Definition

1. Noun:
   • A ring of muscle that contracts to close an opening: A sphincter muscle is a circular band of muscle fibers that surrounds a natural opening or passage in the body. Its primary function is to constrict or close that opening by contracting.

Usage

• The term "sphincter muscle" is used in anatomical and medical contexts to describe specific muscles that control the flow of substances by opening and closing bodily orifices.
• It is typically modified by the name of the specific orifice it controls (e.g., anal sphincter, pyloric sphincter).

Examples

• Noun:
  • The anal sphincter muscle helps maintain continence.
  • Damage to the esophageal sphincter muscle can cause acid reflux.

Advanced Usage

• Physiological Role: Sphincter muscles are often discussed in terms of their tonic (constant) or phasic (periodic) contraction patterns.
  • The internal anal sphincter provides tonic contraction to maintain closure at rest.

Variants and Related Words

• Sphincter (n): The more common, abbreviated term for "sphincter muscle."
  • The pyloric sphincter regulates the passage of food from the stomach.
• Sphincteric (adj): Relating to or having the characteristics of a sphincter.
  • The patient exhibited impaired sphincteric control.

Synonyms

• Constrictor muscle: A muscle that narrows a passage or compresses an organ.
• Circular muscle: A general term for muscles arranged in a ring-like fashion.

Related Phrases

• Sphincter of Oddi: A specific sphincter muscle controlling the flow of bile and pancreatic juice.
  • Dysfunction of the Sphincter of Oddi can cause severe abdominal pain.
• Sphincterotomy: A surgical procedure to cut a sphincter muscle.
  • The surgeon performed a sphincterotomy to relieve the obstruction.

Noun

1. a ring of muscle that contracts to close an opening