Final answer:
The orbicularis oculi is the circular muscle responsible for blinking and squinting, part of the protective corneal reflex, with control stemming from the corticobulbar tract. It is one of several muscles coordinating eye movements, working alongside the extraocular muscles.
Step-by-step explanation:
The movement of blinking/squinting your eye is initiated by the circular muscle around the eye known as the orbicularis oculi. This muscle is a type of circular muscle, also referred to as a sphincter, which functions to close openings when contracted. The orbicularis oculi is responsible for the closure of the eyelids, a critical action for the protective corneal reflex, which is the eye's response to stimulation such as bright light or foreign objects, promoting eye health and maintaining the moisture of the eye.
Control over this muscle comes from the corticobulbar tract, which is the neural pathway connecting the cerebral cortex to the brain stem, facilitating blinking and other movements of the eye. Various other extraocular muscles coordinate to move the eye in different directions; these muscles, which include the superior and inferior recti and the lateral and medial recti, work in conjunction, allowing the eye to move smoothly and focus on different points in space.