The nerves arising from the spinal cord are called spinal nerves. There are 37 pairs of spinal nerves in Rabbit. Each spinal nerve arises from the spinal cord by two roots, a dorsal or sensory root and a ventral or motor root. These roots unite to form a nerve. The dorsal root contains a small dorsal ganglion just outside the neural canal. After originating from the spinal cord thus formed passes out of neural canal through intervertebral foramen.
Each spinal nerve divides into 3 branches. These are:
a. Ramus dorsalis (dorsal branch): It divides into several branches which enter the skin and muscles of dorsal body wall. It contains somatic sensory fibres.
b. Ramus ventrails (ventral branch): It is a long main branch. It supplies nerves to the muscles of belly (Ventral body wall). It contains somatic motor fibres. The prominent ventral branch is generally considered as the spinal nerve.
c. Ramus communicans (visceral branch): It joins with sympathetic ganglion. It contains both visceral sensory and visceral motor fibres.
The brachial phlexus is formed by the ventral branches of 4th to 9th spinal nerves. The lumbar phlexus is formed by the ventral branches of 24th to 27th spinal nerves. Sacral phlexus is formed by the ventral branches of 28th to 31st spinal nerves.
The posterior spinal nerves run backward in the neural canal before they comeout as a bunch. This bunch along with filum terminal resembles to the tail of horse, hence called cauda equina.