SPINAL NERVES

• 31 Pairs. Mixed type. Total weight 150 gms.
• At the base of origin of spinal nerves gland of swammardon or calcarious ganglion is present.
• Composed of medulated nerve fibres.
• Classified into five groups -

1. Cervical                          - 8 pairs

2. Thoracic                         - 12 pairs

3. Lumber                           - 5 pairs

4. Sacral                            - 5 pairs

5. Coccygeal                      - 1 pair

• Each spinal nerve is originated from spinal cord from dorsal root and ventral root.
• In dorsal root, root ganglion is present. Both roots fuse in neural canal to form spinal nerve.
• It comes out of vertebral column from inter vertebral foramen.
• Out side vertebral column each spinal nerve is divided into three parts - 

                    (i) Dorsal branch or Ramus dorsalis

                    (ii) Ventral branch or Ramus ventralis

                    (iii) Visceral branch or Ramus communicans

• Dorsal branch to skin and muscle of dorsal side.
• Ventral branch to skin & muslce of ventral side.
• Visceral branch is attached to ganglions of A.N.S.
• In rabbit 37 pairs spinal nerves present -

1. Cervical                          - 8 pairs

2. Thoracic                         - 12 pairs

3. Lumber                           - 7 pairs

4. Sacral                            - 4 pairs

5. Caudal                           - 6 pairs

In rabbit caudal nerves combine with filum terminalis to form cauda equina.