The term "sphincter oculi" refers to the circular muscle that surrounds the eye's pupil, controlling the size of the aperture. The IPA phonetic transcription for this word is /ˈsfɪŋktər ˈɒkjʊlaɪ/. The term is spelled phonetically based on the Latin roots of the word. "Sphincter" comes from the Greek word "sphingter," meaning "a tight binder," while "oculi" is the genitive form of the Latin word for "eye." The combined term is commonly used in medical and anatomical studies.
The term "sphincter oculi" refers to a small circular muscle located around the eye. The sphincter oculi muscle is responsible for controlling the size of the pupil, the dark circular opening in the center of the iris, which allows light to enter the eye.
The sphincter oculi muscle is part of the iris, the colored portion of the eye. Its primary function is to regulate the amount of light that enters the eye by constricting or dilating the pupil. When the sphincter oculi contracts, it causes the pupil to constrict or become smaller, which reduces the amount of light entering the eye. Conversely, when the muscle relaxes, the pupil dilates or becomes larger, allowing more light to enter the eye.
The contraction and relaxation of the sphincter oculi muscle are controlled by the autonomic nervous system, specifically the parasympathetic branch. This muscle plays a crucial role in maintaining optimal visual acuity in varying lighting conditions.
Disorders or abnormalities in the sphincter oculi muscle can lead to changes in pupil size, affecting vision. Such conditions include Horner's syndrome, wherein the pupil remains constricted due to damage to the sympathetic nervous system, and Adie's syndrome, characterized by an abnormally dilated pupil on one side.
Musculus orbicularis oculi.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.
The word "sphincter oculi" is derived from two Latin roots: "sphincter" and "oculi".
1. "Sphincter": The term "sphincter" comes from the Greek word "sphingktḗr", which means "a band that binds tight". It refers to a circular muscle that surrounds and contracts an opening in the body, thus controlling the flow of fluids or substances through that opening. The Latin adaptation of this term is "sphincter", which retained its meaning.
2. "Oculi": The term "oculi" is derived from the Latin word "oculus", which means "eye". It refers to the external part of the eye, including its muscles, lids, and surrounding structures.
When combined, "sphincter oculi" translates to "sphincter of the eye".