Digestive System

Primary Structures of the Digestive Tract
1. Oral Cavity (S)
  1. Absorbs some (ex. ethanol, drugs) (F)
  2. Teeth (S)
    1. Mechanical Digestion (F)
  3. Tongue (S)
    1. Bolus formation (F)
    2. Activating food receptors (F)
  4. Salivary Glands (S)
  5. Hard and Soft Palates (S)
2. Pharynx (S)
  1. Activates swallowing center of medulla oblongata via bolus (F)
  2. Connects mouth to esophagus (F)
  3. Closes epiglottis during swallowing (F)
3. Esophagus (S)
  1. Upper Sphincter
  2. Lower Cardiac Sphincter
  3. Connects pharynx to stomach (F)
  4. Long musclar tube (2 smooth musc layers) (S)
    1. Inner annulated smooth muscle layer (S)
    2. Outer longitudinal smooth muscle layer (S)
    3. Top 1/3 = some skeletal muscle (S)
  5. Moves bolus to stomach via peristalsis (F)
4. Stomach (S)
  1. Regions of Stomach (S)
    1. Cardia (S)
      1. Connect esophagus to stomach (F)
    2. Fundus (S)
      1. Upper stomach curve (S)
    3. Body (S)
      1. Central stomach region (S)
      2. 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)
    4. Pylorus (S)
      1. The lower pt of stomach (S)
      2. Connects stomach to small intestine (F)
5. Small Intestine (S)
  1. Duodenum (S)
    1. Continues chemical digestion (F)
    2. Takes in bile and pancreatic secretions via Ampulla of Vater (F)
    3. Secretes GIP (F)
      1. With elevated glucose in chyme (F)
      2. Stimulates more insulin secretion (F)
  2. Jejunum (S)
    1. Most absorption here (F)
    2. Smooth muscle lining (S)
      1. Aids peristalsis (F)
      2. External segmentation (S)
  3. Ileum (S)
    1. Absorbs more bile, vitamins, and nutrients (F)
      1. Fat-Soluble Vitamins: ADEK Water-Soluble Vitamins: BC
    2. Shorter villi (S)
    3. Smaller diameter (S)
    4. Peyer's Patches (S)
      1. Lymph tissue patches (S)
      2. Prevents infection (F)
6. Large Intestine (S)
  1. Cecum (S)
    1. Vestigial appendix (S)
    2. Connects to small intestine via ileocecal valve (F)
  2. Colon (S)
    1. Ascending
    2. Transverse
    3. Descending
    4. Sigmoid
    5. Bac prod vitamins stored here (F)
  3. Rectum (S)
    1. Anus (S)
      1. Stores fecal matter (F)
      2. Anus
        Expels fecal matter (F)
Accessory Structures of the Digestive Tract
1. Pancreas (S)
  1. Exocrine gland
  2. Secretes hormones into the bloodstream (F)
    1. Insulin (S)
      1. Beta cell
    2. Glucagon (S)
      1. Alpha cell
    3. Somatostatin (S)
      1. Delta cell (S)
  3. Pancreatic Polypeptide (S)
  4. Acini (S)
    1. Islet of Langerhans (S)
    2. PP Cell (S)
      1. Prod pancreatic polypeptide (PP) (F)
    3. Acinar cell (S)
2. Liver (S)
  1. Hepatocytes (S)
3. Gallbladder
  1. Stores and concentrates liver bile (F)
4. Salivary Glands (S)
  1. Parotid Gland (S)
    1. 20% of Saliva (F)
    2. Stensen's Duct (S)
  2. Submandibular Gland (S)
    1. Prod 75% Saliva (F)
    2. Drains w/ Wharton's Duct (S)
  3. Sublingual Gland (S)
    1. 5% of Saliva (F)
  4. Produces saliva (F)
    1. Saliva = 98% Water + 2% Other (S)
      1. Other = Mucus, glycoproteins, enzymes & antibacterial agents (S)
        Salivary Amylase (S)
        Starch/Glycogen --> monosaccharides/disaccharides (F)
        Lingual Lipase (S)
      2. Allows taste, bolus formation, teeth cleaning, antibacterial props., mastication, and oral lubrication (F)
  5. Drain via ducts (MA)
  6. Aids in forming food bolus (F)
1) Ingestion (MA)
1. 2) Digestion
  1. 3) Absorption
    1. 4) Elimination
NS & Hormonal regulation (MA)
Three Phases (MA)
1. 1) Cephalic (MA)
  1. 2) Gastric
    1. 3) Intestinal
      1. Activated by chyme entry into duodenum (MA)
    2. Activated by stomach expansion and pH drop in stomach (MA)
  2. Activated by anticipation of food (MA)

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Digestive System

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	Created by Chinazor Okeke about 5 years ago