C: Spinal cord and Spinal Nerves Anatomy Flashcards
The vertebral column contains how many vertebrae?
30 (some say 33) 7 Cervical 12 Thoracic 5 Lumbar 5 Sacral 1(/4) coccygeal
How many spinal cord segments are there?
31
How many spinal nerves does each spinal cord segment give rise to?
1 pair of segmental spinal nerves
How many spinal nerves are there, and of what type?
31 8 cervical 12 thoracic 5 lumbar 5 sacral
Where does C1 spinal nerve pass out of the spinal cord?
Between the base of the skull and C1 vertebra
Where do the spinal nerves pass out relative to their corresponding vertebra?
Cervical spinal nerves pass out the vertebral column superior to the pedicles of their corresponding vertebra
Thoracic, lumbar and sacral and coccygeal pass out inferior to the pedicles of their corresponding vertebra
Where does spinal nerve C8 pass out of the vertebral column?
Between C7 and T1 vertebra
Where is the transition in nomenclature of nerves?
Between C7 and T1
How thick is the spinal cord?
About the thickness of a little finger
What 2 enlargements can be seen in the spinal cord and why?
Cervical enlargement - gives rise to the brachial plexus
Lumbar enlargement - gives rise to nerves supplying lower limb
What is the cauda equina?
Dorsal and ventral roots of lower lumbar and sacral and coccygeal segmental spinal nerves travelling to their corresponding vertebra
What is the filum terminale?
Fine strand coming from the conus medullaris which travels and attaches to the coccyx, its an extension of pia mater and a remnant of the developing spinal cord
How many layers of meninges surround the spinal cord?
3
What 3 layers of meninges surround the spinal cord?
Dura mater (meningeal layer)
Arachnoid mater adhered tightly to the dura mater due to pressure of underlying CSF
Pia mater
What separates the dura mater from bone?
Fat-filled epidural space
What is the nature of the dura mater supplying the spinal cord?
Tough, fibrous
What is the nature of the arachnoid mater surrounding the spinal cord?
Thin, delicate
What is the nature of the pia mater surrounding the spinal cord?
Thin layer attached to the surface of the cord
What lies between the arachnoid mater and pia mater?
Subarachnoid space containing CSF
How does CSF enter the subarachnoid space surrounding the spinal cord?
By leaving the lateral and median apertures of the ventricular system
What are denticulate ligaments?
Extensions of the pia mater, extending laterally from the spinal cord to attach to the walls of the spinal canal
What is the function of the denticulate ligaments?
To stabilise the spinal cord and prevent rotatory movement
The periosteal layer of dura mater surrounding the brain doesnt go on to surround the spinal cord, what is it instead continuous with?
When it reaches the base of the skull it is continuous with the periosteum of the skull
Dorsal and ventral rootlets contain what kinds of info?
Dorsal rootlets - sensory
Ventral rootlets - motor
Dorsal and ventral rootlets carry what kind of fibres?
Ventral carry efferent fibres
Dorsal carry afferent fibres
What is a ganglion?
A collection of cell bodies in the PNS
What does a dorsal root ganglion contain?
Cell bodies of primary sensory fibres which are single fibres carrying info from a particular area of skin and have their cell bodies in the dorsal root ganglion and then a short projection from the dorsal root ganglion to the spinal cord
What is the difference between and epidural and a spinal anesthetic?
Epidural - goes into the epidural space and does not pass through the dura mater, can be specific to certain spinal nerves
Spinal - pierces through the dura mater and enters the spinal canal, knocks out a larger portion of the body
What is the lumbar cistern?
Enlargement of the subarachnoid space between the conus medullaris of spinal cord and inferior end of subarachnoid space and dura mater.
What 3 things does the lumbar cistern contain?
1) CSF
2) Filum terminale
3) Cauda equina
Why is the lumbar cistern a good place to administer a lumbar puncture?
Spinal cord is not present here so not at risk of damage
Nerve roots making up the cauda equina are mobile and move out of the way when a lumbar puncture is adminstered so are also not at risk of damage
How does the length of the spinal cord change from foetus to adult and why?
Spinal cord extends the entire length of the spinal column in a foetus at 2-3 months - at this point all segmental spinal nerves are give off at their corresponding vertebral level
As the vertebral column grows at a faster rate than the spinal cord, at birth the spinal cord terminates at around L3 and by adulthood the spinal cord terminates at L1/L2
What is the main blood supply of the spinal cord?
Receives arterial blood mainly via the unpaired anterior and paired posterior spinal arteries which typically arise from the vertebral arteries
The segmental medullary and radicular arteries support the spinal arteries along the length of the cord
Which arteries do the spinal arteries come off in the neck, thoracic, abdominal and pelvic regions?
Neck = vertebral Thorax = Posterior intercostal Abdomen = Lumbar Pelvis = lateral sacral
What is the difference between white and grey matter in the spinal cord?
White matter contains axons
Grey matter contains cell bodies
We have a dorsal, a ventral and a lateral grey horn, each contains what kind of nuclei?
Dorsal grey horn = sensory
Ventral grey horn = somatic motor
Lateral grey horn = autonomic
At what levels can a lateral grey horn be seen in a cross section of the spinal cord?
(T1-L2) = sympathetic (S2-S4) = parasympathetic
What kind of fibres travel in the dorsal root?
Sensory
What kind of fibres travel in the ventral root?
Somatic motor and visceral motor
What happens to the amount of white matter as you ascend the spinal cord?
The amount of white matter increases as you ascend the spinal cord
How does the size of the ventral grey horn change as you move along the cord?
Ventral grey horn is enlarged where motor fibres to the limbs arise
At the cervical (Upper limb) and lumbosacral (lower limb) enlargements
Above which spinal cord segment can 2 dorsal columns be seen on each side of the midline and what are they called?
Above T6
Gracile fascicle medially and cuneate fascicle laterally
What kind of sensory info is carried in the cuneate and gracile fascicle?
Sensory info from the lower limb is carried in the gracile fascicle and sensory info from the upper limb is carried in the cuneate fascicle, so the cuneate fascicle only arises at the level at which sensory info from the upper limb reaches the spinal cord
What is meant by the statement that ‘the spinal grey matter is regionally specilised’?
The grey matter is divided into regions called laminae
These are the sights of sensory or motor nuclei
They each extend a varying length of the cord
Certain functions in the body relate to certain laminae
Name 4 major ascending and descending fibre tracts?
1) Dorsal column
2) Lateral corticospinal tract
3) Ventral corticospinal tract
4) Spinothalamic tract
What info is carried in the dorsal columns?
Joint position sense and vibration sense
What info carried in the lateral and ventral corticospinal tracts?
Voluntary movement
What info is carried in the spinothalamic tract?
Pain, light, touch and temperature sense
Do the dorsal columns carry info from the contralateral or ipsilateral side?
Ipsilateral
What is meant by ipsilateral?
Same side
Do the lateral corticospinal tracts carry info to the contralateral or ipsilateral sides?
Ipsilateral
Do the ventral corticospinal tracts carry info to the contralateral or ipsilateral sides?
Contralateral
Do the spinothalamic tracts carry info from the contralateral or ipsilateral sides?
Contralateral
