Week 3 Learning Issues Flashcards
Conus medullaris
cd extent of spinal cord tapers to an end called conus medullaris, located within caudal lumbar (or sacral in some species) vertebrea; includes sacral and cd spinal cord segments
spinal cord enlargements
cervical and lumbar enlargements; process information from thoracic and pelvic limbs
cervical enlargment
associated with the brachial plexsus; SC segments C6-T2
resides within vertebra C5-T1 (in dog)
lumbar enlargement
associated with the lumbosacral plexsus; SC segments L4-S1 involved in pelvic limb innervation and are larger while segments S1-S3 contribute to pudendal and pelvic nerves; spinal cord segments in L4-S3 range reside within vertebrea L3-L5 (dog)
dorsal median sulcus
longitudinal furrow running on dorsal midline of spinal cord (where alar plate grew together and fused)
ventral midline fissure
deep furrow that runs along v midline
dorsolateral and ventrolateral sulci
less striking than dorsal median sulcus and ventral midline fissure; runs length of spinal cord where dorsal and ventral rootlets enter spinal cord
vertebral foramen
ventral body plus dorsal arch of each vertebrea form this
vertebral arch
vertical pedicles and horizantal laminae
laminectomy
excision of laminae or dorsal arch
vertebral canal
sum of vertebral foramina form vertebral canal which surrounds spinal cord
intervertebral foramina
notches at junction of arch and body of each vertebrea create this; this accomindates passage of spinal nerves, arterial spinal branches, and interertebral veins
atlas intervertebral foramina
has 2 IVF to accomidate C1
transverse vertebral foramina
in vertebrea C1-C6 carry vertebral artery, vein, and nerve
dorsal and pelvic sacral foramina
between sacral segments S1, S2, S3; transmit dorsal and ventral branches of sacral spinal cord segments S1 and S2
ligaments of vertebral column
dorsal longitudinal ligament, interarcuate ligament, dorsal atlanto-occipital membrane, intercapital ligmanets
dorsal longitudinal ligament
on floor of vertebral canal, runs length of vertebral column
interarcuate ligament
aka yellow ligament; extends between vertebral arches bridgining interarcuate space, dorsal to vertebral canal
dorsal atlanto-occipital membrane
between arch of atlas and occipital bone
intercapital ligaments
T1-T10 transverse ligaments connect rib heads in pairs, on floor of vertebral canal dorsal to intervertebral discs, makes disc herniation less common in this region
intervertebral disc features
annulus fibrosus, nucleus pulposus, cartilagenous endplate
intervertebral disc
fibrous joints forming articulations between vertebral bodies
annulus fibrosus
fibrous outer capsule formed by concentric layers of collagen fibers with some elastic fibers between them; this is CT located btwn vertebral discs; sacral vertebrea = fused so no discs between them
annulus fibrosus and nucleus pulposus
annulus fibrosus is lateral to nucleus pulposus
nucleus pulposus
gelatinous central region of disc composed of water, proteoglycans, and collagen; this is a martrix which makes it gel like; this is mostly water
fx of nucleus pulposus
functions as shock absorber. It is a remnant of the notocord
cartilagenous endplate
connects IVD to vertebrea and contains blood vessels that supply the IVD
degenerative changes of intervertebral discs
include proliferation and disruption of collagen fibers of annulus, replacement of nucleus pulposus with fibrocartilage, and mineralization of nucleus pulposus. These changes can lead to bulging or extrusion of intervertebral disc material into vertebral canal which can impinge on or damage the spinal cord or nerves within vertebreal canal -> neurological deficits
meninges associated with the spinal cord
meningeal dura, arachnoid, pia matter; no periodstal dura around spinal cord
epidural space
exists in the spinal cord; bounded by meningeal dura on one side and periosteum of vertebrea or ligaments bridiging the space btwn vertebrea (interarcuate ligaments dorsally) on other
what is epidural space filled with
fat and blood vessels
notable epidural space
internal vertebral venous plexus
intrathecal injection
into subarachnoid space
tight junctions and meninges in spinal cord
tight junctions btwn cells of arachnoid cell layer create barrier restricting passage most molecules into underlying CSF; dura matter lacks tight junctions more like CT proper with ECM and fibers occupying spaces btwn cells
dorsal and ventral roots in spinal cord covered by
meniginges
rootlets and roots invested by
pia along their entire course
arachnoid and dura matter cuffs
form around roots as they course toward intervertebral foramina
intradural nerve roots
proximal spina roots are within columnar region of subarachnoid space, run length of vertebral canal
extradural nerve roots
more distal spinal roots in the subarachnoid space within the meningeal cuffs; they are still within the dural cuff but not larger dural sheath surrounding spinal cord
pial structures that anchor/ suspend the spinal cord within the dural sheath
denticuate ligaments and filum terminale
denticulate ligament
thickened projection of pia that attaches to dura/ arachnoid laterally
filum terminale
narrow cord of pia that extends from cd tip of spinal cord and eventually becomes invested by narrow cord of dura
lumbar cistern
surrounds conus medullaris and continues cd to it forms tapering end subarachnoid space; contains spinal roots associated with cauda equina and filum terminale until these structures enter meningeal cuffs
spinal cord segment
each segment has pair of spinal nerves (L and R); spinal nerves formed by merging of D and V roots which arise from mult rootlets
horse spinal cord/ spinal nerve pair formula
C8 T18 L6 S5 Cd5
spinal nerve relationship to intervertebral foramina
spinal nerve C1- exits vertebral canal via lateral vertebral foramen in atlas
spinal nerves C2-C7 exit via IVF cr to nominally corresponding vertebra
spinal nerve C8 exits via IVF cd to vertebra C7
Spinal nerves T1- Cd5 exit via IVF cd to nominally corresponding vertebra
relationship btwn spinal nerves and peripheral nerves in brachial and lumbosacral plexuses
axons from mult spinal nerves rearrange to form peripheral nerves -> given peripheral nerve being associated with multiple spinal cord segments
development effect on spinal cord length relative to vertebreal column length
spinal cord runs length vertebral column and each spinal cord segment develops within vertebrea of sam segment and spinal nerve roots develop in association with each spinal cord segment and psinal nerves exit vertebral canal btwn adjacent vertebrea; spinal cord elongation slows relative to vertebral column elongation and the spatial correspondence is lost and spinal cord is ultimately shorter than vertebral canal so many SC segments located cr to corresponding vertebrea
SC segment differential growth
depending on how much tissue they innervate they undergo differential growth; those supplying limbs = larger in length and diameter
where does spinal cord end
dog/ cat- L6/ L7 vertebral junction
Cow- ends lumbosacral junction
horse- ends about S1 S2 vertebreal junction
spinal nerves and IVF
as segments shift crly DRG and sponal nerves of each segment already encased in IVF so spinal nerves get longer within vertebreal canal spanning distance btwn spinal cord segment from which they arise and IVF through which they exit vertebral canal
cauda equina
includes D and V spinal roots from lumbar, sacral, and cd spinal cord segments that must travel cdly within vertebral canal to reach corresponding IVF
cauda equina location dogs
L7-S3 vertebra and includes L7-S3 nerve roots
dx of vertebral canal within L7-S3 vertebra
can produce sciatic nerve deficits, pelvic and pudendal nerve deficits and caudal nerve deficits
sciatic nerve deficits
(spinal roots L6,L7,S1)
- decreased withdrawl reflex; sensory deficits and motor deficits of pelvic limb
pelvic and pudendal nerve deficits
(spinal roots S1, S2, S3); urinary and fecal incontinence; decreased anal tone and decreased perineal reflex
caudal nerves
(spinal roots Cd 1-5); decreased tail tone, low tail carriage, tail analgesia
lesion within L3-L5 (in dog)
dx within these vertebrea can produce deficits including paralysis/ paresis and analgesia of pelvic limbs, fecal, and urinary incontinence, decreased anal tone and loss of perineal reflex
Major arteries of spinal cord
segmental spinal branches, ventral spinal artery, dorsal spinal arteries
segmental spinal branches
- arise from vertebral artery, costocervical trunk, and segmental vessel, including intercostal, lumbar, and sacral arteries
- enter vertebreal canal alongside spinal nerve and segmntal vein via interververtebral foramina
- divide into D and V branches to supply the D and V spinal arteries respectively
arterial rings on spinal cord surface
connecting D and V spinal arteries are inconsistent in presence and size and give rise to branches supplying peripheral spinal cord
ventral spinal artery
- unpaired artery running length of spinal cord in ventral median fissure
- recieves blood from L and R spinal branches
- sends semgntal branches into ventral median fissure to supply central spinal cord
- continuous with basilar artery cranially
dorsal spinal artery
- irregularly bilateral, do not form a continuous trunk
- supply dorsal spinal cord
vertebral artery
aorta -> brachiocephalic trunk -> subclavian -> vertebral artery
costocervical trunk
aorta -> brachiocephalic trunk -> subclavian -> costocervical trunk
lumbar artery
aorta -> abdominal aorta-> lumbar artery
sacral arteries
aorta -> abdominal aorta -> median sacral artery
intercostal arteries
aorta -> subclavian -> costocervical trunk -> first 3 dorsal intercostal arteries
aorta -> remaning 9 dorsal intercostal arteries
aorta -> subclavian -> internal thoracic artery -> v intercostal arteries
fibrocartilaginous emboli
small pieces of intervertebral disc material from degenerating intervertebral discs that occlude arterioles in spinal cord resulting in ischemic myelopathy; NT supplied by obstructed vessels loose blood supply and undergo necrosis can -> damage spinal cord region
ischemic myelopathy
damage (pathy) to spinal cord (myelo) due to loss of blood supply (ischemia)
intrathecal injection
contrast agent for myelography and CT in SAS space; anything you put in SAS affects brain and spinal cord bc pia matter is v permiable and SAS is continuous between brain and spinal cord
epidural injection
injections of anesthetic agensts; can do anestetic intrathecal injection but its not as common in vet med because risky and hard to hit
CSF collection
from SAS in lumbar and vertebral canal; safer in lumbar area bc better to hit end of spinal cord than brainstem
myelogram
inject contrast material into subarachnoid space
appearance of vertebral canal as seen on myelogram or MRI
CSF is white and in subarachnoid space in both; they look v similar
layers or laminae
discrete regions of grey matter in spinal cord a and cerebral cortex
nuclei
discrete regions of grey matter in spinal cord brainstem and basal forebrain
bundle of axons traveling together in CNS
funiculus (small rope), fascicles (small bundle), peduncle (little foot) or tract
most general term for bundle of axons
tract
neurons organized into
pathways
decussate
cross to contralateral side of brain
somatosensory pathways carrying info for forebrain
cross to contralateral side before reaching forebrain (thalamus and cerebrum);
pathways carrying motor commands from cerebral cortex to brainstem and spinal cord
cross to contralateral side before reaching target LMNs
at level of forebrain representation of sensory information and motor commands
is contralateral
lesions of spinal cord and brainstem
often ipsilateral
lesions of cerebellum
ipsilateral
bilateral information
ex visceral efferent pathway is routinely bilateral so you contact both halves of your bladder simultaneously
somatosensaton
mechanical thermal and chemical stimulation of skin muscle and joints
proprioception
subdivision of somatosensory system; mechanoreceptors in joints tendons and muscles detect position and movement of limbs, trunk, heads, eyes which is used to guide movement
vestibular apparatus
detects position and movement of head to control posture
vision
may be used for cognitive processing, establishing day/ night and seasonal rhythms, guiding visuomotor hebaivors and many other fxs
visceral sensation
mechanical thermall and chemical stimulation occurring w/ in viscera and other internal tissues of body for regulating visceral fx and behavior
specialized receptors in the brain
often located in circumventricular organs, detect circulating hormones, and chemicals, and plasma osmolatiry and temperature in blood that basses through these brain regions
spinal cord mediates
visceral and somatic reflexes largely via spinal nerves
cd brainstem mediates
visceral and somatic reflexes largely via cr nerves and some complex behavior involving sensorimotor integration associated with vision, audition, and vestibular input, gait generation, and autonomic regulation
cerebellum mediates
motor leanring and fine tuning of motor patterns based on sensory feedback
forebrain mediates
context, memory, and other complex internal neural states to regulate and override reflexive behavior (conscious awareness and voluntary behavior) also generates refined visually guided and highly coordinated movements
