digestive system 2

• Fistula


  A hole in the abdominal wall that allowed a view into the stomach
• Beaumont's experiments on St. Martin

  1. Recorded what St. Martin ate and what his stomach did to the meals

  2. Shoved food tied to a string into St. Martin's gut-hole

  3. Took samples of gastric juices and had them analyzed
• Beaumont's findings


  • The stomach's extremely strong acids and muscular contractions break down food
  • Some foods are more digestible or less digestible than others
  • The brain can affect the stomach
• Digestion


  The mechanical and chemical breakdown of food
• Oral/buccal cavity


  Where digestion starts, through chewing and enzyme-action
• Mouth


  • Lined with tough, thick stratified squamous epithelium
  • Anterior hard palate and posterior soft palate form the roof
  • Hard palate provides a hard surface for the tongue, soft palate closes off the nasopharynx when swallowing
• Teeth


  • Roughly 32 of them, in basic types that help masticate (chew) food
• Tongue


  A big muscle that grips and repositions food as it is chewed
• Bolus


  The ball of mashed food
• Salivary glands


  Three major pairs that churn out an average of 1.5 liters of slightly acidic saliva per day
• Salivary amylase


  A digestive enzyme that breaks down starches into glucose monomers
• Pharynx


  Where the bolus is propelled into the esophagus by peristalsis
• Esophagus


  A glorified laundry chute lined with smooth muscle, that transports the bolus to the stomach
• Stomach


  The stretchiest part of the digestive tube, capable of holding 2 to 4 liters of material
• Stomach


  • Has an additional layer of smooth muscle that gives it extra strength to actively smush food around
  • Inner mucosa is made up almost entirely of mucous cells that produce a protective coat
• Gastric pits and glands


  Contain various types of secretory cells that produce hydrochloric acid, pepsinogen, and regulatory hormones
• Hydrochloric acid


  A substance more acidic than battery acid, that denatures proteins and kills bacteria/viruses
• Pepsin


  A protein-digesting enzyme created when hydrochloric acid is combined with pepsinogen
• Enteroendocrine cells


  Release regulatory hormones like serotonin, histamine, and somatostatin to control stomach activity
• 1. cells


  Produce the hormone gastrin, which stimulates gastric secretions and muscle activity
• Gastric regulation


  1. Cephalic phase (brain-controlled)

  2. Gastric phase (stomach-controlled)

  3. Intestinal phase (small intestine-controlled)
• Cephalic phase


  Triggered by seeing, smelling, tasting, or thinking about food, stimulating the stomach via the vagus nerve
• Gastric phase


  Triggered by food entering the stomach, activating stretch receptors and secretion of gastrin
• Intestinal phase


  Speeds or slows the rate of stomach emptying to prevent overloading the small intestine
• Chyme


  The creamy paste that the stomach turns food into
• Vomiting


  The stomach's urge to purge, triggered by ingesting too much food, irritants, toxins, or emotional/stress factors
• Beaumont noticed St. Martin's digestion was affected by illness or stress, demonstrating the mind-stomach connection