noun
sphincter muscle of the pupil; sphincter pupillae
Anatomical term for the circular muscle that constricts the pupil.
瞳孔括約筋は、明るい光に反応して収縮する。
The sphincter muscle of the pupil contracts in response to bright light.
The dilator muscle of the pupil, which works antagonistically to the sphincter pupillae.
Compound of 瞳孔 (pupil) + 括約筋 (sphincter muscle).