Download The Spinal Nerves

The Spinal Nerves
SHANDONG UNIVERSITY
Liu Zhiyu
General description
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31 pairs spinal nerves:
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Cervical nerves—8 pairs (C1-C8)
Thoracic nerves—12 pairs (T1-T12)
Lumbar nerves—5 pairs (L1-L5)
Sacral nerves—5 pairs (S1-S5)
Coccygeal nerves—1 pair (Co1)
General Description
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Formation: each spinal nerve is
formed by union of anterior and
posterior roots at intervertebral
foramen
 The anterior root－contains
motor fibers for skeletal muscles.
Those from T1 to L2 contain
sympathetic fibers; S2 to S4 also
contain parasympathetic fibers.
 The posterior root－contains
sensory fibers whose cell bodies
are in the spinal ganglion.
Functional Components of Spinal Nerves
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Somatic efferent nerve fibers (SE): fibers that transmit motor impulses
from spinal cord to skeletal muscles.
Visceral efferent nerve fibers (VE): fibers that transmit motor impulses
from spinal cord to smooth muscles, cardiac muscle and glands.
Somatic afferent nerve fibers (SA): fibers that transmit exteroceptive and
proprioceptive impulses from body to spinal cord
Visceral afferent nerve fibers (VA): fibers that transmit interoceptive
impulses from the viscera to spinal cord
Branches of spinal nerves
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Anterior branch
Posterior branch
Communicating branch
Meningeal branch
Cervical plexus
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Formation: formed by
anterior rami of C1-C4
spinal nerves
Position: lies in front of the
origin of levator scapulae
and scalenus medius and
deep to the superior part of
the sternocleidomastoid
C1
C2
C3
C4
Branches of Cervical Plexus
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Cutaneous branches:
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Lesser occipital
Great auricular
Transverse nerve of neck
Supraclavicular nerves
Emerge around middle of
posterior border of
sternocleidomastoid, to
supply skin of neck and scalp
between auricle and external
occipital protuberance
Branches of Cervical Plexus
Phrenic nerve
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Arises from anterior rami of C3-C5
(motor and sensory)
Runs vertically downward across the
front of the scalenus anterior
Enters the thorax by passing betweem
the subclavian a. and v.
Branches of Cervical Plexus
Phrenic nerve
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Accompanied by pericardiophrenic
vessels and passes anterior to lung
roots between mediastinal pleura and
pericardium to supply motor and
sensory innervation to diaphragm
Sensory fibers supply to pleurae,
pericardium and peritoneum of
diaphragm; usually right phrenic nerve
may be distributed on live, gallbladder
and biliary system.
Brachial Plexus
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Formation:
Formed by anterior rami of C5C8 and T1 spinal nerves
Position:
Passes through the scalene
fissure to posterosuperior of
subclavian artery, then enters
the axilla to form three cords
Main branche of brachial plexus
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Lateral cord
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Medial cord
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musculocutaneous n.
lateral root of median n.
medial root of median n.
ulnar n.
Posterior cord
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radial n.
axillary n.
Main Branche of Brachial Plexus
Musculocutaneous nerve
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Origin: arises from the lateral cord of the
brachial plexus.
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Distribution:
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Biceps brachii
Brachalis
BBC nerve
Coracobrachialis
Skin on anterior aspect of forearm
Main Branche of Brachial Plexus
Median nerve
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Origin: arises from the medial and lateral
cord of the brachial plexus.
Muscular branches:
 Flexor of forearm except
brachioradialis flexor carpi ulnaris and
ulnar half of flexor digitorum profundus
 Thenar except adductor pollicis, first
two lumbricals
Cutaneous branches：
 Skin of thenar, central part of palm,
 Palmar aspect of radial three and onehalf fingers, including middle and distal
fingers on dorsum
Injury: Apehand
Main Branche of Brachial Plexus
Ulnar nerve
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Origin: arises from the medial cord of
the brachial plexus.
Muscular branches:
Flexor carpi ulnaris, ulnar half of flexor
digitorum profundus, hypothenar
muscles, interossei, 3rd and 4th
lumbricals and adductor pollicis;
Cutaneous branches：
Skin of hypothenar, palmar surface of
ulnar one and one-half fingers, ulnar
half of dorsum of hand, posterior
aspect of ulnar two and one-half
fingers
Injury: clawhand
Radial nerve
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Origin: arise from the posterior
cord of the brachial plexus
Course: Winds around the back of
the arm in the spinal groove of the
back of the humerus between the
heads of the triceps. It pierces the
lateral fascial septum above the
elbow and divides into superficial
and deep branches.
Radial nerve
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Distribution:
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Extensor muscles of arm and
forearm, brachioradialis;
skin on back of arm, forearm,
and radial side of dorsum of
hand and radial two and onehalf fingers
Injury: wristdrop
Main Branche of Brachial Plexus
Axillary
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Origin: arises from the posterior
cord of the brachial plexus.
Distribution: Deltoid and teres
minor muscle; skin over deltoid
and upper posterior aspect of
arm
Injury: result in deltoid andteres
minor paralysis (loss of shoulser
abdution and weel external
rotation) with loss of sensation
over the deltoid
Anterior branches of thoracic nerves
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Intercostal nerves (anterior
rami of T1- T11)
Subcostal nerve (anterior
ramus of T12)
Distribution: distributed to
intercostales and
anterolateral abdominal
muscles, skin of thoracic and
abdominal wall, parietal
pleura and peritoneum
Segmental Innervation of Skin
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Adjacent dermatomes
overlap considerably,
so that to produce a
region of complete
anesthesia at least
three contiguous spinal
nerves have to be
sectioned.
Segmental Innervation of Skin
Dermatome: the area of skin supplied by a
single nerve, and, therefore, a single
segment of the spinal cord. On the trunk
the dermatomes extend round the body
from the posterior to the anterior median
plane.
 T2
Sternal angle
 T4
Nipple
 T6
Xiphoid process
 T8
Costal arch
 T10 Umbilicus
 T12 Midpoint between umbilicus and
symphysis pubis
Lumbar plexus
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Formation: formed by anterior
rami of L1-L3, a part of anterior
rami of T12and L4
L1
L2
L3
L4
Main branche of lumbar plexus
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Position: lies within
substance of psoas major
Branches
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Iliohypogastric
Ilioinguinal
Lateral femoral cutaneous
Femoral
Obturator
Genitofemoral
Branches of Lumbar Plexus
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Femoral nerve
passes deep to inguinal ligament;
supplies anterior thigh muscles
(quadriceps, sartorius and pectineus),
hip and knee joint, and skin on
anteromedial side of thigh, saphenous
nerve is distributed to skin of medial side
of leg and foot
Obturator nerve
Enters thigh through obturator foramen;
supplies medial group of muscles of
thigh, obturator externus, and skin of
medial side of thigh
Sacral Plexus
L4
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Formation: formed by
anterior rami of L4 and
L5 spinal nerves (the
lumbrosacral trunk) and
anterior rami of sacral
and coccygeal nerves
Position: lies in pelvic
cavity, anterior to sacrum
and piriformis
L5
S1
S2
S3
S4
S5
Co
Main branches of sacral plexus
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Superior gluteal n.
Inferior gluteal n.
Pudendal n.
Posterior femoral cutaneou n.
Sciatic n.
Branches of Sacral Plexus
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Sciatic nerve
Leaves pelvis through infrapiriform
foramen to enter gluteal region, runs
inferiorly laterally deep to gluteus
maximus, passing midway between the
greater trochanter of femur and ischial
tuberosity to back of thigh, lying deep to
long head of biceps femoris, normally
divided into tibial and common peroneal
nerves just above popliteal fossa;
innervates semitendinosus,
semimembranosus and biceps femoris
and has articular branches to hip and
knee joints
Branches of Sacral Plexus
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Tibial nerve
Decends through popliteal
fossa and lies on popliteus;
then runs inferiorly with
posterior tibial vessels and
terminates beneath flexor
retinaculum by dividing into
medial and lateral plantar
nerves; supplies posterior
muscles of leg and knee joint
Branches of Sacral Plexus
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Common peroneal nerve
Arises at apex of popliteal fossa and
follows medial border of biceps femoris and
its tendon; passes over posterior aspect of
head of fibula and then winds around neck
of fibula, deep to peroneus longus, where it
divides into deep and superficial peroneal
nerves
Branches of Sacral Plexus
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Deep peroneal nerve
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Arises between peroneus longus and
neck of fibula; descends on interosseous
membrane and enters dorsum of foot
Supplies anterior muscles of leg, and skin
of first interdigital cleft
Superficial peroneal nerve
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Arises between peroneus longus and
neck of fibula and descends in lateral
compartment of leg
Supplies peroneus longus and brevis and
skin on anterior surface of leg and dorsum
of foot