Gross and cross-sectional anatomy of the spinal cord Flashcards
(41 cards)
What is the function of the spinal cord?
1) Conduction:
- Provides tracts that conduct upwards (afferent, sensory, to the brain) and downwards (efferent, motor, to the muscles), connecting different levels of the trunk with each other and with the brain
2) Reflexes: Serves as the reflex center for all spinal reflexes that are involuntary of the brain
- Axon bundles in the CNS are known as tracts
Where is the location of the spinal cord?
Inside the spinal vertebrae canal, extending from the upper border of the atlas (as a continuation of the medulla oblongata) till the L1 & L2 in adults and the upper border of L3 in children
- The first vertebrae is called the atlas
- Conus medullaris is located where the spinal cord ends (L1-L2)
What is the filum terminale? and what is its function?
It is a strand of connective tissue that attaches the conus medullaris to the first coccygeal vertebrae
- It adheres to the bone stabilizing the spinal cord in place
Describe the spinal cord
- 45cm long
- elongated and cylindrical in shape, having 2 enlargements: (cervical enlargements = muscles of the U.L. “C5-T1” & lumbar enlargement, for muscles of the L.L. “L2-S3”)
- It tapers inferiorly forming the conus medullaris
- Filum terminal extends downwards attaching to the back of the coccyx
What is cauda equina?
It is the bundle of spinal nerves coming from L1-L2 till the coccygeal 1
What is the content of the spinal cord below L1 & L2?
- CSF that also surrounds the whole spinal cord
- Roots of spinal nerve arising from the lower lumbar and sacral segments (cauda equina), as they did not exit through the foramen yet
What is the level of the conus medullaris in regard to the vertebral level?
L1 & L2 IN ADULTS WHILE L3 IN CHILDREN
What are the different segments of the spinal cord?
- It comprises 31 segments
- 31 segments of spinal nerves (each segment is attached by two roots “ventral & dorsal”)
- The dorsal root has a ganglion “collection of nerves/cell bodies”
1) 8 cervical
2) 12 thoracic
3) 5 lumbar
4) 5 sacral
6) 1 coccygeal
- Lumbar + sacral + coccygeal = cauda equina below the conus medullaris
At which location does the spinal nerve exit the vertebrae?
All of the nerves exit below the vertebrae except the cervical nerves they exit from above, giving 8 cervical nerves although there are only 7 vertebrae
Describe the composition of the spinal nerve
- The spinal nerve is made when the dorsal and ventral roots join together, a mix of motor and sensory fibers
- The spinal nerve splits into 2: one that goes to the back of the neck known as dorsal rami and the other one moves to the anterio lateral surface known as ventral rami, communicating rami is connected to the ganglia and to the spinal cord
- Dorsal has sensory fibers “afferent”, while ventral has the motor fibers “efferent”
What is the relative position of the spinal cord segment and vertebral body segment?
1) For the cervical nerves the spinal nerve exits above the vertebrae so you add one for each vertebral segment
2) For the thoracic vertebrae 1-6, you add two
3) For the thoracic vertebrae from 7-9, we add 3 to get the corresponding spinal cord segment
4) For the thoracic vertebrae 10, the spinal cord segment associated with it is L1 and L2
5) For the thoracic vertebrae 11, the spinal cord segment associated with it is L3 and L4
6) For the thoracic vertebrae 12, the spinal cord segment associated with it is L5
7) For the lumbar vertebrae 1, the spinal cord segment associated with it are all sacral and coccygeal segments
What is meant by disc herniation?
a condition during which a nucleus pulposus is displaced from intervertebral space
What are the most common sites for disc herniation?
Cervical and lumbosacral region
What is cauda equina syndrome?
It is a central lumbosacral disc herniation, which is a dysfunction of one or more of the sacral nerve roots S2 and below
What is meant by a disc prolapse?
It is a bulging/protrusion of the disk compressing the spinal nerve at a specific level
What is the difference between a tumor and disc herniation in regards to the nerve root affected?
between L4 and L5 is L5 so in herniated disc nerve L5 is affected but in the case of a tumor to the L4 vertebra the L4 spinal nerve will be affected.
- On the other hand in the thoracic region if a disc herniation occurs the above nerve is affected (if the disk between T4 and T5 is enlarged it compresses on the T4 nerve)
What is the importance of the spinal nerves?
- Diagnosing neurological disorders
- Lesion of one or more nerve roots results in neurological defects (muscle weakness, loss of sensation), this will allow us to localize the causing lesion
What is a dermatome?
An area of the skin innervated by sensory axons (cutaneous branches) of a single spinal nerve
C2 The top part of the head
C3 the top part of the neck anteriorly and posteriorly
C4 middle part of the neck anteriorly and posteriorly
C5 from the clavicle to the lateral part of the upper limb (shoulder)
C6 Lateral part of the forearm (UL) and thumb
C7middle of the hand, second third, and half of fourth finger
C8 half of fourth, fifth finger, and medial part of the forearm
T1 Medial part of the arm
T2 Axilla
T2-12 thorax till the umbilical (below it)
L1-5 anterior and inner surface of lower limbs and part of the lower back
L4 median side of the great toe
L4, 5, S1 foot
S1, 2 L5 posterior and outer surface of lower limbs
S1 Lateral margin of the foot and little toe
S2, 3, 4 perineum
What is a myotome?
All the muscles innervated by the motor neuron of a single spinal nerve
for example, biceps are innervated by C5 & 6
If there’s a lesion in the C5 segment, Which region of the skin will be affected? Which muscles will be affected? Which movements will be affected?
Shoulder, biceps, flexion
What happens to the foramen when the disc degenerates?
It narrows
What are the examples of disc problems?
1) Degenerated disc
2) Bulging disc (compresses spinal nerves)
3) Herniated disc (huge buldge)
4) Thinning disc
5) Disc degenerating with osteophyte formation
What are the coverings of the spinal cord?
- Covered by three layers “meninges”
From out to in they are:
1) Spinal dura matter
2) Spinal arachnoid matter (the sub-arachnoid space contains the cerebrospinal fluid)
3) Spinal pia matter
Describe the dura mater
- It is a tough, fibrous outer layer
- The space between it and the bony wall of the canal is called the epidural space
- The space under it the subdural space
- Inferiorly the dura mater ends at the S2 level
