ABSTRACT
The following all contribute to the maintenance of anal continence:
• Internal anal sphincter activity, producing anal resting tone
• External anal sphincter activity, producing voluntary anal squeeze and reflex anal contraction when the rectum is initially distended
• Anorectal angle (which is normally less than 100 degrees)
• Anal sensation, including sampling reflex • Slit shape of anal canal • Vascular and mucosal components
Defaecation
• Requires relaxation of the anal sphincters (rectoanal inhibitory reflex)
• Varies with stool consistency (more difficult when stool is hard)
• Often follows a gastrocolic reflex (whole gut mass movement following eating and/or exercise)
• Normal frequency varies between twice per week to 3 times per day
“The bowels don’t need to empty every day!”
