External anal sphincter

Definition

The external anal sphincter is a voluntary muscle that surrounds the anal canal and is responsible for controlling the expulsion of feces from the body. This muscle plays a crucial role in maintaining fecal continence, working in conjunction with the internal anal sphincter, which is involuntary. Its ability to contract and relax allows individuals to control bowel movements, providing a critical function in the gastrointestinal system.

5 Must Know Facts For Your Next Test

1. The external anal sphincter is under conscious control, allowing individuals to decide when to release feces.
2. In addition to its primary role in defecation, the external anal sphincter also helps maintain continence during activities that increase abdominal pressure, like coughing or sneezing.
3. Damage or weakening of the external anal sphincter can lead to fecal incontinence, a condition that significantly affects quality of life.
4. The external anal sphincter is innervated by the pudendal nerve, which plays a crucial role in motor control and sensation in the anal region.
5. During childbirth, the external anal sphincter may be stretched or torn, potentially leading to complications such as anal incontinence.

Review Questions

• How does the external anal sphincter work in coordination with other structures in the gastrointestinal system?
  • The external anal sphincter works alongside the internal anal sphincter and pelvic floor muscles to control bowel movements. While the internal anal sphincter maintains a resting tone to keep the anal canal closed, the external anal sphincter allows for voluntary control during defecation. When an individual decides to defecate, both sphincters work together; the internal relaxes automatically while the external can contract or relax based on conscious choice.
• What are some potential consequences of injury to the external anal sphincter during childbirth?
  • Injury to the external anal sphincter during childbirth can lead to conditions such as fecal incontinence or impaired bowel control. This may result from tearing or stretching of the muscle during delivery. As a consequence, affected individuals might experience embarrassment and significant changes in lifestyle due to their inability to maintain continence, highlighting the importance of surgical repair if necessary.
• Evaluate how pelvic floor health impacts the function of the external anal sphincter and overall gastrointestinal health.
  • Pelvic floor health is essential for optimal function of the external anal sphincter and overall gastrointestinal health. Weakness or dysfunction in pelvic floor muscles can compromise their ability to support the sphincters effectively, leading to issues such as fecal incontinence or increased pressure on internal structures. Strengthening pelvic floor muscles through exercises like Kegels can improve support for both the internal and external anal sphincters, enhancing continence and reducing gastrointestinal problems.

Related terms

internal anal sphincter:

The internal anal sphincter is an involuntary smooth muscle that maintains constant tension to keep the anal canal closed at rest, contributing to fecal continence.

rectum: The rectum is the final section of the large intestine, connecting the sigmoid colon to the anal canal, where feces are stored before being expelled.

pelvic floor muscles: Pelvic floor muscles support the pelvic organs and help maintain continence by working alongside the anal sphincters during bowel movements.