1.1 Physiological Anatomy of GI Wall

• What are the layers of the intestinal wall from outer to inner?

  Serosa, longitudinal muscle, circular muscle, submucosa, mucosa
• What is the role of the mucosal muscle in the intestinal wall?

  It aids in the motor functions of the gut
• How long are individual smooth muscle fibers in the gastrointestinal tract?

  200 to 500 micrometers
• What is the diameter range of smooth muscle fibers in the gastrointestinal tract?

  2 to 10 micrometers
• How are the smooth muscle fibers arranged in the gastrointestinal tract?

  In bundles of up to 1000 parallel fibers
• What allows electrical signals to travel between muscle fibers in the gastrointestinal tract?

  Gap junctions connecting the muscle fibers
• How does the speed of electrical signal travel differ within a muscle bundle?

  Faster along the length than sideways
• What separates each bundle of smooth muscle fibers?

  Loose connective tissue
• What is a syncytium in the context of smooth muscle layers?

  A muscle layer that functions as a single unit
• What happens when an action potential is elicited in the muscle mass?

  It travels in all directions within the muscle
• What factors influence how far an action potential travels in the muscle?


  The excitability of the muscle
• What can happen to the distance an action potential travels?

  It can vary from a few millimeters to many centimeters
• How do the longitudinal and circular muscle layers interact?

  Excitation of one often excites the other