Definition

1. Noun:
   • A ring of smooth muscle surrounding the iris: The musculus sphincter pupillae is a specific anatomical structure. It is a circular band of smooth muscle fibers located at the margin of the pupil within the iris of the eye.

Usage

• The term is used exclusively in technical, medical, and anatomical contexts to refer to this precise structure. It is not used in everyday conversation.
• It functions to constrict the pupil in response to bright light or during accommodation for near vision.

Examples

• Noun:
  • Damage to the musculus sphincter pupillae can result in a permanently dilated pupil.
  • The musculus sphincter pupillae is innervated by parasympathetic fibers from the oculomotor nerve.

Advanced Usage

• Clinical Context: Often discussed in relation to pupillary light reflexes, neurological examinations, and certain eye diseases or injuries.
  • The physician tested the function of the musculus sphincter pupillae by shining a light into the patient's eye.

Variants and Related Words

• Pupillary sphincter: A more common clinical synonym for .
• Iris sphincter muscle: Another equivalent term.
• Sphincter pupillae: A shortened, yet still technical, form.
• Antagonist muscle: The (pupillary dilator) is the opposing muscle that enlarges the pupil.

Synonyms

• Pupillary sphincter
• Iris sphincter muscle

Notes

• This is a Latin-derived anatomical term. In many medical texts, Latin names are standard for describing muscles and other structures.
• There are no idioms, phrasal verbs, or colloquial uses associated with this highly specialized term.

Noun

1. a ring of smooth muscle surrounding the iris