Spinal Cord Anatomy Flashcards
What areas are the spinal cord divided into
Cervical, thoracic, lumbar, sacral and coccygeal
Why do the individual segments of spinal cord not lie within corresponding vertebra
Because the vertebral column grows fast than the spinal cord, therefore most spinal nerves pass caudally before leaving vertebral canal
What is the conus medullaris
caudal extent of the spinal cord
Where is the caudal extent of the spinal cord in dog, horse, pig and cat
Dog: L6-L7
Horse: S1
Pig: S3
Cat: S1
What does caudal equine mean
Horse tail is made up of nerve roots
What is filum terminale
Caudal extension of pia-arachnoid matter to attach to the dura mater
Describe the cervical spinal cord in the dog
C1-C8
Passage of fiber tracts, neck area is well innervated, supplies spinal component of CN11
What is the cervical enlargement
C6-T1/T2
Has as much white matter as regular cervical spinal cord, large grey matter though because of brachial plexus for forelimb
Describe the thoracic spinal cord
T1-T13
Reduction in ventral grey horn because fewer muscles to innervate in trunk
- lateral horn is for autonomic motor neuron
Describe lumbar spinal cord
L1-L7
- larger with large grey matter because of hind limbs
- lateral grey horn is the location of autonomic neuron cell bodies
What is the lumbrosacral enlargement
L3-S3
- large with a lot of grey matter because of lumbosacral plexus
Describe the sacral spinal cord
S1-S3
- decrease in both grey and white matter because of termination of fibers in the lumbosacral enlargement
- little innervation
Describe the coccygeal spinal cord
C1-C5
- small with little innervation
Where are autonomic neuron cell bodies located in spinal cord
Lateral grey horn
What is in the dorsal (posterior) grey horn
Sensory nerve fibers synapse with interneuron
What is in the ventral (anterior) grey horn
Two motor components of ventral root
- alpha efferent is the somatic motor component
- gamma efferent is smaller and goes out through the ventral root to go to the stretch receptor of muscle spindles
Where is white matter in the spinal cord
Contained in posterior, lateral and anterior funiculi
What are fasciculi
Specific functional groups within funiculi
What two fasciculi are in the posterior funiculus
Medial –> fasciculus gracilis
Lateral –> fasciculus cuneatus
What is fasciculus gracilis
Slender, lower part of body
What is fasciculus cuneatus
Wedge-shaped, upper part of body
What is carried by the fibers in fasciculi
Sensory modality of conscious proprioception
Ie. your feet on the ground and you know where it is, your position in space.
(Note: when you don’t want to think about this you turn it to your cerebellum for unconscious proprioception)
What is white matter formed from and where is it in the cord
Formed from the marginal layer and occurs in the peripheral area of cord
In what ways does the internal structure or cross section of the spinal cord vary from one area to another
- diameter
- relative amount of gray and white matter
- size of ventral grey horn
How does the cervical part of the spinal cord compare to other areas
- largest in diameter
- large amount of white matter (fiber tracts from brain to spinal cord and vice versa)
- large amount of grey matter (neck is well innervated)
How does the size of the grey matter in the cervical enlargement relate to the mass of muscles innervated
Direct relationship
How does the thoracic part of the spinal cord compare to other areas
- more circular in shape
- reduced amount of grey matter, especially in ventral grey horn
- intermediate/lateral grey horn
How does the lumbar part of the spinal cord compare to other areas
- larger than thoracic
- increase in amount of grey matter because larger muscle innervation
What type of fiber is the spinal nerve
Mixed fiber
- somatic afferent, visceral efferent
- somatic efferent, visceral efferent
- preganglionic fiber of ANS
What is endoneurium
CT surrounding a single nerve fiber
What is perineurium
CT surrounding a group of nerve fibers, could be afferent or efferent
What is epineurium
Heavy CT surrounding several groups of nerve fibers
