spinal cord anatomy Flashcards
what is the purpose of a complete physical and neurologic exam
- to narrow the area of neurologic damage
- localization is not the same as diagnosis of disease
what is the spinal cord:
a continuation of the brainstem out of the foramen magnum
how far does the spinal cord travel in dogs
the spinal cord travels down to the 6th/7th lumbar vertebrae
how are segments of the spinal cord defined
segments are defined by the attachment of the dorsal and ventral roots of the spinal nerves
how many pairs of nerve roots are there in a spinal cord
there are 36 pairs of nerve root bilaterally
what is the conus medullaris
- terminal tapering of the cord
- level of termination varies among species
(T/F)the nerve root of the spinal cord always mirror the exact level of the same vertebrae
F: the more you move caudally within the vertebral canal, the spinal nerves must extend further caudally in order to pass through their designated intervertebral foramina
Cauda Equina
where the spinal “cord” no longer exists and there are only individual nerves within the spinal canal (looks like a horse’s tail)
why is knowing the location of the conus medullaris is clinically relevant
when withdrawing CSF fluid, or application of an “epidural” anesthetic, we often insert the needle caudal to the conus medullaris to avoid puncturing the spinal cord
where is the conus medullaris in cats
L7-S3
where is the conus medullaris Dog
L6-L7
where is the conus medullaris Pig
S1-S2
where is the conus medullaris Ox
L6-S1
where is the conus medullaris horse
S2
how is the number of spinal cord segments related to the number of vertebrae in each region
The number of thoracic, lumbar, and sacral spinal cord segments is consistent with the number of vertebrae in these regions
how many cervical vertebrae and cervical spinal segments are in all mammals
- 7 cervical vertebrae
- 8 cervical spinal segments/nerves
where does the first pair of cervical spinal nerves emerge
through the lateral vertebral foramina of the atlas
where do cranial nerve 2-8 emerge from
- CSN 2-8 emerge cranial to their corresponding cervical vertebrae
- CSN 8 emerges caudally to cervical vertebra 7
where will thoracic and lumbar spinal nerves emerge from
thoracic and lumbar spinal nerves will emerge caudal to their corresponding vertebrae
where do the first two sacral spinal nerves in the dog emerge
- the sacral foramina
- dorsal foramina
- pelvic foramina
where does the third sacral spinal nerve in the dog emerge
between the intervertebral foramen between the sacrum and the first caudal vertebra
Pia mater of the meninges
thin layer of connective tissue immediately adjacent to the surface of the spinal cord
Arachnoid of the meninges
thin loose connective tissue directly connected to the dura
Sub-arachnoid space
is the space beneath the arachnoid
Dura mater of the meninges
tough outer layer
what fluid is found in the subarachnoid space
CSF fluid is found here
what is inside the epidural space
the epidural space is fat-filled space between the vertebra and dura
what is the function of the Denticulate ligaments
they anchor the spinal cord along its length on each side to the dura mater
what are the 5 areas of gray matter in a cross-section of a spinal cord
- Dorsal horn
- Intermediate substance
- Lateral horn
- Ventral horn
- Central gray
what are the 3 regions of white matter
- dorsal funiculus
- lateral funiculus
- ventral funiculus
Somatotopy
point-for-point correspondence of a specific body part to a specific region of the CNS
Ascending tracts transport _________ info from the _______ to the _______
Ascending tracts transport sensory info from the spinal cord to the brain
where is the ascending tract usually located in the funiculi
the ascending tract is generally located in the dorsal and lateral (external) funiculi
what information is transported in the descending tract
- commands from the brain to the spinal cord
- initiates motor events
- regulates motor events
where are the descending tracts generally located in the funiculi
the descending tracts are generally located in the ventral and lateral (interior) funiculi
Proprioception:
the perception of stimuli in relation to the body’s position, motion, and equilibrium
In the spinal cord segments dorsal and ventral roots joint to produce
spinal nerves
what is a spinal cord segment
the region of the spinal cord where the one set dorsal and ventral rootlets attach
what is the function of the dorsal roots
bring sensory fibers into the spinal cord
what is contained in the dorsal root ganglia
contains cell bodies of sensory (afferent) neurons
what is the function of ventral roots
ventral roots bring motor (efferent) nerve fibers from cell bodies in the spinal cord to the effector structures (organs,muscles, glands)
- Branches of the spinal nerve:
- Dorsal branch leads to
- dorsal branch
- epaxial sensory and motor
- meningeal branch
- epaxial sensory and motor
- Branches of the spinal nerve:
- ventral branch leads to
- ventral branch leads to
- hypaxial sensory and motor
- Branches of the spinal nerve:
- Ramus communicans leads to
- ramus communicans leads to
- connects to the sympathetic trunk/chain of ganglia (visceral efferent and afferent)
what is another name for the ramus commuicans
communicating branch
what is the main function of the spinal cord
transmission of info to and from the brain
how does the spinal cord transmit sensory information
- sensory(afferent) input to everything but the head. Receives info from the peripheral nerves by the way of the dorsal roots
- the afferent info comes from the receptors throughout the body viscera
- Delivers info about the sensation of touch, proprioception, and pain
How does the spinal cord transmit motor info
- Motor(efferent) commands are sent to muscle and glands via ventral roots
- commands from the brain travel in specific white matter pathways separate from the afferent sensory tracks
what is reflex control
somatic and visceral tissues unconscious reaction to sensory input from the environment
what 2 possible functions does an interneuron have (and often accoplishes both)
- integrate the afferent stimulus to induce local reflex
- stimulate muscles and glands
- relay the information to an afferent neuron for conscious perception
what are the six functional divisions of the spinal cord based on structures supplied
- cranial cervical region
- cervicothoracic region
- thoracolumbar region
- lumbosacral region
- sacral region
- caudal region
which vertebra make up the cranial cervical region
C1-C5
what does the nerves of the cranial cervical region innervate
innervation to axial muscles and skin of cranial cervical region
which vertebra make up the cervicothoracic region
C6-T2
what does the cervical intumescene in the cervicothoracic region supply
- brachial plexus
- hence the innervation of the thoracic limb muscles and skin
intumescence
enlargement
what other structures does the cervicothoracic region innervate other than those associated with the cervical intumescence
- innervation of regional axial muscles and skin
- Sympathetic innervation to the head/eye (T1-T2)
which vertebra make up the thoracolumbar region
T3-L3
what does the thoracolumbar region innervate
- innervation of regional muscles and skin
- also contains preganglionic sympathetic neurons (“thoracolumbar”)
which vertebra make up the lumbosacral region
L4-S4
what does the lumbar intumescence in the lumbosacral region supply
the lumbosacral plexus, hence the innervation to the skin and muscles of the pelvic limb
what other structures does the lumbosacral region innervate other than the structures associated with the lumbar intumescence
- innervation of regional axial muscles and skin
- Partial supply to the bladder and perineum
which vertebra make up the sacral region
S1-S3
What parasympathetic innervation does the sacral region do
innervation to the viscera of the pelvis and urinary bladder (pelvic nerve)
what other innervation does the sacral region have other than the parasympathetic with the pelvic nerve
innervation to the perineum muscle and skin as well as external anal sphincter and urethral sphincter (pudendal nerve)
