Abdominal Anatomy


Abdominal Anatomy, Abdomen, Gastrointestinal Anatomy, Gastrointestinal System, Digestive System, Gastrointestinal Tract, GI Tract, Alimentary Tract, Digestive Tract

  • Physiology
  • Gastrointestinal Motility
  1. Chewing (mastication)
    1. Chewing breaks apart food for greater surface area, allowing for later processing and absorption
    2. Nerve control: CN 5 (Trigeminal Nerve)
    3. Muscles of Mastication
      1. Masseter Muscle
      2. Temporalis Muscle
      3. Lateral Pterygoid Muscle
      4. Medial Pterygoid Muscle
  2. Swallowing
    1. See Swallowing
    2. See Dysphagia
    3. Oropharyngeal Stage
      1. Food bolus is created and moved to the posterior pharynx, propelled by the Tongue
      2. Food passes ino the esophagus, with the airway protected from aspiration
      3. Nerve control: CN 5, CN 9, CN 10 and CN 12
      4. Saliva and mucus lubricates food for easier transit
    4. Esophageal Stage
      1. See Achalasia
      2. Esophageal mucus (produced by mucous cells) lubricates the esophagus for food transit
      3. Nerve Control: CN 10
        1. Voluntary control in upper third of esophagus
        2. Involuntary, autonomic control in the lower esophagus
  3. Peristalsis
    1. See Ileus
    2. Peristalsis propels food from the Stomach forward through the intestinal tract
    3. Timing
      1. Solid Food exits the Stomach after 1-3 hours
      2. Food exits the Small Intestine (at the ileocecal valve) after 4-6 hours
      3. Food exits the colon with Defecation typically after 1-2 days
    4. Nerve Control: CN 10 (Vagal Nerve)
      1. Stimulates peristalsis
        1. Myenteric Plexus (Auerbach's plexus) between the bowel's circular and longitudinal Muscles
      2. Relaxes sphincters
      3. Promotes glandular secretion
        1. Meissner's Plexus in the submucosal layer
  • Physiology
  • Digestion Mediators
  1. Mouth
    1. Salivary Amylase
      1. Breaks down starches (to maltose and other sugars)
  2. Stomach
    1. Background
      1. Stomach mucosa is exposed to low pH (HCl) and digestive enzymes (e.g. pepsin)
      2. Stomach mucosa is protected by mucus (from mucous neck cell) and bicarbonate (from epithelial cells)
    2. Pepsinogen
      1. Cleaves proteins to peptides
      2. Released by chief cell
      3. Activated to pepsin, triggered by Gastrin and Stomach acid
    3. Hydrochloric Acid (HCL)
      1. Breaks down starches
      2. Aids in mineral absorption and bacterocidal activity
      3. Released by parietal cells
      4. Triggered by Vagus Nerve, Gastrin, histamine and proteins within the Stomach
    4. Intrinsic Factor
      1. Facilitates Vitamin B12 absorption from Small Intestine
      2. Released by parietal cells
      3. Triggered by Stomach and duodenal distention
      4. Suppressed by low gastric pH and intestinal fat
    5. Gastrin
      1. Stimulates HCl acid secretion by parietal cells and enzyme secretion from Pancreas
      2. Also increases peristalsis and relaxes pyloric sphincter and ileocecal valve
      3. Released from Gastrin cells in Stomach antrum
      4. Stimulated by Vagus Nerve, duodenal distention and proteins within the Stomach
      5. Suppressed by secretin, gastric inhibitory polypeptide and decreased Stomach pH
  3. Small Intestine
    1. Background
      1. Intestinal mucosa is protected by an alkaline mucus (from Brunner's Glands)
      2. Epithelial cells in Crypts of Lieberkuhn (within intestinal villi)
        1. Release most intestinal digestive enzymes (aside from Pancreatic Enzymes)
        2. Stimulated by Vagus Nerve and direct contact with food
    2. Carbohydrate digestion
      1. Maltase
        1. Cleaves maltose into two Glucose molecules
      2. Lactase
        1. Cleaves lactose into Glucose and galactose
      3. Sucrase
        1. Cleaves sucrose into Glucose and fructose
    3. Protein digestion
      1. Peptidases
        1. Cleaves peptides into amino acids
      2. Enterokinase
        1. Activates trypsinogen to trypsin
        2. Activates chymotrypsinogen to chymotrypsin
        3. Activates procarboxypolypetidase to carboxypolypetidase
    4. Fat and Cholesterol digestion
      1. Intestinal Lipase
        1. Metabolizes lipids to glycerol and Fatty Acids
      2. Intestinal esterases
        1. Metabolize Cholesterol esters to free Cholesterol and Fatty Acids
    5. Other enzymes
      1. Secretin
        1. Decreases Gastrin secretion
        2. Decreases intestinal motility
        3. Promotes bile acid secretion from liver
        4. Promotes bicarbonate secretion from Pancreas
      2. Gastric inhibitory peptide (GIP)
        1. Decreases Gastrin secretion
        2. Decreases gastric emptying
      3. Cholecystokinin
        1. Decreases gastric motility
        2. Promotes Pancreatic Enzyme and bicarbonate secretion
        3. Promotes Gall Bladder contraction and sphincter of oddi relaxation (intestinal bile acid secretion)
        4. Vasodilates intestinal mucosa vessels
      4. Bulbogastrone
        1. Suppresses acid secretion from gastric parietal cells
  4. Pancreas
  5. Liver and Gallbladder
  • Anatomy
  • Images
  1. giQuadrantsGrayBB1034.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  2. giQuadrantsGrayBB1220.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  3. giMarginsGrayBB1223.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  4. giMarginsGrayBB1224.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  5. giMarginsGrayBB1226.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  6. giAbdTrasverseXsL1GrayBB1097.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  7. giPeritoneumUpperAbdXsGrayBB1039.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  8. giPeritoneumLowAbdXsGrayBB1038.gif Lewis (1918) Gray's Anatomy 20th ed (in public domain at Yahoo or BartleBy)
  • References
  1. Goldberg (2014) Clinical Physiology, Medmasters, Miami, p. 120-31