Spastic contraction of anal canal sphincter

Spasmodic contraction of and sphincter is also known as sphincter sphincter. Under normal circumstances, dilatation of the rectum or rectal sigmoid colon can immediately cause reflex relaxation of the internal anal sphincter (IAS). This reflex is called the rectal sphincter relaxation reflex, or the rectal inhibitory reflex, and is important for defecation. If the IAS is spastic and cannot relax, it will cause obstructive constipation at the exit.