Neurological Aspects
When defecating, the external sphincter muscles relax. The anal and urethal sphincter muscles are closely linked, and experiments by Dr. Harrison Weed at the Ohio State University Medical Center have shown that they can be contracted only together, not individually, and that they both show relaxation during urination. This explains why defecation is frequently accompanied by urination, and why urination is frequently accompanied by flatulence.
Defecation may be involuntary or under voluntary control. Young children learn voluntary control through the process of toilet training. Once this has been achieved, loss of control causing fecal incontinence may be caused by physical injury – such as damage to the anal sphincter that may result from an episiotomy, intense fright, excessive pressure placed upon the abdomen, inflammatory bowel disease, impaired water absorption in the colon (diarrhea), and psychological or neurological factors.
The loss of voluntary control of defecation is experienced frequently by those undergoing a terminal illness.
Read more about this topic: Defecation
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