spinal cord and spinal nerves sanjaya adikari department of anatomy
TRANSCRIPT
Spinal cord and
spinal nerves
Sanjaya AdikariDepartment of Anatomy
Spinal cordExtends from the foreman
magnum to the lower
border of L1
Divided into five regions
Covered by the meninges
for protection
CSF in the subarachnoid
space
Coverings of the spinal cord
Spinal nerves
Spinal nerves come out through the intervertebral foramina
7
12
5
5
8
12
5
5
1
Vertebral column Spinal cord
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
Cauda equina
Consists of sensory and motor nerve roots below L1
These are unmixed/pure nerves
Pia mater continues below L1 as a cord named filum terminale
T12
L1
L2
L3
L4
L5
Sacrum
Coccyx
Foetus at 3 months
T12
L1
L2
L3
L4
L5
Sacrum
Coccyx
Adult
Length of the spinal cord
T12
L1
L2
L3
L4
L5
Sacrum
Coccyx
At birth
S2
Black line indicates dura and arachnoid together. Pia is in blue.
Lumbar puncture
Performed to get CSF for investigation
Vertebral column is fully flexed
Needle inserted between L3 and L4 spines (or one space above)
Collects CSF from subarachnoid space
What are the risks of lumbar puncture ?
Cross section of spinal cord 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
Dorsal root ganglion
Somatic
Autonomicsensory
motor
Dorsal root ganglion
Somatic
Autonomicsensory
motor
Dorsal and ventral roots
• Posterior roots contain afferent (sensory) axon
• Anterior roots contain efferent (motor) axons
• The anterior roots continue out from the spinal
cord, and mix with their corresponding posterior
nerve root at a point after the ganglion
• Combination of the two roots is called a mixed
spinal nerve.
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)
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
Nerve plexus
Is formed by nerves interlaced with numerous communicating branches
What are the advantages of a nerve plexus?
Last’s Anatomy, 10th ed. Page 13
Blood supply of spinal cord
• Two posterior spinal arteries– Arise from PICA– Supply posterior 1/3 of spinal cord
• One anterior spinal artery– Arise as two from vertebral arteries– Supply anterior 2/3 of spinal cord
• Segmental spinal arteries– Enter the vertebral canal through intervertebral
foramina– Divides into anterior & posterior radicular
arteries. Radicular arteries accompany nerve roots
• Ant/post spinal arteries become very
small at thoracic region and the
segmental spinal arteries and
additional feeder arteries compensate
for the deficiency
• Venous drainage is into internal vertebral venous plexus