The ileocolonic sphincter.
The human ileocolonic sphincter (ICS) develops a sustained tone mainly due to propagated and not propagated phasic motor activity. The ileocaecocolonic segment is also able to behave, yet uncommonly, as a synchronized segment involving propagated contractions originating from the ileum and migrating to the proximal colon. The ICS motor activity alone has a limited role towards forward flow. On the contrary, the functional entity corresponding to the distal ileum and the ICS provides a clearance mechanism for reflux of colonic contents into the small intestine. The presence of short chain fatty acids (SCFA) in the distal ileum, sensed either by endocrine cells or chemo-sensitive vagal afferents, is an important actor in triggering this clearance mechanism. The ICS tone is in part myogenic but a neuronal nitrergic component is also involved. Reflex excitatory and inhibitory responses of the ICS originating from ileal or colonic distension involve primarily spinal nitrergic and adrenergic pathways.
Malbert
C-H
CH
UMRVP, INRA, France.
D000818:Animals; D003106:Colon / Q000033:anatomy & histology / Q000502:physiology; D005769:Gastrointestinal Motility / Q000502:physiology*; D006801:Humans; D007080:Ileocecal Valve / Q000033:anatomy & histology* / Q000502:physiology*; D007082:Ileum / Q000033:anatomy & histology / Q000502:physiology