Nervous system - spinal nerves, Biology


  • 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.

Posted Date: 10/3/2012 1:56:47 AM | Location : United States

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