Spinal Cord and Meninges Flashcards
Describe the spinal cord
Part of the central nervous system
Within the vertebral canal
Covered with 3 layers of meninges
List the boundaries of the vertebral canal
Body of vertebra
Pedicle
Lamina
Spinous process
Transverse process
Vertebral foramen
Describe the development of the spinal cord
The vertebral column grows faster than the spinal cord.
In the embryo (8 weeks), the spinal cord and vertebral canal are equivalent lengths. [spinal segments = vertebrae]
In neonates, the spinal cord ends at the L3 vertebra.
In adults, the spinal cord extends from the foramen magnum to the disc between L1/L2
Define the extent of the spinal cord within the vertebral canal
Begins at the foramen magnum of the skull, as a continuation of medulla oblongata.
Ends at L1/L2 vertebrae in adults.
Inferior end of the cord is called the conus medullaris which narrows as filum terminale.
External features of the spinal cord
Cervical enlargement between C4-T1 vertebrae
(brachial plexus)
Lumbosacral enlargement between T11-S1 vertebrae
(lumbosacral plexus)
Internal features of the spinal cord
Contains gray matter and white matter
Gray matter - inside : looks like a butterfly
White matter - outside : covers the gray matter
Describe the gray matter of the spinal cord
Contains neuronal cell bodies within its ‘horns’
Has a central canal
Anterior and posterior grey commissures.
Describe the horns of the gray matter in the spinal cord
TOP
MIDDLE
STUBBY BOTTOM
- Dorsal (posterior) horns : inter-neurons
- Lateral horns : visceral (autonomic) motor neurons
- Ventral (anterior) horns : somatic motor neurons
Describe the white matter of the spinal cord
Columns containing a number of ascending and descending tracts.
All tracts are paired and most decussate.
Anterior and posterior white commissures.
Describe the 3 parts of white matter
Ventral (anterior) columns
Lateral columns
Dorsal (posterior) columns
Describe the structure of the spinal cord
The spinal cord is ‘divided’ into segments that are associated with one pair of spinal nerves.
Cervical - 8 segments and nerves
Thoracic - 12
Lumbar - 5
Sacral - 5
Coccygeal - 1
Spinal nerve terminology
Rootlets converge to become roots
Ventral (motor, efferent) and dorsal (sensory, afferent) roots converge to become a spinal nerve (mixed motor and sensory)
Spinal nerves divide into ventral and dorsal rami (mixed motor and sensory nerve fibres)
Spinal nerve
Mixed motor and sensory nerves
Formed by the converging of ventral and dorsal roots.
Rami
Mixed, motor and sensory nerve fibres.
Formed by the division of spinal nerves
C1 nerve
Passes between the occipital bone and the atlas.
C8 nerve
Passes between C7 and T1
Describe the relationship between the number of vertebrae and spinal nerves.
Seven cervical vertebrae – Eight cervical spinal nerves
1-4 coccygeal vertebrae – One coccygeal spinal nerve
Number of vertebrae and spinal nerves are equal in other regions.
31 pairs of spinal nerves emerge from the intervertebral foramina, each nerve through its own foramen (except C1).