GROSS ANATOMY

Detailed explanation-1: -Trapezius and sternocleidomastoid muscles have branchiomeric origin; the afferents that derive from these muscles reach the nucleus of the solitary tract. The trapezius muscle elevates, lowers, adduces and abducts, and externally rotates the scapula. It extends the head by rotating it to the opposite side.

Detailed explanation-2: -This nerve supplies the sternocleidomastoid and trapezius muscles, which have the following functions: Rotation of head away from the side of the contracting sternocleidomastoid muscle. Tilting of the head toward the contracting sternocleidomastoid muscle. Flexion of the neck by both sternocleidomastoid muscles.

Detailed explanation-3: -The spinal accessory nerve originates from neuronal cell bodies located in the cervical spinal cord and caudal medulla. Most are located in the spinal cord and ascend through the foramen magnum and exit the cranium through the jugular foramen.

Detailed explanation-4: -Clinical relevance: assessing the accessory nerve Examination of the accessory nerve involves assessing two muscles: the trapezius and sternocleidomastoid.

Detailed explanation-5: -Different from the other cranial nerves, each accessory nerve has some motor fibers originating in the lateral area of the anterior gray horns of the first five cervical spinal cord segments. The somatic motor fibers form the spinal root of CN XI, entering the cranium via the foramen magnum.