Spinal Cord Anatomy Flashcards
Thoracic vertebrae parts
-Body- held together by ligaments
-Spinous process- prominent in T1,T2 which makes it easier to count
-transverse process (lateral sides)
Intervertebral disk
-acts as a cushion
-gel like substance which comes out when you herniate a disc, which applies pressure to spinal cord
Vertebral column
-spinal cord runs through the vertebral column and nerves exit at intervertebral foramen
-vertebrae transition directions at T11 (anticlinal vertebra- all spinous process point cranial after this point)
Special vertebrae
-C1 (atlas)- has very wide transverse processes and is generally wider/flatter, prominent spinal process not present
-C2 (axis)- dens extends cranially; prominent spinal process not present
CNS vasculature
-the spinal cord supplied by segmental vessels (Aorta) and the vertebral arteries (vertebral, costocervical, intercostal, lumbar)
-dorsal: dorsal spinal arteries (paired)
-ventral: ventral spinal
artery (single;midline)- most of blood supply from ventral side
-the blood supply from the brain comes from the ventral aspect (basilary artery and internal carotid)
Greatest blood supplier
-ventral spinal artery supplied most of the spinal cord (~2/3rds)
Segments of spinal cord
-cervical
-thoracic
-lumbar
-sacral
Where do spinal nerves exit?
-exit vertebral canal via intervertebral foramen
Cervical and lumbosacral enlargements
-important for the limbs, more neurons present, especially for the dexterity required
Peripheral nerves
-mixed nerves (dorsal sensory root and ventral motor root)
-these mixed nerves will then give rise to a dorsal and ventral branch (“rami”) to innervate targets
Conus medularis
-end of spinal cord
-segments are compressed as you move caudally and multiple segments fit within a single vertebrae
-the spinal cord (dura mater) ends, but these nerves will extend out and come out further down=cauda equina
Cauda Equina
-the lumbosacral junction marks the end of the spinal cord but the cauda equina continues as spinal nerves that move caudally to exit at their corresponding vertebral segment (spinal nerves are outside of the CNS because outside the dura mater)
considered a group of nerves
Nerves of cauda equina
-nerves will contributes to innervation of the pelvis and perineum
-S1-S3 form the pudendal nerve, which is a convenient location for local anesthesia
**a distal lumbar or sacral fracture will damage all of these nerves together (L7-Ca5) and result in cauda equina syndrome= damage to PNS, so no CNS signs
Meninges in spinal cord
-the dura mater is not fused to periosteum in vertebral column (whereas it is in the brain)
Epidural space
-the space between the dura and vertebral body
-space contains fat, blood vessels, and spinal nerves
Anesthesia in epidural space
-anesthetic solution will diffuse locally cranial/caudal through the epidural space to bather the spinal nerves and provide the nerve block
-most local anesthetics agents work by inhibiting sodium channels, therefore action potentials (nerve conduction) is stopped
**typically done caudally to anesthetize structures of the cauda equina (perineum) without causing motor deficits to pelvic limbs
Subdural space
-this is the potential space between the arachnoid and the dura
-can be a site of hemorrhage and subsequent CNS compression
Subarachnoid space
-space created by the arachnoid trabeculae
-filled with CSF (collection sites for CSF)
Locations of spinal taps
1.cisternal tap (cerebellomedullary cistern, atlanto-occipital site)- used when brain lesion
2. lumbar tap (caudal lumbar site)- used when spinal cord lesion
Tap where fluid would drain from the injury
How much CSF to collect?
-collect 2 tubes (1ml/5kg)
-used for cytology or protein analysis
Spinal cord injuries
-soft tissue trauma (IVDD)
-vascular injury
-fracture
-disease (demyelination, cell death, electrolyte imbalance)
-toxin/infection
-neoplasia
Difficulties of treating spinal cord injuries
-CNS tissues are very delicate and damaged more easily
-neural tissue has limited regenerative capacity
-many drugs used to treat other soft tissue injuries are ineffective in the CNS due to the protective BBB and B-CSF barriers
Spinal cord compression
-compression of spinal cord or peripheral nerves will cause neurological deficits and/or pain
-from herniation of disc
IVDD (intervertebral disc disease)
-common in small breed dogs, middle-aged to geriatric
-Breeds: daschunds, bulldogs, boston terriers, beagles, shih tzu, corgis
Wobbler’s syndrome
-cervical spondylomyelopathy
-unknown cause, but may be due to growth discrepancy between spinal cord and vertebral column resulting in a narrowed spinal canal and/or compression of the cervical cord OR from bony changes to the vertebral column that cause compression
-Breeds: Dobermans, great danes, weimaraners, other giant breeds
