The Iris - this is a muscularly operated diaphragm which controls the amount of light entering the eye.
(this; is; a muscularly operated diaphragm which controls the amount of light) (a muscularly operated diaphragm; controls; the amount of light) (light; entering; the eye)
this a muscularly operated diaphragm light
is controls entering
a muscularly operated diaphragm which controls the amount of light
the amount of light
the eye