Digestive System

Digestive System

1. Primary Structures of the Digestive Tract

   • Oral Cavity (S)
     • Absorbs some (ex. ethanol, drugs) (F)
     • Teeth (S)
       • Mechanical Digestion (F)
     • Tongue (S)
       • Bolus formation (F)
       • Activating food receptors (F)
     • Salivary Glands (S)
     • Hard and Soft Palates (S)
   • Pharynx (S)
     • Activates swallowing center of medulla oblongata via bolus (F)
     • Connects mouth to esophagus (F)
     • Closes epiglottis during swallowing (F)
   • Esophagus (S)
     • Upper Sphincter
     • Lower Cardiac Sphincter
     • Connects pharynx to stomach (F)
     • Long musclar tube (2 smooth musc layers) (S)
       • Inner annulated smooth muscle layer (S)
       • Outer longitudinal smooth muscle layer (S)
       • Top 1/3 = some skeletal muscle (S)
     • Moves bolus to stomach via peristalsis (F)
   • Stomach (S)
     • Regions of Stomach (S)
       • Cardia (S)
         • Connect esophagus to stomach (F)
       • Fundus (S)
         • Upper stomach curve (S)
       • Body (S)
         • Central stomach region (S)
         • Rugae (S)
           • Gastric glands (S)
             • Gastric pit (S)
               • Entrance to gastric glands (S)
             • Goblet (mucus) cells (S)
               • Produce mucus (F)
                 • Prevent peptic ulcers (F)
                 • 95% water + 5% mucus & bicarbonate (S)
             • Chief cells (S)
               • Secretes pepsinogen (F)
                 • To autocleave into pepsin w/ HCl secretion (F/MA)
                   • 1) Pepsinogen unfolds (MA)
                     • 2) Self-cleaves 44 AA from itself (MA)
                       • 3) Pepsin forms (MA)
                         • 4) Pepsin cleaves other pepsinogens
                         • Digests 20% of proteins (F)
                           • Cuts before hydrophobic AAs (F)
                             • Hydrophobic AAs: GALVIM
             • Parietal cells (S)
               • Produce HCl (F/MA)
                 • 1) CO2 moves into parietal cell via basolateral membrane (MA)
                   • 2) CO2 combines w/ H2O to form H2CO3 (MA)
                     • 3) H2CO3 dissociates into H+ and HCO3- (MA)
                       • 4) H+ moves into the lumen via K+/H+ antiporter at apical membrane (MA)
                         • 5) HCO3- moves into blood via HCO3-/Cl- antiporter (MA)
                           • 6) Cl- diffuses down gradient into lumen via gastric glands (MA)
                 • Kills microbial agents Denatures proteins (F)
             • G cells (S)
               • Prod gastrin (F)
                 • Regulates peristalsis, HCl & pepsinogen secretion (F)
             • D cells (S)
               • Prod somatostatin (F)
                 • Inhibits digestion (F)
                   • Lowers gastric emptying (F)
                   • Reduces peristalsis (F)
                   • Reduces blood flow (F)
                   • Suppresses pancreat
                 • Suppresses gastrin, CCK, and secretin (F)
       • Pylorus (S)
         • The lower pt of stomach (S)
         • Connects stomach to small intestine (F)
   • Small Intestine (S)
     • Duodenum (S)
       • Continues chemical digestion (F)
       • Takes in bile and pancreatic secretions via Ampulla of Vater (F)
       • Secretes GIP (F)
         • With elevated glucose in chyme (F)
         • Stimulates more insulin secretion (F)
     • Jejunum (S)
       • Most absorption here (F)
       • Smooth muscle lining (S)
         • Aids peristalsis (F)
         • External segmentation (S)
     • Ileum (S)
       • Absorbs more bile, vitamins, and nutrients (F)
         • Fat-Soluble Vitamins: ADEK Water-Soluble Vitamins: BC
       • Shorter villi (S)
       • Smaller diameter (S)
       • Peyer's Patches (S)
         • Lymph tissue patches (S)
         • Prevents infection (F)
   • Large Intestine (S)
     • Cecum (S)
       • Vestigial appendix (S)
       • Connects to small intestine via ileocecal valve (F)
     • Colon (S)
       • Ascending
       • Transverse
       • Descending
       • Sigmoid
       • Bac prod vitamins stored here (F)
     • Rectum (S)
       • Anus (S)
         • Stores fecal matter (F)
         • Anus
           • Expels fecal matter (F)

2. Accessory Structures of the Digestive Tract

   • Pancreas (S)
     • Exocrine gland
     • Secretes hormones into the bloodstream (F)
       • Insulin (S)
         • Beta cell
       • Glucagon (S)
         • Alpha cell
       • Somatostatin (S)
         • Delta cell (S)
     • Pancreatic Polypeptide (S)
     • Acini (S)
       • Islet of Langerhans (S)
       • PP Cell (S)
         • Prod pancreatic polypeptide (PP) (F)
       • Acinar cell (S)
   • Liver (S)
     • Hepatocytes (S)
   • Gallbladder
     • Stores and concentrates liver bile (F)
   • Salivary Glands (S)
     • Parotid Gland (S)
       • 20% of Saliva (F)
       • Stensen's Duct (S)
     • Submandibular Gland (S)
       • Prod 75% Saliva (F)
       • Drains w/ Wharton's Duct (S)
     • Sublingual Gland (S)
       • 5% of Saliva (F)
     • Produces saliva (F)
       • Saliva = 98% Water + 2% Other (S)
         • Other = Mucus, glycoproteins, enzymes & antibacterial agents (S)
           • Salivary Amylase (S)
             • Starch/Glycogen --> monosaccharides/disaccharides (F)
           • Lingual Lipase (S)
         • Allows taste, bolus formation, teeth cleaning, antibacterial props., mastication, and oral lubrication (F)
     • Drain via ducts (MA)
     • Aids in forming food bolus (F)

3. 1) Ingestion (MA)

   • 2) Digestion
     • 3) Absorption
       • 4) Elimination

4. NS & Hormonal regulation (MA)

5. Three Phases (MA)

   • 1) Cephalic (MA)
     • 2) Gastric
       • 3) Intestinal
         • Activated by chyme entry into duodenum (MA)
       • Activated by stomach expansion and pH drop in stomach (MA)
     • Activated by anticipation of food (MA)

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