Spinal Cord & Meninges Flashcards
What are the contents of the vertebral canal?
\+ Spinal cord \+ Meninges \+ Spinal roots (that form spinal nerves) \+ Extradural space and fat \+ Blood vessels
What are the vertebral boundaries of the vertebral canal?
Transverse process Superior & inferior articular facet Vertebral foramen Pedicle (L) Intervertebral foramen (L) Vertebral body (A) Intervertebral disc (A) Zygopophysial (facet) joint (P) Spinous process (P) Lamina (P)
What are the ligamental boundaries of the vertebral canal?
Supraspinous ligament
Intraspinous ligament
Ligamentum flavum
Posterior longitudinal ligament
Where does the spinal cord begin?
Begins at the foramen magnum as a continuation of the medulla oblongata
Where does the spinal cord end?
At L1/L2 vertebrae in adults (42-45cm long)
What are the names for the inferior end of the spinal cord?
Conus medullaris which narrows as filum terminale
Where is cervical enlargement?
Between C4-T1 (brachial plexus)
Where is lumbosacral enlargement?
Between T11-S1 (lumbosacral plexus)
Describe spinal cord development
+ In the embryo (8wks), the spinal cord and vertebral canal are equivalent lengths
+ In neonates, the spinal cord ends at L3 vertebra
+ Vertebral column grows faster than spinal cord
What are features of the grey matter within the spinal cord?
Form H-shaped structure, contains neuronal cell bodies within the ‘horns’
What type of neurons does each horn contain?
Lateral - visceral/autonomic motor neurons
Ventral/anterior - somatic motor neutrons
Dorsal/posterior - interneurons
What are features of the white matter within the spinal cord?
Forms columns containing a number of ascending and descending tracts - all are paired and most are decussate
What are other landmarks of the spinal cord (transverse/cross section)?
+ Posterior/dorsal median fissure
+ Anterior median fissure
+ Anterior white commissure
+ Central canal
What are the components/features of the PNS spinal nerves and ganglia?
31 pairs of nerves (mixed, union of dorsal and ventral roots)
Spinal ganglion (dorsal root ganglia)
Dorsal rami
Ventral rami
Rami communicantes
Sympathetic ganglion
Where do the 31 pairs of spinal nerves emerge from?
Intervertebral foramina - each nerve exits through a specific one
Each nerve relates to a spinal segment
What is the result of the vertebral column growing faster than the spinal cord?
Cauda equina (horse’s tail) is formed:
+ Lumbar nerves must travel down the vertebral canal to their own intervertebral foramen to exit the canal, as the lower spinal segments of the cord lie adjacent to vertebrae ABOVE their own level
+ Lower third of VC contains roots of spinal nerves of L2 and lower, as well as filum terminale
What is special about the numbering of cervical nerves?
They are numbered according to the vertebra BELOW them (C1-C8)
There are 7 cervical vertebrae and 8 cervical nerves
What are the layers of the meninges?
Dura Mater
Arachnoid Mater
Pia Mater
What are features of the dura mater?
+ Outermost; thick protective layer consisting of 2 layers (outer periosteum; inner meningeal layer)
+ Attached to inner surface of cranium. As it descends through the canal: dural sac
+ Narrows extensively at lower border of S2 where it fuses with filum terminale at coccyx
+ Dura covers roots of the spinal nerves as they pass through the intervertebral formina
What are features of the arachnoid mater?
+ Delicate, avascular layer which lies deep to dura; no space between layers
+ Connects to pia via arachnoid trabeculae
+ Encloses subarachnoid space:
- continuous with space around brain
- ends at lower border of S2
- contains blood vessels supported by spider-like fibres
- encloses the cauda equina (as lumbar cistern)
What are features of the pia mater?
+ Innermost; thin vascular layer closely adhered to the surface of brain and spinal cord, also covers surface of spinal roots
+ Becomes the filum terminale at inferior end of cord, attached to coccyx
+ In the VC, the triangular extensions of pia (denticulate ligaments) are laterally attached to the arachnoid mater in the dural sac and suspend the cord in space
What are the features of the extradural space?
+ Fatty matrix
+ Runs from foramen magnum to sacral hiatus
+ Internal to periosteum
+ Contains internal vertebral venous plexus
What are the two sets of arteries that form the spinal cord blood supply?
+ Longitudinal arteries (3)
- branches of subclavian artery
- lie on surface of the cord
+ Numerous segmental arteries
- branches of the aorta
- enter VC via intervertebral foramina
What are the features of the longitudinal arteries?
+ Forms:
- posterior spinal arteries (2)
- anterior spinal artery (in ant. median fissure); gives off sulcal arteries
+ Vertebral arteries ascend in the neck via the foramen transversaria of cervical vertebrae. They give branches at the foramen magnum
What are features of the segmental/radicular arteries?
Branches from aorta enter via the intervertebral foramina:
- Cervical (arise from vertebral arteries)
- Thoracic (arise from intercostal arteries)
- Lumbar (arise from lumbar arteries)
What are the features of venous drainage of the spinal cord?
+ Longitudinal channels on surface of cord
- no valves, blood flows slowly in either direction
+ Internal vertebral venous plexus
- lies in extradural fat of
epidural space
+ External vertebral venous plexus
- drains medullary cavity of vertebral bodies and connects to segmental veins (e.g lumbar and azygos veins)
What is the potential problem created by venous connections?
They allow metastatic spread of tumours (e.g breast and prostate cancer can be spread to vertebral bodies as bony metastases)
What structures does the needle pass through during a lumbar puncture?
- Skin
- SC fascia and fat
- Supraspinous ligament
- Interspinous ligament
- Ligamentum flavum
- Epidural space and extradural fat
- Dura mater
- Arachnoid mater
