What is the primary function of cranial nerve III?

The primary function of cranial nerve III, also known as the oculomotor nerve, is to control eye movement and pupillary response to light. This nerve is responsible for the majority of eye movements, innervating several extraocular muscles that allow the eyes to move up, down, and medially. In addition to muscle control, cranial nerve III also plays a crucial role in autonomic functions, such as controlling the size of the pupil in response to light (pupillary light reflex) and enabling the lens to focus on near objects (accommodation). This dual role highlights its importance in both voluntary and involuntary eye functions, making it essential for proper visual orientation and response to surrounding light conditions.