SPINAL CORD ANATOMY & PHYSIOLOGY - PowerPoint Presentation

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SPINAL CORD ANATOMY & PHYSIOLOGY

HONORS ANATOMY & PHYSIOLOGY

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Spinal Cordw/spinal nerves contain neural circuits that mediate some of your most rapid reactions to environmental changes

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Protective Structures2 types of CT coverings surround & protect delicate nervous tissue

bony vertebrae

tough CT

meninges

, w/cushion of CSF

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Meninges

3 CT coverings that encircle spinal cord & brain:

Spinal

meninges

covers spinal cord

Cranial

meninges

covers brain

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Meninges Layers: Dura Mater

“tough mother”

most superficial layer

made of dense, irregular CT

continuous with cranial

meninges

forms sac from foramen magnum

 S2

layer of adipose tissue between

dura

mater & wall of vertebral cavity (

epidural space

)

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Middle Meninges:

Arachnoid

Mater

“spider-like”

deep to

dura

mater, superficial to

pia

mater

contiguous with cranial

arachnoid

between

dura

&

arachnoid

=

subdural space

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Innermost Meninges:Pia mater

“delicate”

thin, transparent CT

adheres to spinal cord & brain

between

arachnoid

&

pia

=

subarachnoid space

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Spinal Tap

aka lumbar puncture

long needle inserted into subarachnoid space

adults: between L3 –L4 or L4 – L5 (inferior to lowest portion of spinal cord)

purpose: withdraw CSF for

diagnostic purposes

insert antibiotics/contrast media for

myelography

/ anesthetics/ chemotherapy

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Spinal Cordcylindrical with flattening of its AP diameter

adults:extends

from medulla oblongata

 L2 vertebra

newborns: extends to L3 or L4

elongation of spinal cord stops ~age 3-4 but growth of vertebral column continues

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Spinal Cord: External View2 obvious enlargements noted:

cervical enlargement

C4 – T1

serve upper limbs

lumbar enlargement

T9- T12

serve lower limbs

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Spinal Cord: External Viewconus

medullaris

: tapered conical structure of spinal cord below lumbar enlargement ending @ L1 – L2

filum

terminale

: extension of

pia

mater extends inferiorly & anchors cord to coccyx

cauda

equinae

: “horse tail” nerves that arise from lumbar, sacral, &

coccygeal

portions of spine

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Conus Medullaris

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Filum Terminale

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Cauda Equina

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Spinal Nerves31 pairs spinal nerves emerge thru

intervertebral

foramen

8 pair cervical nerves: C1 – C8

12 pair thoracic nerves: T1 - T12

5 pair lumbar nerves: L1 – L5

5 pair sacral nerves: S1 – S5

1 pair

coccygeal

nerves: Co1

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Spinal Nerves2 bundles of axons, called roots, connect each spinal nerve to segment of spinal cord

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Spinal Cord Roots

posterior (dorsal) root

only sensory axons

each has dorsal root ganglion containing cell bodies of sensory neurons

anterior (ventral) root

only motor axons

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Internal Anatomy of Spinal Cord

2 grooves penetrate white matter & divide it in right & left sides:

anterior median fissure

deeper, wider of the 2

posterior median

sulcus

shallower, narrow furrow

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Internal Anatomy ofSpinal Cord

gray matter shaped like “H” or a butterfly & is surrounded by white matter

gray

commissure

forms the “H” crossbar

central canal

small hole in its center

extends entire length of spinal cord

filled with CSF

@ superior end is contiguous with 4

th

ventricle of brain

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Spinal Nerves

& the nerves that branch off them are part of PNS

emerge from vertebral column thru

intervertebral

foramina

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Spinal Nervestypically has 2 connections to spinal cord

dorsal root (sensory)

ventral root (motor)

classified as “mixed”

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Distribution of Spinal Nerves

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Spinal Nerve Plexuses

a network of nerves (or veins, or lymphatic vessels)

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Cervical Plexussupplies skin & muscles of the head, neck, & superior portion of shoulders, chest, & diaphragm

C1 – C 5

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Brachial Plexussupplies the shoulders & upper limbs

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Lumbar Plexussupplies

anterolateral

abd

wall, external genitals, part of lower limb

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Sacral Plexussupplies buttocks, perineum, & lower limbs

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Dermatomescutaneous

area developed from one embryonic spinal cord segment & receiving most of its sensory

innervation

from one spinal nerve

knowing which spinal cord segments supply each dermatome makes it possible to locate damaged regions of the spinal cord

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Reflexes & Reflex Archesreflex

: a fast, automatic, unplanned sequence of actions that occurs in response to a particular stimulus

can be:

inborn

pulling hand away from hot stove

learned or acquired

foot on brake when see dog run in front of car

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5 Parts of a Reflex Arc

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Stretch Reflex

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Pupillary Light Reflex

pupils of both eyes decrease in diameter when either eye is exposed to light

absence of a normal

pupillary

light

refex

indicates possibility of brain damage or injury

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Spinal Cord Injuries

most due to trauma

cervical, lower thoracic, upper lumbar most common regions involved

paralysis

depends on location, extent of damage

monoplegia

: 1 limb

paraplegia

: both lower limbs

hemiplegia

: upper limb, trunk, lower limb on 1 side of body

quadriplegia

: all 4 limbs & trunk

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Extent Muscle Paralysis

C1 – C3: no function neck down, requires ventilator to breathe

C4 – C5: diaphragm, allows breathing

C6 – C7: some arm, chest, allows breathing, moving wheelchair

T1 – T3: intact arm function

T4 – T9: control of trunk above umbilicus

T10 – L1: most thigh muscles, walk w/long leg braces

L1 – L2: most leg muscles, walk w/short leg braces

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Shingles acute infection of PNS

caused by herpes zoster (chicken pox)

virus stays in posterior root ganglion

becomes reactivated normally immune system will prevent it from spreading

reactivated virus can overcome weakened immune system

 leaves ganglion  travels down sensory neurons supplying skin

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Medical Terminology

meningitis:

inflammation of

meminges

due to infection, bacterial (worse) or viral, vaccine protests against some bacterial causes: headache, N/V, fever, stiff neck

neuralgia:

pain along a sensory nerve, trigeminal neuralgia

neuritis:

inflammation of 1 or several nerves

paresthesis

:

abnormal sensation

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