dilator

Dilator is a term used in medicine and anatomy to denote something that causes dilation: an instrument, a substance, or a muscle that enlarges a passage or opening.

Medical dilators are slender tools inserted into body orifices, used to gradually widen tunnels or cavities. They come in graduated sizes and may be single-use or reusable. Common examples include vaginal dilators used to manage or prevent vaginal stenosis; urethral dilators (bougies) used to treat urethral strictures; and anal dilators used in proctology or sexual therapy. They may be manual or inflated with a balloon, and use lubrication to minimize trauma. Medical practice requires supervision to minimize injury and infection.

Anatomical use: a dilator muscle enlarges a body part. The iris dilator (dilator pupillae) is a smooth muscle under sympathetic control that enlarges the pupil; its antagonist, the sphincter pupillae, constricts the pupil. Other dilator muscles exist in various organs and glands to widen ducts or lumina, usually by contraction.

Pharmacology: vasodilators are drugs that cause widening of blood vessels, reducing vascular resistance and increasing blood flow. They are used to treat hypertension, angina, heart failure, and some forms of shock, and include nitrates, calcium channel blockers, hydralazine, and ACE inhibitors or ARBs as part of broader blood pressure regimens.

Etymology and usage notes: "dilator" derives from Latin dilatare, "to widen"; related terms include dilatation, dilation, and dilator muscle.