The superior oblique muscle ends in a tendon that passes through a fibrous loop, the trochlea, located anteriorly on the medial aspect of the orbit. Trochlea means “pulley” in Latin; the fourth nerve is named after this structure.

Why is trochlear nerve called trochlear?

As the fibres from the trochlear nucleus cross in the midbrain before they exit, the trochlear neurones innervate the contralateral superior oblique. The tendon of the superior oblique is tethered by a fibrous structure known as the trochlea, giving the nerve its name.

What is the origin of the trigeminal nerve?

The origin of the trigeminal nerve is the annular protuberance at the limit of the cerebellar peduncles. It originates from three sensory nuclei (mesencephalic, principal sensory, spinal nuclei of trigeminal nerve) and one motor nucleus (motor nucleus of the trigeminal nerve) extending from the midbrain to the medulla.