Spinal Nerves

1. Sreenu Thalla
Assistant Professor
Department of Pharmacology

3. Spinal Nerves

4. • 31 pairs of nerves originate on the spinal cord, known as spinal nerves.
• All spinal nerves are mixed nerves, meaning that they carry both sensory
and motor information.
• Spinal nerves are named by the region where they originate and a
number:
 The cervical region has 8 pairs of spinal nerves called C1 - C8
 The thoracic region has 12 pairs of spinal nerves called T1 - T12
 The lumbar region has 5 pairs of spinal nerves called L1 - L5
 The sacral region has 5 pairs of spinal nerves called S1 - S5
 There is one pair of coccygeal nerves called C0

5. • Each spinal nerve originates on the spinal cord as spinal nerve roots,
called ventral and dorsal roots.
• These spinal nerve roots unite close to the spinal cord to form a spinal
nerve.
• Perhaps surprisingly, spinal nerves are very short, only about 1-2
centimeters long before it divides into two branches known as rami.

8. Function of Spinal Cord
• Forms a connecting link between the brain and the PNS
• Provides structural support and builds a body posture
• Facilitates flexible movements
• Myelin present in the white matter acts as an electrical insulation
• Communicates messages from the brain to different parts of the body
• Coordinates reflexes
• Receives sensory information from receptors and approaches towards
the brain for processing.

10. • The brachial plexus is divided into roots, trunks, divisions, cords,
and branches
 roots: ventral roots of spinal nerves C5, C6, C7, C8, and T1
 trunks: superior, middle, and inferior trunks
 divisions: each of the superior, middle, and inferior trunks have an
anterior division and a posterior division (6 divisions total)
Cords
 lateral cord: the anterior divisions from the superior and middle
trunks combine to form the lateral cord
 posterior cord: the posterior divisions from the superior, middle, and
inferior trunks combine to form the posterior cord
 medial cord: comprised of the anterior division of the inferior trunk
Branches - musculocutaneous nerve, axillary nerve, radial nerve, median
nerve, and ulnar nerve

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

15. • 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 that carry sensory messages to
provide motor control to the muscles of the arms and upper back.

17. • T1 and T2 thoracic spinal nerves supply the top of the chest, arms,
and hands.
• T3, T4, and T5 nerves supply into the chest wall as well as aid in
breathing.
• T6, T7, and T8 nerves supply into the chest and down into the
abdomen.
• T9, T10, T11, and T12 nerves supply into the abdomen and lower in the
back.

20. • L1 lumbar spinal nerves provide sensations to the groin as well as the
genitals.
• L2, L3, and L4 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 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.

21. Sacral Nerves
• S1 sacral spinal nerves affect the hips and the groin area.
• S2 nerves affect the back of the thighs.
• S3 nerves affect the medial buttock area.
• S4 and S5 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
Coccygeal Nerves
• CO1 spinal nerves innervate the skin around the coccygeal region,
including around the tailbone.

23. Spinal Nerve Damage
• Pain – from mild to severe
• Changes in sensory sensations
• Weakness of muscles
• Diminished or weakened reflexes
• Feelings of numbness
• Lower back problems
• Tingling sensations in the limbs
Compressive neuropathy
• This condition can occur when the spinal nerves are compressed.
• This can happen when the nerves that exit the spinal cord become
trapped or swollen, and it can be extremely painful.
• This condition typically affects older people, and the effects can be
temporary or long-lasting, permanently destroying the spinal nerves.

24. Herniated disc
• Also known as a slipped disc, this can occur when the vertebrae of the
spine, including the cartilage, ligaments, and muscles, are disrupted.
• This disruption can cause the vertebrae to slip out of place.
• A herniated disc can also cause nerve compression and usually causes
neck pain as a first symptom, accompanied by sensations of tingling,
numbness, and weakness in other parts of the body.
• A Herniated disc can cause permanent damage to the spinal cord.

26. Trauma
• Spinal nerves can become damaged either mildly or severely after
traumatic accidents.
• Trauma to the neck can come as a result of falling or blunt force to the
neck, for instance.
• This trauma can result in swelling, stretching, or tears of the cervical
spinal nerves or the cervical plexus.
• Lifting heavy objects or blunt force to the lower back can result in the
lumbar spinal nerves or lumbar plexus being damaged and lead to
lower back pains.

27. Spinal infections
• Types of spinal infections can include disc infections and spinal bone
infections and typically cause inflammation and pain which may
travel into other parts of the body.
• A spinal infection may begin near spinal nerve roots and thus will
take effect on the spinal nerves which branch from it.

30. Thank You

31. Clinical Application: Epidural (Childbirth)
• An epidural is a medical procedure commonly done to relieve pain
during labor and delivery.
• In this procedure, a needle is inserted into the vertebral canal without
puncturing the dura mater.
• With the tip of the needle/catheter above the dura mater (epi =
above; dural= of the dura mater), anesthetics are injected into the
epidural space.
• The anesthetics then pass through the meninges and block neuronal
impulses, thus inhibiting the transmission of sensation (in this case,
pain) to the brain.

32. • Just like in a lumbar puncture, the epidural needle can be inserted
between L3/L4 vertebrae, but because the pain impulses from the
uterus reach the spinal cord at levels between T10-L1, epidurals are
more commonly placed more superiorly.
• A common location for epidural placement is T7, which is easily
identifiable at about the level of the inferior border of the scapula.
• When the drugs are injected, gravity can pull the drugs downward,
blocking everything below the epidural location.
• Therefore, administering an epidural above the level of T10 can relieve
labor pain from uterine contractions as well as pain from the pelvic
floor transmitted by the pudendal nerve (from S2, S3, and S4 spinal
nerves).

34. Nerve Name Nerves Involved
Cutaneous
Innervation
Muscular Innervation
axillary nerve
ventral rami of C5 and C6 spinal
nerves
skin of the shoulder deltoid and teres minor muscles
dorsal scapular nerve ventral rami of C5 spinal nerve --
levator scapulae, rhomboid major, and
rhomboid minor muscles
long thoracic nerve
ventral rami of C5 through
C7 spinal nerve
-- serratus anterior muscles
median nerve
ventral rami of C5 through
T1 spinal nerves
some skin of the hand
anterior forearm flexor, palm, and digit
muscles
musculocutaneous
nerve
ventral rami of C5 through
C7 spinal nerves
some skin of the forearm
biceps brachii, brachialis, and
coracobrachialis muscles
pectoral nerve
ventral rami of C5 through
T1 spinal nerves
--
pectoralis major and pectoralis minor
muscles
radial nerve
ventral rami of C5 through
T1 spinal nerves
posterolateral skin of the
upper limb
triceps brachii, brachioradialis, and
posterior forearm muscles
subscapular nerve
ventral rami of C5 and C6 spinal
nerves
-- subscapularis and teres major muscles
suprascapular nerve
ventral rami of C5 and C6 spinal
nerves
-- supraspinatus and infraspinatus muscles
ulnar nerve
ventral rami of C8 and T1 spinal
nerves
some skin of the hand
anterior forearm flexor and hand
muscles

35. Nerve Name
Nerves
Involved
Cutaneous
Innervation
Muscular Innervation
common fibular
nerve (superficial
and deep branches)
ventral rami of
L4 through S2 spinal
nerves
skin of the
anterolateral leg and
foot
tibialis anterior, extensor digitorum
longus, fibularis longus and fibularis
brevis muscles
femoral nerve
ventral rami of
L2 through L4 spinal
nerves
skin of the medial
lower limb and
anterior thigh
iliacus, sartorius, pectineus, rectus
femoris, vastus lateralis, vastus medialis,
and vastus intermedius muscles
genitofemoral nerve
ventral rami of
L1 and L2 spinal
nerves
skin of external
genitalia
cremasteric muscles (males only)
iliohypogastric nerve
ventral rami of
L1 spinal nerves
skin of the hip and
inferior abdomen
internal oblique and transversus
abdominis muscles
ilioinguinal nerve
ventral rami of
L1 spinal nerves
skin of the medial
thigh and external
genitalia
internal oblique and Transversus
abdominis muscles
inferior gluteal
nerve
ventral rami of
L5 through S2 spinal
nerves
-- gluteus maximus muscles

36. lateral femoral
cutaneous nerve
ventral rami of L2 and
L3 spinal nerves
skin of the anterolateral
thigh and knee
--
obturator nerve
ventral rami of
L2 through L4 spinal
nerves
skin of thigh (medial)
gracilis, adductor magnus, adductor longus,
and adductor brevis muscles
posterior femoral
cutaneous nerve
ventral rami of
S1 through S3 spinal
nerves
skin of the posterior
lower limb
--
pudendal nerve
ventral rami of
S2 through S4 spinal
nerves
skin of external genitalia
external anal sphincter, external urethral
sphincter, and pelvic muscles
sciatic nerve (branches
into tibial and common
fibular nerves)
ventral rami of
L4 through S3 spinal
nerves
skin of the leg and foot
semitendinosus, semimembranosus, and
biceps femoris muscles
superior gluteal nerve
ventral rami of
L4 through S1 spinal
nerves
--
gluteus medius, gluteus minimus, and tensor
fasciae latae muscles
tibial nerve
ventral rami of
L4 through S3 spinal
nerves
skin of the sole of the
foot and posterior leg
flexor digitorum longus, gastrocnemius, and
soleus muscles