Spinal Cord + Meninges Flashcards
Where does spinal cord begin?
Foramen magnum of skull
Continuation of medulla oblongata
Where does spinal cord end?
L1/L2 vertebrae
What’s on inferior end of spinal cord?
Conus medullaris - narrows as film terminale
Where’s cervical enlargement?
Between C4-T1 (brachial plexus)
Where’s lumbosacral enlargement?
Between T11-S1 (lumbosacral plexus)
Length of spinal cord and vertebrae in embryo (8 weeks)?
Equivalent lengths
Spinal segments = vertebrae
Where does spinal cord end in neonates?
L3 vertebra
Growth of spinal cord:
Vertebral column grows faster than spinal cord
External features on spinal cord:
Cervical and lumbosacral enlargements
Conus medullaris
Posterior median sulcus
Anterior median fissure
What areas are involved in innervation of limbs?
Cervical and lumbosacral enlargements
What is the end of spinal cord called?
Conus medullaris
What does grey matter contain?
Neuronal cell bodies within ‘horns’
Lateral horns:
Contain visceral (autonomic) motor neurons
Ventral horns:
Contain somatic motor neurons
Dorsal horns:
Contain interneurons
What does white matter contain?
Columns - contain a number of ascending and descending tracts
What are tracts like in white matter?
All tracts are paired and most decussate
Where do spinal nerves emerge from?
Intervertebral foramina
How many pairs of spinal nerves emerge from intervertebral foramina?
31
What does each nerve relate to?
A spinal segment
How many vertebrae are there?
Cervical = 7
Thoracic = 12
Lumbar = 5
Sacral = 5
Coccygeal = 4
How many spinal nerves are there?
Cervical = 8
Thoracic = 12
Lumbar = 5
Sacral = 5
Coccygeal = 1
What’s the spinal cord divided into?
Segments that are associated with one pair of spinal nerves
What’s the structure called at the roots of lumbar and lower spinal nerves?
Caudate equina
What are cervical spinal nerves numbered according to?
Vertebra below C1-C7 and C8 (exception)
There are 7 cervical vertebrae and 8 cervical spinal nerves
What are all other spinal nerves numbered according to?
Vertebra above…
T1-T12
L1-L5
S1-S5
Co1
Where does C1 spinal nerve emerge from?
Between occipital bone of skull and C1 (atlas)
Where do all spinal nerves emerge from except C1?
Adjacent vertebrae
How are spinal nerves formed?
Rootless converge to become roots
Ventral and dorsal roots converge to become a spinal nerve
What’s in ventral root?
Motor nerve fibres - efferent
What’s in dorsal root?
Sensory nerve fibres - afferent
What’s in spinal nerve?
Motor and sensory nerve fibres
What do spinal nerves divide into?
Ventral and dorsal rami
What’s in ventral and dorsal rami?
Motor and sensory nerve fibres
How do lumbar nerves exit canal?
Must travel down vertebral canal to their own intervertebral foramen
What does the lower third of vertebral canal contain?
Roots of spinal nerves of L2 and lower
Filum terminale
How are lower spinal segments laid in cauda equina?
Adjacent to vertebrae above their own level
e.g. L1 segment adjacent to T11
What does the meninges consist of?
Three membrane that surround, protect and suspend the brain, spinal cord and spinal nerves
What is the dura mater?
Outermost layer
Thick + protective
2 layers of dura mater:
Outer periosteal
Inner meningeal
What is dura mater attached to?
Inner surface of cranium
What is dura mater called as it descends through vertebral canal?
Dura sac - not attached to bone
Where does dura mater narrow?
At lower border of S2 vertebra
Fuses with filum terminale
WhereWhen does dura cover roots of spinal nerves?
As they pass through intervertebral foramina
What is arachnoid mater?
Delicate
Avascular layer
Position of arachnoid mater:
Deep to dura
Lines dura sac - no space between layers
How does arachnoid mater connect to pia mater?
Arachnoid trabeculae - like a bridge
What does arachnoid mater enclose?
Subarachnoid space - between arachnoid and pia mater
Where does subarachnoid space end?
Border of S2 vertebra
What does subarachnoid space contain?
CSF
Blood vessels supported by web-like fibres
What does subarachnoid space enclose?
Caudal equina (as lumbar cistern)
What is pia mater?
Innermost layer
Thin and vascular
Position of pia mater:
Adhered to surface of brain + spinal cord
Covers surface of spinal roots
What does pia mater become at inferior end of cord?
Filum terminale - attached to coccyx
What is pia mater like in vertebral canal?
Triangular extensions that are laterally attached to arachnoid mater in dural sac
Suspend the spinal cord
What are triangular extensions of pia also called?
Denticulate ligaments
What’s in epidural space?
Fatty matrix
Internal vertebral venous plexus
Where does epidural space run from?
Foramen magnum to sacral hiatus
What is epidural space internal to?
Periosteum
What is epidural space also called?
Extra dural space
How many directions of blood supply is there to spinal cord?
2
What are the two directions of blood supply in spinal cord?
3 longitudinal arteries
Numerous segmental arteries
Where are the 3 longitudinal arteries found?
Branches of subclavian artery
Lie on surface of cord
Where are the numerous segmental arteries found?
Branches of aorta
How do the numerous segmental arteries enter vertebral canal?
Via intervertebral foramina
Arteries in longitudinal blood supply:
2 posterior spinal arteries
1 anterior spinal artery
Where do the 2 posterior spinal arteries arise from?
Vertebral and posterior inferior cerebellar arteries
Where does the 1 anterior spinal artery arise from?
Vertebral arteries
What reinforces segmental supply?
Segmental / radicular branches
Where do segmental arteries enter?
Via intervertebral foramina
What are some of the segmental arteries?
Cervical, thoracic and lumbar
Where do cervical segmental arteries arise from?
Vertebral arteries
Where do thoracic segmental arteries arise from?
Intercostal arteries
Where do lumbar segmental arteries arise from?
Lumbar arteries
What structures are involved in venous drainage?
Longitudinal channels on surface of cord
Internal vertebral venous plexus
External vertebral venous plexus
Structure of longitudinal channels on surface of cord?
No valves
Where does blood flow in longitudinal channels on surface of cord?
Slowly in either direction
Where does internal vertebral venous plexus lie?
In extradural fat of epidural space
What does external vertebral venous plexus drain?
Medullary cavity of vertebral bodies
What does external vertebral venous plexus connect to?
Connects to segmental veins
Give examples of segmental veins:
Lumbar and azygous veins
What doe venous connections allow?
Metastatic spread of tumours
What layers does lumbar puncture go through?
Skin
Superficial fascia
Supraspinous ligament
Interspinous ligament
Ligamentum flavum
Extradural (epidural) space
Dura mater
Arachnoid mater
Subarachnoid space
Where is a lumbar puncture performed?
Between L3/L4 or L4/L5
