Session 5 - The vertebral column Flashcards
How are the vertebra held together?
-By ligaments
How many bones are in the vertebral column? How are these organised?
-33 bones; 24 discrete single vertebrae; 9 fused vertebrae
What are the gross functions of the vertebral column?
- Centre of gravity
- Attachments for bones of appendicular skeleton
- Attachment for trunk muscles
- Protection and passage of spinal cord
- Segmental innervation
What are possible movements of the vertebral column?
- Flexion
- Extension
- ABduction
- ADduction
- Rotation
How does the vertebral column act as the centre of gravity?
-The weight of the body is projected into the lower limbs about an imaginary line that passes centrally through the natural curvatures of the vertebral column
What bones does the vertebral column act as a site of attachment for?
- Skull
- Ribs (indirectly the upper limb)
- Hip bones (indirectly lower limb)
How is an upright posture maintained?
-Continuous low level contraction of trunk muscles to support the body weight
How does the vertebral column protect the spinal cord?
-Spinal cord runs through the spinal canal formed by successive vertebral foramen for its entirety
Describe the presentation of the vertebral column in the fetus
- A single flexed curvature which faces anteriorly (concave anteriorly)
- Known as primary curvature
-Where is the primary curvature maintained in the vertebral column thoughout life?
-Thoracic and sacral/coccygeal spine
What is kyphosis?
-An exaggerated anterior curvature
What is lordosis?
-An exaggerated posterior curvature
What is scoliosis?
-Lateral deviation of the backbone
Describe the presentation of the vertebral column in the young adult
-4 distinct curvatures arranged to give a sinusoidal shape
2 anterior curvatures (thoracic and sacral)
2 Posterior curvatures (cervical and lumbar)
What are posterior curvatures of the vertebral column also known as?
-Secondary curvatures
What characteristic does the sinusoidal profile of the vertebral column provide?
-Great resilience
How does the vertebral column change from that in a foetus to that of a young adult?
- Primary curvature becomes remodelled as the baby lifts the head, the primary curvature is replaced by a posterior curvature (cervical region)
- The lumbar spine is then remodelled during crawling and walking to form the second posterior concavity
Where are naturally weak points of the spine?
-C7/T1
-T12/L1
-L1/S5
Points of change in curvature
Describe the presentation of the vertebral column in old age
-Secondary curvatures start to disappear with the vertebral column seeming to return to its original shape in the foetus and a fully continuous primary curvature re-establishes
Name the fused vertebrae
- Sacrum (5)
- Coccyx (4)
Name the discrete vertebrae
- Cervical (7)
- Thoracic (12)
- Lumbar (5)
Which vertebrae are capable of individual movement?
-Discrete vertebrae
What are the two segments of discrete vertebrae?
- Anterior vertebral body
- Posterior vertebral arch
What part of the discrete vertebrae is the main weight-bearing?
-Vertebral body
How are adjacent vertebrae linked together?
-Through intervertebral discs which interdigitate with the vertebral body from C2/C3 to L5/S1 joints
What cartilage lines the vertebral body?
-Hyaline
How does the size of the vertebrae change throughout the discrete vertebrae?
-Increases from top-downwards
What three processes emerge from a vertebral arch?
- Two transverse processes laying laterally on either side of midline
- One spinous process at the posterior midline
What is the pedicle of the neural arch?
-The part of the neural arch between the vertebral body and the transverse process
What is the lamina of the neural arch?
-The part of the neural arch between the transverse and spinous processes
What are facets of the neural arch?
-Cartilage-lined articular processes which lie superiorly and inferiorly at the junction between the pedicle and the lamina
What do facets forms
-Synovial joints between successive vertebrae
What strengthens the facet joints between successive vertebrae?
-Ligamentum Flavum
What do facet joints prevent?
-Anterior displacement of vertebrae
Are facet joints weight bearing?
-Yes when upright
Where are the vertebral notches on the neural arch?
- One superior on pedicles
- One inferior on pedicles
What forms the interverebral foreman?
-Inferior vertebral notch of one vertebrae with the superior vertebra notch on the successive vertebrae on each side of the vertebral column
What passes through the intervertebral foreman?
-Segmental nerves from the spinal cord
What is an intervertebral disk?
-A disc of cartinaginous tissue which separates successive vertebrae between levels C2/C3 to L5/S1
Why are intervertebral discs called symphysis?
-They form secondary cartilaginous joints which do not ossify
What is responsible for the high flexibility of the vertebral column?
-The intervertebral disks
What are the functions of intervertbral disks?
- Join successive verterbrae
- Provide flexibility
- Act as a shock absorber (dampens impact to skull)
Are IVD all the same size?
-No, size increases inferiorly
Describe the morphology od the intervertebral disks in the thoracic and lumbar regions
-Wedge shaped with the thickest section anteriorly and the thinnest section posteriorly
Why is it important that the intervertebral disks are wedge-shaped in the thoracic and lumbar regions?
-Accounts for the secondary curvatures of the spine
What forms the bulk and turgidity of the IVD?
-Its high water content
What are the two regions of an IVD?
- Central nucleus pulposus
- Peripheral annulus fibrosus
What makes the annulus fibrosus?
- A series of annular bands arranged in various orientations
- The outerbands are collagenous
- The inner bands are fibrocartilaginous
What characteristics does the annulus fibrosus have?
- Very resilient
- Stronger then vertebral body
- Shock absorber
What is the nucleus pulposus?
-Centre of an IVD which is the jelly-like remnant of the notochord
Which section of an IVD holds its high water content?
-Nucleus pulposus -> acts as a water reservoir
Why can the size of the nucleus pulposus change throughout the day?
-Depending on water distribution within the IVD
What is the difference in the position of the nucleus pulposus in infants and adults?
- Central in infants
- Found more posteriorly in adults
What most common possible consequence of degeneration of nucleus pulposus?
- The nucleus pulposus can herniate through annuar fibrosus
- Known as slipped disk (most commonly posterio-laterally)
When can a slipped disk cause paralysis?
-When the nucleus pulposus herniates posteriorly into the spinal cord
Why can degeneration of nucleus pulposus occur with age?
-The nucleus can dehydrate
What is marginal osteophytosis and when can it occur in IVD?
- Projections of bone which occurs at sites of cartilage degeneration
- Occurs when nucleus pulposus degenerates, reducing the height of the IVD
- This changes the load stresses on the IVD leading to reactive marginal osteophytosis
Why can nucleus pulposus degeneration lead to osteoarthritis?
-As the IVD height decreases, increased stress is placed on the facet joints which can lead to osteoarthritis at the same level
How can nucleus pulposus degeneration lead to compression of spinal nerves?
-Decrease in IVD height decreases the size of the intervertebral foramen which can lead to congestion and compression of the segmental nerves
What is the result of degeneration of the annulus fibrosus?
-Marginal osteophytosis -> height of disc space largely preserved
What is spondylosis?
- Spinal condition resulting from degeneration and flattening of the IVD in the cervical, thoracic or lumbar regions. There is a narrowing of the space occupied by the disk and osteophytes present
- Symptoms include pain and restriction of movement
What main ligaments straps together sucessive vertebrae and IVDs?
-Anterior longitudial ligament and posterior longitudial ligaments which run up the anterior and posterior longitudial axis of the vertebral column, respectively
Which of the longitudial ligaments are shorter?
-Anterior longitudial ligament
Which of the longitudial ligaments are stonger?
-Anterior lingitudial ligament
Describe the course of the anterior longitudial ligament, including its morphology and attachments
- A flat band which broadens as it passes downwards
- Extends from atlas to the upper sacrum
- Attaches to periosteum of vertebral bodies but free over IVDs
Describe the course of the posterior longitudial ligament, including its morphology and attachments
- Extends posterior to vertebral body from axis to the canal of the sacrum
- Narrows as it passes downwards
- Serrated margins, largest over IVD
- Attached to IVD but free from vertebral bodies
What separates the posterior longitudial ligament and the vertebral bodies?
-Basivertebral veins
What three ligaments are associated with the neural arch?
- Ligamentum Flavum
- Interspinous ligament
- Supraspinous ligament
Describe ligamentum flavum
- High content of elastic fibres
- Join the laminae of succesive verebrae
- Attached to the front of the upper lamina and back of the lower lamina
- Stretched by flexion of the spine
- Re-enforce synovial facets
Describe supraspinous ligament
- Joins the tips of spinous processes
- Strong fibrous tissue
- Lax in the extended spine
- Draw taut in the flexed spine
Describe interspinous ligament
- Relatively weak sheets of fibrous tissue
- Units spinous processes along their superior and inferior border
- Well-developed only in lumbar spine
- fuse with supraspinous ligament
What is the posterior longitudial legament, when continued above axis?
-Membrane tectoria
What is ligament nuchae?
- A ligament which maintains the secondary curvature of the cervical spine , helping the cervical spine to support the head
- Major site of attachment for neck and trunk muscles
Where is the ligament nuchae?
-From Occiput to thoracic spinal ligaments
What are continuations of ligament nuchae?
-Interspinous and supraspinous ligaments
What is occiput?
-Occipital protuberance (back of skull)
How do fused vertebrae differ morphologically from discrete vertebrae?
- No IVD
- No vertebral foramen
- Coccyx has no interverebral foramen
- Sacrum has modified intervertebral foramen
Describe distinguishable features of the cervical vertebrae
- Smallest of discrete vertebrae
- Has a bifid spinous process
- Has an oval transverse foramen in the wide transverse process (foramen transversum)
- Large triangular vertebral foramen
What passes through the foramen transversum of cervical vertebrae?
-Vertebral artery
How does C7 differ from the rest of the cervical vertebrae?
- Foramen transversum passes accessory vertebral veins
- Spinous process is not bifid
Describe distinguishable features of the thoracic vertebrae
- Intermediate in size which increases downwards
- Vertebral foramen small and circular
- Demi-facets on side of vertebral body for articulation with head of rib
- Has costal facets on transverse processes for articulation with tubercle of rib (except T11 and T12)
Describe the distinguishable features of lumbar vertebrae
- Largest of discrete vertebrae
- Lack costal facets and demifacets
- Vertebral foramen is triangular and small
What are atlas and axis?
-C1 and C2, respectively
Why are atlas and axis atypical vertebrae?
-They are structurally and functionally different
What are the articulations of atlas?
- Skull above (atlanto-occipital joint)
- Axis below (atlanto-axial joint)
How does atlas structurally differ from other vertebrae?
- No strict vertebral body
- No spinous process
- Widest cervical vertebrae
Which is the strongest cervical vertebrae?
-Axis
How is axis distinguishable from other vertebrae?
- Has the dens
- Rugged lateral masses
- Large spinous process
What is the function of the dens?
-Fuses with atlas to prevent horizontal displacement
Which vertebrae is broken in hangmans fracture?
-Axis
What types of injury is the cervical spine prone to?
- Whiplash in RTA
- Sports injuries
What injury is the lumbar spine susceptible to?
-Herniation of L4/L5 or L5/S1
How long is the vertebral column?
-around 70-75cm (42% of the height)
