Spinal nerves M. Thiru murugan Spinal nerves The spinal nerves are the major nerves of the body within the peripheral nervous system (PNS). These nerves are an integral part of the PNS in that they control motor, sensory, and autonomic functions between the spinal cord and the body. There are 31 pairs of spinal nerves, located at the cervical, thoracic, lumbar, sacral, and coccygeal levels 8 pairs of cervical nerves (C1 to C8). 12 pairs of thoracic nerves (T1 to T12). 5 pairs of lumbar nerves (L1 to L5). 5 pairs of sacral nerves (S1to S5). 1 pair of coccygeal nerves (CO1). Each of these nerves branch out from the spinal cord, dividing and subdividing to form a network connecting the spinal cord to every part of the body. Spinal nerves are structures which receives sensory information from receptors of the periphery body, and then transmits this information to the CNS. Similarly, the spinal nerves transmit motor commands from the CNS to the muscles and glands of the periphery, so the brain’s instructions can be carried out quickly. Anatomy of Spinal Nerves Spinal nerves are relatively large nerves which are distributed evenly along the spinal cord and the spine. These spinal nerves are large as they are formed by both sensory and motor nerve roots merging together. These nerve roots emerge from the spinal cord, the sensory roots from the back of the spinal cord, whereas the motor roots emerge from the front. Each nerve root comprises of approximately 8 nerve rootlets and as they join together, they form the spinal nerves which project off the spinal cord. The spinal nerves are formed within a few centimeters of the spine on each side. Some groups of nerves merge to form a large plexus of nerves, whereas some divide into smaller branches without forming a plexus. Spinal nerves emerge from the spinal column through an opening between nearby vertebrae (known as Intervertebral foramen). This is the case for all of the spinal nerves except the first pair, which emerge between the occipital bone and the uppermost vertebrae. Types and Functions of Spinal Nerves: As spinal nerves contain both sensory and motor fibres, so have both sensory and motor functions. For sensory functions, the spinal nerves receive sensory messages from the skin, internal organs, and the bones. These spinal nerves will then send this sensory information to the sensory roots before reaching the sensory fibres at the back of the spinal cord. For motor functions, the motor roots receive nerve messages via the front of the spinal cord and then transmits these messages to the spinal nerves. Information will be sent to small nerve branches which will activate the muscles of the limbs and other body parts. Cervical Nerves: There are 8 cervical nerves on each side of the spine (C1 to C8), located at the top of the spine, of the cervical vertebrae. The cervical nerves C1 to C5 can form a cervical plexus through the merging of these nerves. These can divide into smaller nerves

1. Spinal nerves

2. Spinal nerves
• The spinal nerves are the major nerves of the body within the peripheral
nervous system (PNS).
• These nerves are an integral part of the PNS in that they control motor,
sensory, and autonomic functions between the spinal cord and the body.
• There are 31 pairs of spinal nerves, located at the cervical, thoracic,
lumbar, sacral, and coccygeal levels
8 pairs of cervical nerves (C1 to C8).
12 pairs of thoracic nerves (T1 to T12).
5 pairs of lumbar nerves (L1 to L5).
5 pairs of sacral nerves (S1to S5).
1 pair of coccygeal nerves (CO1).

3. • Each of these nerves branch out from the spinal cord,
dividing and subdividing to form a network connecting the
spinal cord to every part of the body.
• Spinal nerves are structures which receives sensory
information from receptors of the periphery body, and then
transmits this information to the CNS.
• Similarly, the spinal nerves transmit motor commands from
the CNS to the muscles and glands of the periphery, so the
brain’s instructions can be carried out quickly.

5. Anatomy of Spinal Nerves
• Spinal nerves are relatively large nerves which are distributed
evenly along the spinal cord and the spine.
• These spinal nerves are large as they are formed by both sensory
and motor nerve roots merging together.
• These nerve roots emerge from the spinal cord, the sensory roots
from the back of the spinal cord, whereas the motor roots emerge
from the front.
• Each nerve root comprises of approximately 8 nerve rootlets and
as they join together, they form the spinal nerves which project off
the spinal cord.

6. •The spinal nerves are formed within a few centimeters of the
spine on each side.
• Some groups of nerves merge to form a large plexus of
nerves, whereas some divide into smaller branches without
forming a plexus.
•Spinal nerves emerge from the spinal column through an
opening between nearby vertebrae (known as Intervertebral
foramen).
•This is the case for all of the spinal nerves except the first pair,
which emerge between the occipital bone and the uppermost
vertebrae.

7. Types and Functions of Spinal Nerves:
• As spinal nerves contain both sensory and motor fibres, so have both
sensory and motor functions.
• For sensory functions, the spinal nerves receive sensory messages from
the skin, internal organs, and the bones.
• These spinal nerves will then send this sensory information to the sensory
roots before reaching the sensory fibres at the back of the spinal cord.
• For motor functions, the motor roots receive nerve messages via the
front of the spinal cord and then transmits these messages to the spinal
nerves.
• Information will be sent to small nerve branches which will activate the
muscles of the limbs and other body parts.

8. Cervical Nerves:
• There are 8 cervical nerves on each side of the spine (C1 to C8),
located at the top of the spine, of the cervical vertebrae.
• The cervical nerves C1 to C5 can form a cervical plexus through
the merging of these nerves. These can divide into smaller nerves
which can carry sensory messages and provide motor control to the
muscles of the neck and shoulders.
• Likewise, a brachial plexus can be formed by the combining of
the nerves from C5 to thoracic nerve T1.
• This plexus can branch into nerves which carry sensory messages
to provide motor control to the muscles of the arms and upper
back

9. Cervical Nerves

10. C1, C2, and C3: these cervical spinal nerves help to control the head
and neck, including forward, backward, and sideward movements.
C4: these help to control the upper shoulder movements, as well as
helping to power the diaphragm.
C5: these help to control the deltoids and biceps, the areas of the
upper arm, down to the elbows.
C6: these help to control the wrist extensions, with some supply given
to the biceps.
C7: these help to control the triceps as well as the wrist extensor
muscles.
C8: these help to control the hands, as well as finger flexion (hand
grip).

11. Thoracic Nerves:
• Next, below the cervical nerves, are 12 pairs of thoracic nerves on
each side of the spine (T1 to T12), located at the thoracic vertebrae of
the spine.
T1 and T2: these thoracic spinal nerves supply the top of the chest,
arms, and hands.
T3, T4, T5: these nerves supply into the chest wall as well as aid in
breathing.
T6, T7, T8: these nerves supply into the chest and down into the
abdomen.
T9, T10, T11, T12: these nerves supply into the abdomen and lower in
the back.

13. Lumbar Nerves
• Below the thoracic nerves are 5 pairs of lumbar nerves on each side of the
spine (L1 to L5), located at the lumbar vertebrae of the spine.
L1: these lumbar spinal nerves provide sensations to the groin as well as the
genitals.
L2, L3 and L4: these nerves provide sensations to the front of the thighs and
the inner side of the lower legs. They also help to control movements of the hip
and knee muscles.
L5: these nerves provide sensations to the outer side of the lower legs and the
upper foot. These also help to control the hips, knees, feet, and toe movements.
• The lumbar nerves L1 to L4 can combine to form the lumbar plexus, dividing
into nerves that carry sensory messages and provide motor control to the
muscles of the abdomen and legs.

15. Sacral Nerves
• Further down the spine are 5 pairs of sacral nerves on each side of
the spine (S1 to S5), located at the sacrum.
S1: these sacral spinal nerves affect the hips and the groin area.
S2: these nerves affect the back of the thighs.
S3: these nerves affect the medial buttock area.
S4 and S5: these nerves affect the perineal area.
• The spinal nerves from lumbar L4 to sacral nerves S4 can form the
sacral plexus through the merging of these nerves. This plexus can
divide into nerves that carry sensory messages and provide motor
control to the muscles of the legs.

17. Coccygeal Nerves:
• Finally, at the base of the spine are 1 pair of coccygeal nerves on each side of the
spine (CO1), located at the coccyx.
CO1: these spinal nerves innervate the skin around the coccygeal region,
including around the tailbone.

18. • The conus medullaris (medullary cone) is the cone-shaped end part of
the spinal cord.
• The tip of the conus medullaris is found between the L1 and L2 vertebra.
• The conus medullaris is tethered to the coccyx by a fibrous cord called
the filum terminale, which stabilizes the distal end of the spinal cord.
• Distal to the conus medullaris is a collection of spinal nerve roots called
the cauda equina, that emerges from the lumbosacral part of the spinal
cord below the L1 vertebra & descends toward the coccyx.
• The cauda equina is translated from Latin into ‘horse’s tail’, & was so
named due to its resemblance to the tail of a horse.
• The conus medullaris & cauda equina give rise to spinal nerves that
provide all motor & sensory Innervation to the lower limbs, pelvis and
perineum as well as parasympathetic Innervation to the pelvic viscera.