GROSS ANATOMY

Detailed explanation-1: -Accessory nerve. The accessory nerve provides motor function to some muscles in the neck. It controls the sternocleidomastoid and trapezius muscles that allow a person to rotate, extend, and flex the neck and shoulders. The accessory nerve separates into spinal and cranial parts.

Detailed explanation-2: -The spinal component of the accessory nerve provides motor control of the sternocleidomastoid and trapezius muscles. The trapezius muscle controls the action of shrugging the shoulders, and the sternocleidomastoid the action of turning the head.

Detailed explanation-3: -The ipsilateral activation of the XI nerve can activate the intrinsic laryngeal muscles fibers for the correct movement of the vocal cords of the same side. The main functions remain those of contracting the trapezius muscle and the sternocleidomastoid.

Detailed explanation-4: -The accessory nerve (Fig. 1), named after Thomas Willis (Willis, 1965) cranial nerve XI, innervates the sternocleidomastoid (SCM) and trapezius muscles.

Detailed explanation-5: -Innervation. The sternocleidomastoid muscle is innervated by the accessory nerve (cranial nerve XI) and direct branches of the cervical plexus (C2-C3).