Spinal Cord and Spinal Nerves PPT

June 15, 2012 | By | Reply More

Spinal Cord and Spinal Nerves PPT

Adult spinal cord:

Resides inside vertebral canal
Extends to L1/ L2
31 segments, each associated with a pair of dorsal root ganglia
Two enlargements
1. Cervical Enlargement

Gray matter expanded to incorporate more sensory input from limbs and  more cell bodies for motor control of limbs

Spinal Meninges

Three membranes surround all of CNS

1) Dura mater – “tough mother”, strong

2) Arachnoid  meninx – spidery looking, carries blood vessels, etc. Subarachnoid space

3) Pia mater – “delicate mother”, adheres  tightly to surface of spinal cord

Inferior End of Spinal Cord

Conus medullaris – inferior end of spinal cord proper
Cauda equina – individual spinal nerves within spinal canal
Filum terminale – filamentous end of meninges, “tie-down”
Lumbar Puncture (= Spinal Tap)

For clinical examination of CSF or administration of radiopaque  dyes, drugs and sometimes anesthetics

However: mostly “epidurals” for anesthetics

Organization of Cord Cross Section

Gray matter – interior horns

posterior –  somatic and visceral sensory nuclei

anterior (and lateral) gray horns – somatic and visceral motor control

gray commissures – axons carrying information from side to side


 White matter – tracts or columns

posterior white column –

anterior white column

lateral white column

anterior white commissure



ascending tracts – sensory toward brain

descending tracts – motor from brain

Peripheral Nerves

Definition: bundles of axons.  AKA tracts in CNS

Organization – coverings:

Epineurium       wraps entire nerve

Perineurium      wraps fascicles of tracts

Endoneurium     wraps individual axons

Anatomy of a Peripheral nerve


sensory – afferent

motor – efferent

mixed – contains axons of both


Organization of Spinal Nerves:

1. Root – inside vertebral canal

a. dorsal sensory root with a ganglion

b. ventral motor

2. Mixed spinal nerve

3. Rami

a. dorsal – mixed to skin and muscles of back

b. ventral – mixed  “spinal nerve” to ventrolateral body surfaces and limbs

c. white ramus communicans  motor ANS

d. gray ramus communicans  motor ANS


Sensory innervations by specific spinal nerves » Each pair of spinal nerves monitors specific region of body surface.
Clinical significance ?
4 Principal Plexuses

Braids of ventral rami of cervical,  thoracic, lumbar or sacral  spinal  nerves

Cervical Plexus – Phrenic nerve – innervates diaphragm


Fast, stereotypical, inborn, protective actions

Occur at spinal cord or brainstem levels

May be either monosynaptic or polysynaptic

All require

a. stimulus at receptor

b. sensory information relay

c. processing at CNS level

d. activation of motor response

e. response of peripheral effector


Spinal Cord and Spinal Nerves PPT  CLICK HERE to download


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Category: Medical

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