Exam 5

• GI tract (alimentary tract)


  Muscular tube from the oral cavity to the anus
• Path of food


  1. Oral cavity

  2. Pharynx

  3. Esophagus

  4. Stomach

  5. Small intestine

  6. Large intestine
• Functions of the digestive system


  • Ingestion
  • Propulsion
  • Mechanical digestion
  • Secretion
  • Chemical digestion
  • Absorption
  • Defecation
• Visceral peritoneum (serosa)


  Covers organs
• Parietal peritoneum


  Lines the inner surface of the abdominal cavity
• Peritoneal fluid


  In peritoneal cavity between the 2 membranes which provide lubrication, reduces friction
• Buildup of peritoneal fluid

  Causes abdominal swelling
• Ascites


  Type of reaction caused by buildup of peritoneal fluid
• Mesenteries and their functions


  • Lesser omentum (stabilizes stomach)
  • Greater omentum (protects abdominal organs)
  • Mesentery proper (stabilizes small intestines)
  • Falciform ligament (stabilizes liver)
  • Mesocolon (stabilizes the large intestines)
• Layers of tissue: mucosa, submucosa, muscularis externa, serosa (visceral peritoneum)
• Mucosa


  Innermost layer, contains epithelium, lamina propria, muscularis mucosae
• Submucosa


  Composed of dense irregular connective tissue with blood & lymphatic vessels, submucosal glands
• Muscularis externa


  2 layers of smooth muscle involved with food propulsion, inner circular & outer longitudinal layers
• Serosa


  Visceral peritoneum, simple squamous epithelium & loose connective tissue form the outermost layer
• Peristalsis


  Muscle contractions that propel food forward
• Segmentation


  Mechanical processing by mixing in intestines, no forward movement
• Local factors that affect digestive functions include pH, stretch, protein content
• Chemical messengers


  Coordinate responses, e.g. histamine stimulates acid secretion in stomach
• Short reflexes


  Neural control by enteric nervous system, regulates motility & secretion independently of CNS
• Long reflexes


  Motility & secretions regulated by ANS, sympathetic inhibits parasympathetic
• Anatomy of oral cavity


  • Oral mucosa
  • Teeth
  • Tongue
  • Salivary glands
• Bolus


  Moist chewed mass of ingested food
• Functions of oral cavity


  • Sensory analysis
  • Mechanical digestion
  • Lubrication
  • Initial chemical digestion
• Some drugs can be absorbed sublingually, this is the fastest way for dry delivery
• Functions of tongue


  • Mechanical processing
  • Chewing & swallowing
  • Sensory analysis
  • Secretion of lingual lipase
• Types of teeth


  • Incisors
  • Canines
  • Premolars
  • Molars
• Lingual lipase


  Enzyme that digests triglycerides into glyceride fatty acids
• Components of saliva


  • Water
  • Electrolytes
  • Enzymes
  • Mucus
  • Other solutes
• Functions of saliva


  • Moistening & lubricating
  • Dissolving chemicals
  • Initiating chemical digestion
  • Preventing bacterial growth
• Types of salivary glands


  • Parotid gland
  • Sublingual gland
  • Submandibular gland
• Pharynx


  Shared passageway with respiratory system, throat
• Esophageal sphincters


  • Upper esophageal sphincter
  • Gastroesophageal sphincter
• Upper esophageal sphincter


  At the beginning of esophagus
• Gastroesophageal sphincter


  At the end of esophagus, prevents backflow
• Phases of swallowing


  • Voluntary (oral) phase
  • Pharyngeal phase
  • Esophageal phase
• Voluntary (oral) phase


  Tongue pushes bolus into oropharynx
• Pharyngeal phase


  Bolus enters oropharynx, soft palate & epiglottis seal off nasopharynx & larynx, respiratory centers inhibited, controlled by swallowing reflex
• Esophageal phase


  Upper esophageal sphincter relaxes, peristaltic wave pushes bolus toward stomach
• Voluntary (oral) phase is the voluntary phase, pharyngeal and esophageal phases are involuntary
• Anatomy of stomach


  • Lesser curvature
  • Greater curvature