Overview of Spinal Cord Segments & Nerve Roots Flashcards
what are afferent nerves
neurons + pathways they form that convey sensory info to spinal cord and ultimately the brain
what are efferent nerves
the neurons and pathways they form that convey the motor stimulus to the muscles
what are fasciculi
nerve bundles forming functional tracts that have common origins and destinations
what is funiculus
each of the three regions which the spinal cord white matter is divided by the points of penetration of the dorsal and ventral nerve roots axons on each side of a segment (dorsal, lateral and ventral)
what is a tract
collection of nerve fibres (nerve bundle) within the funiculi with the same function that originate together and terminate together and don’t synapse en route
what are the spinal cord divisions
from C1-5
C6-T2
T3-L3
L4-S3
where are the two thickenings of the spinal cord
C6-T2 and L4-S3
what is the conus medullaris
caudal elongation of the spinal cord
what is the filum terminale
thin cord of ependymal and glial cells
tethers end of spinal cord to coccygeal (caudal) vertebrae
suspends the cord in the vertebral canal
what is the spinal cord formed by
- neurons + their axons
- neuroglia: supporting cells of the CNS (astrocytes, oligodendrocytes, microglial cells)
what is the area where there is CSF in the spinal cord
central canal
lined by ependymal cells
what is the spinal cord wrapped in
meninges
3 layers of CT
what are the 3 layers of CT on the spinal cord
- dura matter
- arachnoid matter
- pia matter
what are the structures shown


how many segements are there in the dog and cat spinal cord
36 segments
8 cervical, 13 thoracic, 7 lumbar, 3 sacral, 5 caudal
what does each spinal cord segment contain (3)
1 dorsal root & 1 ventral root
- away from cord –> dorsal and ventral root unite spinal nerve
- closer to cord –> each root divides into rootlets
what structures are shown here


what do dorsal roots do
afferent axons enter cord with sensory info
what do ventral root nerves do
efferent axons exit spinal cord with motor info
where are the cell bodies of spinal ganglion
spinal ganglion aka dorsal root ganglion –> cell bodies outside spinal cord
what returns sensory info the the dorsal root
somatic or visceral structures
what does the efferent axons send info to
muscle, gland or organ
how are cell bodies grouped in the ventral root
cell bodies grouped forming ventral horn of spinal cord
what are lower motor neurons
efferent neurons
how is the grey matter organized in the cord
general somatic afferent =
general proprioception =
= spinal ganglion
general visceral afferent =
general visceral efferent =
= ventral horn
general somatic efferent =
what are the structures shwon
dorsal root
spinal ganglion

what segment of the spinal cord is this

C3 because smaller ventral horn
what segment of spinal cord is this

C6-T2 –> cervial intumescence
what segment of the spinal cord is this

T3-L3
smaller ventral horn
what segment of the spinal cord is this
L4-S3
lumbosacral intumescence
what are the white matter organization in the spinal cord

I: dorsal funiculus: ascending sensory tracts (proprioceptive, tactile, nociceptive)
II: lateral funiculus (proprioceptive, tactile, nociceptive, thermal) + descending motor tracts (facilitating extensor mm activity)
III: ventral funiculus: descending motor tracts + some ascending sensory (nociceptive –> pain)
what is dura mater
dense connective tissue
what is the function of dura mater
adhere to periosteum on inner surface of cranial wall & floor of C1 and C2 vertebrae
what separates dura mater from periosteum within vertebral canal
epidural space –> fat and bloow vessels
caudally combines with filum terminale to attach to first caudal vertebra (filum of dura mater)
what are the structures shown


what are the structures shown


what are the structures shown


what is the arachnoid
delicate collagenous connective tissue
what is the function of the arachnoid
encloses CSF in subarachnoid space
close contact with dura mater due to CSF pressure
numerous fine filaments which blend with pia mater
what is the pia mater
thin layer of CT (thicker than arachnoid)
what are the inner and outer surfaces of pia mater
outer surface blends with filaments of arachnoid
inner surface fused to brain and spinal cord
what is midway between successive spinal nerve roots
midway between successive spinal nerve roots –> pia mater & arachnoid attach to dura mater = denticulate ligament
what are the functions of meninges
- physical support
- encloses CSF circulation
- CSF production (42% in leptomeningeal capillaries)
what are the clinical significance of the meninges
CSF collection
myelography
what are the diseases of meninges
- meningitis
- neoplasia (meningioma)
why is the development of spinal cord segments and vertebral column closely related
spinal nerves exit vertebral canal via intervertebral foramen
except: C1 nerve - lateral vertebral formina of atlas
spinal cord segments does not equal # of vertebrae
how is the spinal cord segment divided
pair of dorsal and ventral roots
pair of spinal ganglia
pair of spinal nerves
boundaries between segments –> midway between attachments of most caudal and most cranial rootlets of adjacent dorsal roots
where is the brachial plexus located
C6-T2
where is the suprascapular nerve and what does it innervate
(C5), 6, 7
innervates supraspinatus muscle
infraspinatus muscle
where is the subscapular nerve and what does it innervate
C6, 7
innervates subscapularis muscle
where is the musculocutaneous nerve and what does it innervate
C6, 7, 8
biceps brachii
brachialis
coracobrachialis
where is the axillary nerve and what does it innervate
C6, 7, 8
deltoideus
teres major
teres minor
(subscapularis)
where is the radial nerve and what does it innervate
C7, 8 T1 (2)
triceps brachii
extensor carpi radialis
ulnaris lateralis
common digital extensor
lateral digital extensor
where is the median nerve and what does it innervate
C8, T1, (2)
flexor carpi radialis
superficial digital flexor
(deep digital flexor)
where is the ulnar nerve and what does it innervate
C8, T1 (2)
flexor carpi ulnaris
deep digital flexor
how is the brachial plexus function tested
- flexor (withdrawl) reflex
sensory: varies with area stimulated
motor: musculocutaneous, axillary, median, ulnar, radial - biceps reflex
sensory & motor: musculocutaneous
- triceps reflex
sensory & motor: radial
where is the lumbosacral plexus located
L4-S3
where is the femoral nerve located and what does it innervate
femoral L4,5,6
Iliopsoas
quadriceps
sartorius
where is the obturator nerve located and what does it innervate
L4, 5, 6
external obtruator
pectineus
graciis
adductor
where is the cranial gluteal nerve located and what does it innervate
L6, 7, S1
middle gluteal
deep gluteal
tensor fascia lata
where is the caudal gluteal nerve located and what does it innervate
L7, S1, 2
superficial gluteal
(middle gluteal)
where is the sciatic nerve located and what does it innervate
L6, 7, S1, (2)
biceps femoris
semimembranous
semitendinosus
common peroneal –> peroneus longus, lateral digital extensor, long digital extensor, cranial tibial
tibial –> gastrocnemius, popliteus, superficial digital flexor, deep digital flexor
where is the pudendal nerve located and what does it innervate
S1, 2, 3
caudal rectal –> external anal sphincter
what are the functional testing associated with lumbosacral plexus
- flexor (withdrawal) reflex
sensory & motor: sciatic nerve
- patellar reflex
sensory & motor: femoral
- perineal reflex:
sensory & motor: pudendal