The Spinal Nerves

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The Spinal Nerves

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General description

• 31 pairs spinal nerves
• 8 cervical, 12 thoracic, 5 lumbar, 5 sacral,
  and 1 coccygeal nerve.
• 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.

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• Functional components
• 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

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• Branches of spinal nerves
• Anterior branch largest , innervates
  anterolateral body wall and limbs,the great nerve
  plexus, e.g. the cervical, brachial, lumbar, and
  sacral, are formed by anterior rami
• Posterior branch innervates the back of the
  trunk
• Communicating branch connect the spinal nerve to
  the sympathetic trunk
• Meningeal branch re-enters vertebral canal
  through intervertebral foramen to dura mater

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Cervical plexus ??

• 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

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• Branches
• Cutaneous branches
• 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

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• Muscular branches supply the deep muscles of
  neck
• Phrenic nerve (anterior rami of C3-C5) to
  diaphragm (motor and sensory)
• Descends over scalenus anterior to enter thorax
• 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.

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Brachial plexus ??

• Formation
• Formed by anterior rami of C5-C8 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

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• Musculocutaneous nerve
• Distribution Biceps brachii, brachalis and
  coracobrachialis BBC nerve skin on anterior
  aspect of forearm

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• Median nerve
• Distribution Flexor of forearm except
  brachioradialis, flexor carpi ulnaris and ulnar
  half of flexor digitorum profundus, thenar except
  adductor pollicis, first two lumbricals skin of
  thenar, central part of palm, palmar aspect of
  radial three and one-half fingers, including
  middle and distal fingers on dorsum

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• Ulnar nerve
• Distribution Flexor carpi ulnaris, ulnar half of
  flexor digitorum profundus, hypothenar muscles,
  interossei, 3rd and 4th lumbricals and adductor
  pollicis 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

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• Radial
• Distribution Extensor muscles of arm and
  forearm, brachioradialis skin on back of arm,
  forearm, and radial side of dorsum of hand and
  radial two and one-half fingers

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• Axillary ???
• 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

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Anterior branches of thoracic nerves

• 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
• T2 Sternal angle
• T4 Nipple
• T6 Xiphoid process
• T8 Costal arch
• T10 Umbilicus
• T12 Midpoint between umbilicus and symphysis
  pubis

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Lumbar plexus

• Formation formed by anterior rami of L1-L3, a
  part of anterior rami of T12and L4
• Position lies within substance of psoas major
• Branches
• Iliohypogastric
• Ilioinguinal
• Lateral femoral cutaneous
• Femoral
• Obturator
• Genitofemoral

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• Femoral
• Runs downward and laterally between psoas and
  iliacus, 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
• Enters thigh through obturator foramen
  supplies medial group of muscles of thigh,
  obturator externus, and skin of medial side of
  thigh

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Sacral plexus ??

• 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

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• Branches
• Superior gluteal
• Pudendal
• Posterior femoral cutaneou
• Sciatic

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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

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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

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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
• Deep peroneal nerve
• 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
• 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

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• Superficial peroneal

Deep peroneal