SPINAL CORD
ANATOMY & PHYSIOLOGY
HONORS ANATOMY & PHYSIOLOGY
Spinal Cord

w/spinal nerves
contain neural
circuits that
mediate some of
your most rapid
reactions to
environmental
changes
Protective Structures
2 types of CT coverings surround &
protect delicate nervous tissue
1. bony vertebrae
2. tough CT meninges, w/cushion of CSF

Meninges



3 CT coverings that encircle spinal cord
& brain:
Spinal meninges covers spinal cord
Cranial meninges covers brain
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)
Middle Meninges:
Arachnoid Mater




“spider-like”
deep to dura mater, superficial to pia
mater
contiguous with cranial arachnoid
between dura & arachnoid = subdural
space
Innermost Meninges:Pia mater




“delicate”
thin, transparent CT
adheres to spinal cord & brain
between arachnoid & pia =
subarachnoid space
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
Spinal Cord




cylindrical 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
Spinal Cord: External View

2 obvious enlargements noted:
 cervical
enlargement
 lumbar
enlargement
 C4
– T1
 serve upper limbs
 T9-
T12
 serve lower limbs
Spinal Cord: External View



conus 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
Conus Medullaris
Filum Terminale
Cauda Equina
Spinal Nerves

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
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
31 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
Spinal Nerves

2 bundles of axons, called roots, connect
each spinal nerve to segment of spinal
cord
Spinal Cord Roots
1.
posterior (dorsal) root


2.
only sensory axons
each has dorsal root ganglion containing
cell bodies of sensory neurons
anterior (ventral) root

only motor axons
Internal Anatomy of
Spinal Cord
2 grooves penetrate white matter &
divide it in right & left sides:
1. anterior median fissure

2.
1.
deeper, wider of the 2
1.
shallower, narrow furrow
posterior median sulcus
Internal Anatomy of
Spinal 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 4th ventricle
of brain
Spinal Nerves


& the nerves that branch off them are
part of PNS
emerge from vertebral column thru
intervertebral foramina
Spinal Nerves

typically has 2 connections to spinal
cord
1.
2.

dorsal root (sensory)
ventral root (motor)
classified as “mixed”
Distribution of Spinal Nerves
Spinal Nerve Plexuses

a network of nerves (or veins, or
lymphatic vessels)
Cervical Plexus


supplies skin &
muscles of the
head, neck, &
superior portion
of shoulders,
chest, &
diaphragm
C1 – C 5
Brachial Plexus

supplies the
shoulders &
upper limbs
Lumbar Plexus

supplies
anterolateral abd
wall, external
genitals, part of
lower limb
Sacral Plexus

supplies buttocks,
perineum, &
lower limbs
Dermatomes


cutaneous 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
Reflexes & Reflex Arches
reflex: a fast, automatic, unplanned
sequence of actions that occurs in
response to a particular stimulus
 can be:
1. inborn


2.
pulling hand away from hot stove
learned or acquired

foot on brake when see dog run in front
of car
5 Parts of a Reflex Arc
Stretch Reflex
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
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
Extent Muscle Paralysis
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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
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
Medical Terminology

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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