typical spinal nerve sanjaya adikari department of anatomy
TRANSCRIPT
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Typical Spinal Nerve
Sanjaya AdikariDepartment of Anatomy
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Skull
Vertebral column
• CNS is covered
by the skull and
the vertebral
column
• PNS is outside
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C N S P N S
N ervous sytem
C N S P N S
S o m a tic
C N S P N S
a u to n om ic
N e rvo us sytem
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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
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Dorsal root ganglion
Somatic
Autonomic
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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).
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Spinal nerve is mixed (motor + sensory + autonomic)
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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)
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7
12
5
5
8
12
5
5
1
Vertebral column Spinal cord
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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
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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
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Spinal nerves in the thoracic region
Anterior cutaneous branch
Lateral cutaneous branch
Medial Lateral
Anterior
Posterior
These are typical spinal nerves
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• Gray ramus communicans
unmyelinated
• White ramus communicans
myelinated
Rami communicantes
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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
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DermatomeArea 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