Post on 15-Jan-2016
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 vertebrae2. 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
C4 – T1 serve upper limbs
lumbar enlargement 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
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 only sensory axons each has dorsal root ganglion containing
cell bodies of sensory neurons
2. 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 fissure1. deeper, wider of the 2
2. posterior median sulcus1. shallower, narrow furrow
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 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 cord1. dorsal root (sensory)2. 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
pulling hand away from hot stove
2. 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
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
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