The document summarizes the structure and organization of typical spinal nerves. It discusses how spinal nerves are formed from the dorsal and ventral roots, containing both sensory and motor fibers. Each spinal nerve exits the vertebral column through an intervertebral foramen, forming 31 pairs of spinal nerves that innervate different regions of the body. The anterior and posterior primary branches of spinal nerves further branch to supply specific regions like the skin and muscles of the back and body wall.

1. Typical Spinal Nerve
Sanjaya Adikari
Department of Anatomy

2. Skull
Vertebral column
• CNS is covered
by the skull and
the vertebral
column
• PNS is outside

3. CNS PNS
Nervous sytem
CNS PNS
Somatic
CNS PNS
autonomic
Nervous sytem

4. Structure of a spinal cord segment
Posterior median septum
Posterior horn
Lateral horn
Anterior horn
Anterior median fissure
Central canal
Posterior white column
Lateral white column
Anterior white column
Anterior nerve root
Posterior nerve root

5. Dorsal root ganglion
Somatic
Autonomic

7. Dorsal and ventral roots
• Dorsal roots contain afferent (sensory) axons
• Ventral roots contain efferent (motor) axons
• The ventral roots continue out from the spinal
cord, and mix with their corresponding dorsal
nerve root at a point after the ganglion
• The combined dorsal and ventral roots are
called a spinal nerve (therefore, spinal nerves
are mixed).

8. Spinal nerve is mixed (motor + sensory + autonomic)

9. Spinal nerve is mixed (motor + sensory + autonomic)
• Spinal nerve refers to the mixed spinal nerve
• It is formed from the dorsal and ventral roots
• Passes out through the intervertebral foramen
• There are 31 bilaterally-paired spinal nerves
– 8 cervical nerves (C1-C8)
– 12 thoracic nerves (T1-T12)
– 5 lumbar nerves (L1-L5)
– 5 sacral nerves (S1-S5)
– 1 coccygeal nerve (Co)

10. 7
12
5
5
8
12
5
5
1
Vertebral column Spinal cord

11. C2
C1
C4
C3
C6
C5
T1
C7
T3
T2
T5
T4
T7
T6
T9
T8
T11
T10
L1
T12
C1
C8
T3
T10
L1, L2
L3, L4
L5
S, C
C1
C7
C8
Spinal nerves
T1
T2
T10

12. Anterior and posterior primary rami
• The posterior primary rami have lateral and medial branches
They supply
– back muscles and skin over the back
• The anterior primary rami give off anterior and lateral
cutaneous branches
They supply
– the rest of the body wall
• Anterior primary rami also give rise to the roots of the
various nervous plexuses

13. Spinal nerves in the thoracic region
Anterior
cutaneous branch
Lateral cutaneous
branch
Medial Lateral
Anterior
Posterior
These are typical spinal
nerves

15. •Gray ramus communicans
unmyelinated
•White ramus communicans
myelinated
Rami communicantes

17. Formed by communicating
branches between anterior
primary rami of spinal nerves.
Anterior primary rami form the
roots of nerve plexus
What are the advantages
of a nerve plexus?
Last’s Anatomy, 10th ed.
Page 13
Nerve plexus

18. Dermatome
Area of skin supplied by a
single spinal nerve or spinal
cord segment
Myotome
The muscle/s supplied by a
single spinal nerve or spinal
cord segment