis mucosae
                                                           – Submucosa
  – Controls of digestive activity are both extrinsic         • Dense CT
    and intrinsic                                             • Blood and lymphatic vessels, lymphoid tissue, nerve 
                                                                fibers




           The Digestive System                                    The Digestive System
  – Muscularis Externa                                   • Nervous System Control
     • Segmentation – circular layer                       – Enteric Nervous System
     • Peristalsis – longitudinal layer                       • Submucosal plexus
                                                                     g                  y g
                                                                 – Regulates the activity of glands and muscle of mucosa
  – Serosa                                                    • Myenteric nerve plexus
     • Visceral peritoneum                                       – Located between smooth muscle layers of muscularis
                                                                 – Control GI motility
     • Outer covering
     • Adventitia around esophagus




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                                                                                The Digestive System
          The Digestive System                                                  Functional Anatomy
• Nervous System Control                                         • Mouth
  – Autonomic Control                                              –    teeth
     • Parasympathetic influence increases secretory activity      –    buccal cavity
       and motility
                                                                   –    lips and cheeks
                                                                        lips and cheeks
     • Sympathetic influence decreases digestive activities
                                                                   –    hard and soft palate with uvula
                                                                   –    tongue
                                                                   –    salivary glands – cleanse mouth, taste, moistens 
                                                                       food, chemical breakdown of CHO




              The Digestive System
              Functional Anatomy
                                                                             The Digestive System
• Pharynx                                                        • Esophagus (Fig 23‐12)
  – Oropharynx                                                     –   food tube
  – Laryngopharynx                                                 –   passes through esophageal or cardiac hiatus
                                                                   –   cardiac sphincter
                                                                       cardiac sphincter
                                                                   –   has all for histological layers 




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            The Digestive System                               The Digestive system
            Functional Anatomy                                 Functional Anatomy
• Digestive Processes of the mouth, pharynx,    • Stomach
  esophagus                                       –   chemical breakdown of proteins begin
                                                  –   food becomes creamy paste called chyme
  – M ti ti
    Mastication                                   –   Muscularis also has oblique layer
                                                      Muscularis also has oblique layer
  – Deglutination – swallowing                    –   Mucosa
  – Chemical diegstion                                • Gastric pits leading to gastric glands which make gastric 
                                                        juices
  – Propulsion
                                                      • Mucous cells, parietal glands (HCL), Chief cells 
                                                        (pepsinogen), enteroendocrine cells (hormones)




            The Digestive System                               The Digestive System
            Functional Anatomy                                 Functional Anatomy
• Digestive Processes of Stomach                • Small Intestine
  – Holding area                                  – begins just after pyloric sphincter of stomach to 
  – Mechanical and chemical breakdown               the ileocecal valve
  – Intrinsic factor absorption of B12
    Intrinsic factor – absorption of B12             complete digestion and all absorption
                                                  – complete digestion and all absorption
                                                  – 3 parts
                                                      • Duodenum
                                                      • Jejunum
                                                      • Ileum




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               The Digestive system
               Functional Anatomy
                                                                  The Digestive System
                                                       • Liver
 • Microscopic Anatomy of SI (Fig 23.22)
                                                         – Produces bile to digest fat
    – Circular folds
    – Villi                                              – Falciform ligament divides right and left lobes
       • Capillaries                                       Ligamentum teres is remnant of umbilical vein
                                                         – Ligamentum teres is remnant of umbilical vein
       • lacteals                                        – Organized in lobules  (refer to 23.24)
    – Microvilli
       • Brush border
       • Increase surface area




               The Digestive System                                  The Digestive System
               Functional Anatomy                                    Functional Anatomy
• Gall Bladder                                         • Digestive Processes of SI
  – Stores bile                                          –   3 to 6 hour journey thru SI
• Pancreas                                               –   Chemical digestion
    Produces enzymes for fat, CHO, protein digestion
  –P d                f f CHO           i di     i       –   Absorption
  – Main pancreatic duct and acessory pancreatic         –   Propulsion
    duct




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               The Digestive System                              The Digestive System
               Functional Anatomy                                Functional Anatomy
• Large Intestine                                   • Colon
  – 3 features                                        – Ascending colon
     • Teniae coli                                    – Transverse colon
     • Haustra                                          Descending colon
                                                      – Descending colon
     • Epiploic appendages
                                                      – Sigmoid colon
  – Subdivisions
     • Cecum, appendix, colon, rectum, anal canal




               The Digestive System                              The Digestive System
               Functional Anatomy                                Functional Anatomy
• Rectum (3rd sacral vertebra)                      • Bacterial Flora
  – rectal valves
• Anal canal                                          – Bacteria entering from small intestine and from 
  – entirely external to abdominopelvic cavity
       i l          l     bd i       l i   i            anus constitute flora
                                                        anus constitute flora
  – involuntary internal anal sphincter               – Ferment some indigestible CHO
  – voluntary external anal sphincter                 – Synthesize B complex vitamins and vitamin K




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              The Digestive System
              Functional Anatomy
                                                                   Clinical Conditions
• Digestive Processes                                • Enteritis
   – 12‐ 24 hours thru large intestine
   – Absorption of water                               – Inflammation of the mucosa and submucosa of 
   – Defecation                                          the intestine
                                                         the intestine
                                                       – Caused by radiation
                                                       – Crohn’s disease
                                                       – Alcohol




             Clinical Conditions                                   Clinical Conditions
• Diverticulitis                                     • Irritable bowel syndrome
   – Inflammation of a diverticulum which is an        – Disturbance of intestinal function of unknown 
     outpouching of the large intestinal wall            cause
      Feces stagnates in diverticulum can lead to 
   – Feces stagnates in diverticulum can lead to         Intermittent symptoms of abdominal discomfort, 
                                                       – Intermittent symptoms of abdominal discomfort
     infection                                           cramping, altered bowel activity
   – Pain                                              – No fever or weight loss




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