Iris sphincter muscle Iris sphincter muscle The iris sphincter muscle (pupillary sphincter, pupillary constrictor, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris. It encircles the pupil of the iris, appropriate to its function as a constrictor of the pupil. It is found in vertebrates and some cephalopods. Initially, all the myocytes are of the smooth muscle type but, later in life, most cells are of the striated muscle type. Its dimensions are about 0.75 mm wide by 0.15 mm thick. In humans, it functions to constrict the pupil in bright light (pupillary light
Muscle Beach the original Santa Monica site. The contemporary Muscle Beach Venice is located two blocks north of Venice Boulevard on Ocean Front Walk in Venice, California. Santa Monica's "Muscle Beach" landmark derives its name from the growing local and national reputation of gymnastics and strength athletes who congregated at what was first known simply as the "Santa Monica Beach Playground", with the 'muscle' term gaining momentum by 1940. The 1940 opening of the first of an eventual nationwide chain of weightlifting gyms by famed pioneer gym chain operator, Vic Tanny, only two city blocks from Muscle Beach in Santa Monica, is