THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -Origin and course The trochlear nerve (CN IV) arises from the trochlear nucleus located within the periaqueductal gray substance of the midbrain and emerges on the dorsal midbrain caudal to the inferior colliculus. It then crosses the midline, before passing anteriorly around the contralateral side of the brainstem.

Detailed explanation-2: -The trochlear nerve (/ˈtrɒklɪər/), (lit. pulley-like nerve) also known as the fourth cranial nerve, cranial nerve IV, or CN IV, is a cranial nerve that innervates a single muscle-the superior oblique muscle of the eye (which operates through the pulley-like trochlea).