Summary: Physiology: Digestion

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• 1 Lecture 1: Digestive tract

• 1.1 Functions

• What are the functions of the digestive system?

  1. Ingestion
  2. Secretion of water, acids, buffers, enzymes
  3. Mixing and propulsion
  4. Digestion (mechanical, chemical, fermentative)
  5. Absorption (to blood/lymph)
  6. Defecation

• 1.2 Regulation

• How is the GI tract regulated?

  1. Intrinsically: local nervous and endocrine systems within the GI tract: Regulation of specific GIT functions
  2. Extrinsically: CNS, ANS, endocrine system: broad promotion or inhibition of GIT activity

• What are some GIT functions that are regulated intrinsically?

  Secretions, patterns of motility, reflexes

• What are some GIT functions that are regulated extrinsically?

  Fight or flight, rest and digest

• 1.3 ENS

• What are the networks of the ENS?

  1. Myenteric plexus: between circular and longitudinal muscle layers
  2. Submucosal plexus: within the submucosa

• What are the functions of the myenteric plexus?

  Control GI tract motility by providing motor inputs to muscle layers and by receiving sensory inputs from mechanoreceptors

• What are the functions of the submucosal plexus?

  Control GI secretions by providing motor inputs to smooth muscles of glands and by receiving sensory inputs from chemoreceptors in mucosa

• What coordinates the two plexuses of the ENS?

  Interneurons

• 1.3.1 Neurotransmitters

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• How do the nerves of the ENS communicate with the structures they innervate?

  Neurotransmitters

• What specialized structure do the motor axons of the ENS have?

  Arborizations called varicosities