W6 Anatomy of the Spinal Cord Flashcards
what different things does the spinal cord process information from?
processes afferent information from muscles, tendons, joints, ligaments, blood vessels, skin and viscera and discharges efferent commands that control muscles and regulate glands
what is the medulla spinalis also known as?
the spinal cord
where does the spinal cord leave the skull from and what does it run through?
leaves from foramen magnum and runs through the vertebral column (from the medulla oblongata to 6th/7th lumbar vertebrae)
what does the centre of the spinal cord contain?
a central canal filled with cerebrospinal fluid and lined with ependymal cells
what do the spinal nerves inervate?
neck, trunk, tail, limbs and caudal and dorsal surfaces of the head
what segments is the spinal cord divided into?
cervical, thoracic, lumbar, sacral and coccygeal
what is the reason for dividing the spinal cord?
divided due to the attachments of dorsal and ventral roots to the cord, each root is made up of thousands of axons
what is the difference between dorsal and ventral roots of the spinal nerves?
dorsal - convey sensory (afferent) input to the spinal cord
ventral - carry motor (efferent) output to the muscles and glands
each spinal cord segment gives rise to what?
gives rise to paired spinal nerves
dorsal and ventral spinal roots arise as a number of rootlets, what else is present on a dorsal root?
a spinal ganglion (cell bodies outside of the spinal cord and brain are called ganglion)
the first how many segments have rootlets that emerge to form spinal roots of the accessory nerve?
the first seven
at what two locations is the spinal cord increased in diameter (seems like a bumps), why is this?
the cervical enlargement that gives rise to nerves that form the brachial plexus that innervates the thoracic limb
the lumbar enlargement which innervates the pelvic cavity and pelvic limbs (segments L5, L6, L7 and part of S1)
what is a nerve plexus?
a complex interwoven network of nerves
what is the brachial plexus formed by?
the ventral branches of C6, C7, C8, T1 and T2
the large somatic nerve plexus gives origin to nerves that supply what?
the thoracic limb
what root/branches innervates epaxial tissues?
dorsal branches
what root/branches innervate hypaxial tissues, including the limbs?
ventral branches
after birth, is there more growth to the spinal cord or the vertebral column?
the vertebral column
all remaining spinal nerves leave the canal through what?
the sacral foramina
how many spinal cord segments does a dog usually consist of?
36 - 8C, 13T, 7L, 3S and 5C
segments are named like vertebrae but in the dog what is there an additional segment of and what portion only has 5 segments?
an extra cervical segment and only 5 caudal segments
the first cervical spinal nerve leaves through where?
leaves through lateral vertebra foramina in the arch of the atlas (hence 7 cervical vertebrae but 8 cervical spinal nerves)
due to a lack of corresponding vertebrae where does spinal nerve C8 leave from?
exits through cranial margin of vertebrae T1
the cervical enlargement is centred where?
at the C6-C7 intervertebral disc
how many sacral segments are located within the L5 vertebra?
three
where does the functional spinal cord terminate?
at L6-L7
what is the end of the spinal cord?
conus medullaris
what is cauda equine?
a thick bundle of elongated caudally streaming spinal roots (‘horses tail’)
what is the filum terminale?
a glial continuation beyond the point of the functional spinal cord, it contains no neural fibers only connective tissue, it is there to stabilise the spinal cord by attaching distally to bony coxes
what does the conus medullaris and filum terminale make up?
the cauda equine
what is the dura mater?
the outermost layers of meninges which is thick and fibrous, the space between the dura mater and the vertebrae is the epidural space
what is the arachnoid membrane?
the middle layer of meninges that is separated from the pia mater by the subarachnoid space that contains cerebrospinal fluid
what is the pia mater?
the innermost layer of the meninges that has elastic and collagen fibers, it is closely attached to the spinal cord and is the most vascular layer
spinal arteries are suspended within small strands of tissue known as?
arachnoid trabeculae (that connects to the pia mater)
what is the subarachnoid space around the spinal cord continuous of?
with the foramen magnum with the brain
the pia mater is thickened bilaterally along the lateral margin of the spinal cord forming what? what are these for?
forms denticulate ligaments that provide stability to the spinal cord
what does grey mater consist of? why is it grey?
consists of neurons, neuroglia, rich blood supply, neuron cell bodies, dendrites and axons, it is grey due to perikaryal
what does white mater consist of? why is it white?
myelinated and non-myelinated axons, it is white due to the lipid composition of the myelin
what is the spinal cord divided into symmetric right and left halves by?
a dorsal and ventral fissure
what is present where dorsal roots enter the spinal cord?
dorsolateral sulcus
what horns is the spinal cord divided into?
dorsal, ventral and lateral
what does the dorsal horn of the spinal cord contain?
cell bodies of the interneurons on which afferent neurons terminate
what does the ventral horn of the spinal cord contain?
cell bodies of the efferent motor neurons supplying skeletal muscles
what originates from the lateral horns of the spinal cord?
autonomic nerve fibers supplying cardiac and smooth muscles and exocrine glands
what are interneurons?
are interposed between a particular input and the resulting output from the spinal cord - some have long or short axons
what are projection neurons?
send axons into white matter to form, generally, cranial projecting pathways - activated by primary afferent neurons in response to stimulation of viscera, muscles etc
what are efferent neurons?
send axons through the ventral roots to innervate muscles and glands they may be classified as somatic or visceral (autonomic)
white mater is organised into tracts that are grouped into columns extending the length of the spinal cord, where do these begin or end?
begins or ends within a particular area of the brain and each is specific in the type of info that it transmits
