external anal sphincter
Quick Summary
The external anal sphincter is a ring of voluntary muscle that encircles the outside of the anal canal and the anal opening. It is one of the two muscular constrictions that control the passage of feces. This sphincter is under voluntary control, meaning individuals can consciously contract or relax it, except during early childhood when it is still developing.12
The anal canal itself is the final section of the digestive tract, connecting the rectum to the anus. It is lined with skin-like tissue and contains both an internal, involuntary sphincter and the external, voluntary sphincter to regulate bowel movements. The external anal sphincter plays a crucial role in continence, allowing individuals to control the timing of defecation.13
Ask Britannica AI about this topic
Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.
- anal canal
The external sphincter is a layer of voluntary (striated) muscle encircling the outside wall of the anal canal and anal opening. One can cause it to expand and contract at will, except during the early years of life when it is not yet fully developed. Nerves…
Read MoreThe external sphincter is a layer of voluntary (striated) muscle encircling the outside wall of the anal canal and anal opening. One can cause it to expand and contract at will, except during the early years of life when it is not yet fully developed. Nerves…
Read More 
human digestive systemRectum and anusA second sphincter, the external anal sphincter, is composed of striated muscle and is divided into three parts known as the subcutaneous, superficial, and deep external sphincters. Thus, the internal sphincter is composed of smooth muscle and is innervated by the autonomic nervous system, while the external sphincters are…
Read MoreA second sphincter, the external anal sphincter, is composed of striated muscle and is divided into three parts known as the subcutaneous, superficial, and deep external sphincters. Thus, the internal sphincter is composed of smooth muscle and is innervated by the autonomic nervous system, while the external sphincters are…
Read More