Question

Explain the formation of a typical spinal nerve with the help of a neat labelled diagram.

Answer 1

                Formation of Spinal Nerve

1. All spinal nerves are of the mixed type i.e. they have some nerve fibre as sensory and some motor.
2.  Each spinal nerve is formed inside the neural canal of vertebral column by two roots - the posterior or dorsal sensory root and anterior or ventral root.
3.  Anterior root receives the sensory nerve from the dorsal root ganglion (cell bodies of sensory neurons are located in the ganglion), while the anterior/ventral root gives out the motor nerve.
4. The dorsal sensory and the ventral motor nerves together form the mixed spinal nerve.
5. It emerges out from both sides of the spinal cord through the intervertebral foramen.
6. As soon as it emerges out of vertebral column, it shows three branches viz.

1. Ramus dorsalis: From skin and to muscles of dorsal side.
2. Ramus ventralis: The largest of the three supplies the organs and muscles on lateral and anterior side.
3. Ramus communicans: The smallest of the three and given out from 1st thoracic upto 3rd lumbar (L3) spinal nerve. It joins the sympathetic ganglia.