GI Motility Patterns

Overview
  • Two basic patterns of movement in the GI tract are responsible for propulsion and mixing of GI contents, termed "Peristalsis" and "Mixing Movements", respectively. We discuss the general phenomenological features of these movements in this page although their electrical basis is likely that described in Electrical Basis of GI Rhythmic Contractions.
Peristalsis
  • Definition
    • Peristalsis is a pattern of GI motility which propels GI contents unidirectionally, generally toward the Anus.
  • Physical Basis
    • Peristalsis is generally initiated by distension of a particular segment of the GI tract. Distention initiates contraction of a ring of muscle several centimeters behind the bolus, thus pushing the bolus anally. Additionally, distention induces alimentary segments several centimeters in front of the bolus to relax, facilitating its forward movement.
  • Regulatory Basis
Mixing Movements
  • Definition
    • Mixing movements are a pattern of GI motility that helps to mix and churn GI contents.
  • Physical Basis
    • Some mixing is achieved by performing peristalsis against a closed sphincter and this is the primary basis of mixing in the stomach (See: Gastric Motility). In other cases, a contractile rings occur intermittently at random segments throughout a section of the GI tract. This pattern, referred to as "Segmentation", effectively chops the GI contents, thus mixing it without moving it in any particular direction.
  • Regulatory Basis
    • Coordination of mixing movements is achieved by the myenteric plexus. However, the autonomic nervous system can modulate the amount of mixing movements, with the parasympathetic nervous system generally enhancing mixing and the sympathetic system generally displaying an inhibitory effect.