SURGERY RESIDENT BLOG

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What is the difference between the internal and external anal sphincters?

QUESTION: What is the difference between the internal and external anal sphincters?

ANSWER:

External sphincter (puborectalis muscle)
– under CNS (voluntary control)
– inferior rectal branch of internal udendal nerve and perineal branch of S4
– is the continuation of the levator ani muscle (striated muscle)

Internal sphincter
– involuntary control
– is the continuation of the circular band of colon muscle (smooth muscle)
– is normally contracted

NEXT QUESTION: What is the treatment for common bile duct stricture?

Source: The Absite Review, p.223

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