The Sphincters of the Eyes

The iris is composed of two types of muscle. The dilator muscles, and these are long muscle fibres that cause the people to expand when they contract. And then the second type within the iris is the sphincter muscle. This is a ring of muscle tissue around the inner edge of the iris that shrinks the pupil when it contracts. It actually just means any ring of muscle that works to open and close a tube in an animal body. So you actually have multiple sphincters throughout your body, not just in the anus, but also internally, controlling the openings of the stomach. But this will actually play into what i am about to talk about,