In a patient with a history of depression, anxiety, and fatigue, who has undergone surgery, which sphincter muscle, internal (involuntary) or external (voluntary), controls the passage of gas and stool last?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: January 22, 2026 • View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

Anal Sphincter Anatomy: Order of Passage

Gas and stool pass through the external anal sphincter (EAS) last, after passing through the internal anal sphincter (IAS). The external sphincter is the final barrier under voluntary control before defecation occurs.

Anatomical Sequence of Defecation

The passage of stool and gas follows this anatomical pathway:

  • The internal anal sphincter (IAS) is encountered first - this is a smooth muscle structure under involuntary autonomic control that maintains resting anal tone 1

  • The external anal sphincter (EAS) is the final barrier - this striated muscle is under voluntary control and represents the last sphincter that must relax for defecation to occur 1

  • Voluntary control occurs at the external sphincter level - the EAS can be consciously contracted or relaxed, allowing individuals to defer defecation until socially appropriate 1

Clinical Relevance for Post-Surgical Patients

Sphincter Function and Control

  • The external sphincter responds to voluntary muscle training through pelvic floor exercises, as it is composed of striated muscle under conscious control 1

  • The internal sphincter cannot be strengthened through voluntary exercise training because it consists of smooth muscle under autonomic control 1

Implications for Patients with Depression and Anxiety

  • Depression and anxiety are common after abdominal surgery, occurring in 6-16% of patients within 1-5 years post-surgery, and may affect bowel function perception 2

  • Psychological factors can influence surgical outcomes and symptom reporting, particularly regarding bowel control and quality of life 3, 4

  • Younger patients and women are at higher risk for psychological sequelae after colorectal surgery, with 28% of post-surgical patients screening positive for at least one psychological condition 3

Post-Surgical Considerations

  • Fatigue is a common post-surgical complaint that may affect the ability to maintain voluntary external sphincter control, particularly in patients with depression 2

  • Cognitive behavioral therapy should be considered as it improves both psychological outcomes and physical functioning in surgical patients with depression and anxiety 1

References

1
Guideline

Pelvic Floor Therapy and Sphincter Muscle Strengthening

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

2
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

3
Research

Psychological sequelae of colonic resections.

Colorectal disease : the official journal of the Association of Coloproctology of Great Britain and Ireland, 2020

Related Questions

What is the recommended localized treatment approach for a patient with local recurrence of conjunctival melanoma after surgical excision?
What does moderate sludge on a gallbladder ultrasound indicate in a patient, particularly in females or those with a history of rapid weight loss or prolonged fasting?
How to manage hyperkalemia in a patient on Lovenox (enoxaparin)?
Which sphincter muscle is most related to outer rectum control in a patient with a history of depression, anxiety, and fatigue, who has undergone surgery?
Can a patient with a history of depression, anxiety, and fatigue, who has undergone surgery, voluntarily contract their internal anal sphincter muscle in the same way as their external anal sphincter muscle during bowel movements?
In a patient with a history of depression, anxiety, and fatigue, does the sensation of fullness during bowel movements originate from the internal or external anal sphincter muscle?

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.

Ask Question