Answer
The innervation of a muscle is the muscle that stimulates(serves) it. Knowledge of innervation of muscilitates facilitates diagnoses of the injury of specific nerves, spinal cord, or brain stem by the effects on muscle functions which makes possible targeted effective rehabilitation.
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Spinal nerves that innervate muscles leave the spinal cord (SC) through intervertebral foramina. Each the branches to form anterior and posterior ramus. Outside the SC spinal nerves also form weblike plexuses near the vertebral column.
The muscles below the neck are innervated by spinal nerves, For instance , the trapezius is innervated by the accessory nerve; and the anterior rami of C-3-C4, and the serratus anterior is innervated by the long thoracic nerve.
Muscles of the head and neck are served by cranial nerves. For example , facial nerve (CN VII) innervates the muscles of facial expression, and the masseter muscle is innervated by the mandibular nerve , a branch of CN V,(the trigeminal).
Cranial nerves arise from the brain, then emerge through cranial foramina, and innervate muscle of head and neck.
