Flashcards in Session 8 The Vertebral Column Deck (41)
Describe the Vertebral Column
Forms the main central axis of the skeleton and forms the skeleton of the neck.
Around 70-75cm long.
Accounts for 42% of height (average UK height 165-175cm).
Made from a series of small bones joined and close to each other.
24 Discrete Vertebrae - all separable and capable of individual movement
9 Fused vertebrae - to give 2 innominate structures (sacrum - fusion of 5 fierce fad, coccyx - fusion of 4 vertebrae)
What are the Gross Functions of the Vertebral Column?
Centre of gravity of the body: weight of the body is projected into lower limbs about a line that passes centrally through the natural curvatures of the vertebral column
Attachments for Bones: both appendicular and axial skeleton. Together with the hip bones, they bear most of the body weight.
Attachments for Trunk muscles: --> upright posture is determined by continuous low level contraction of trunk muscles to support body weight
Protection and Passage of the Spinal Cord:
Segmental Innervation of the body: (allowing segmental nerves to leave or join the cord at specified points along the continuum of the vertebral column to supply their targets).
What are the movements of the vertebral column?
Lateral flexion (abduction of the vertebral column)
Flexion (I.e. Bowing)
Describe the Vertebral Column in the Foetus
Lies flexed in a single curvature throughout its extent
Curvature faces anteriorly - concave anteriorly (or an anterior flexion)"
Known as the primary curvature
The primary curvature is regained throughout life in the thoracic, sacral and coccygeal parts.
Describe the Vertebral Column in the Young Adult
(Viewed from the side): 4 distinct curvatures - approximate S figure.
Sinusoids profile - sinuous bends give the column resilience.
2 anterior flexions (anterior concavities)
2 posterior flex ions (posterior concavities).
Anterior concavities are continuations of the primary curvature of the foetus.
Posterior concavities are secondary curvatures.
Describe the development of the Secondary Curvatures
During development from the fetus to young adult, the primary concave curvature is remodelled in parts - the C-shaped column opens up to elongate.
The cervical spine develops the first posterior concavity when a young child begins to lift its head. This becomes the first secondary curvature.
The lumbar spine also opens during crawling until the child begins to stand up and walk. A second posterior concavity then appears and becomes the second secondary curvature.
Describe the Vertebral Column in old age
The secondary curvatures start to disappear.
The vertebral column seems to return to its original shape in the foetus - a fully continuous primary curvature is re-established.
The vertebral column closes up again (as if in the foetus)
Describe the structure of a typical vertebra
Consists of a vertebral body (anteriorly) and a vertebral arch/neural arch (posteriorly). Between them they enclose the spinal canal/vertebral foramen/neural foramen.
Describe the Vertebral Body
Usually the largest part of the vertebra and the main weight-bearing part.
Also the main site of contact between adjacent vertebrae (apart from 2 atypical bones).
Lined with hyaline cartilage.
Linked to adjacent vertebral bodies by way of intervertebral discs.
Size of body of vertebrae increases top-downwards.
Vertebral bodies and intervertebral discs inter-digitate sequentially from C2/C3 - L5/S1 intervertebral joints.
Describe the Vertebral/Neural Arch
3 processes emerge from vertebral arch.
Spinous Process (n=1) - midline, posterior
Transverse Process (n=20) - found laterally, 1 on each side of midline.
The pedicle is the part of the neural arch between the vertebral body and the transverse process.
The lamina is the part of the neural arch between the transverse process and the spinous process.
Describe the articular processes of the neural arch
At the junction of the lamina and the pedicle are articular facets,
1 above and 1 below on each side. (N=2)
They are found on both sides (total n=4)
They are hyaline cartilage-lined
Allow for synovial joints to be formed between neural arches of adjacent vertebrae.
They are strengthened by ligamentum flavour.
The joints formed between adjacent neural arches are synovial and prevente anterior displacement of the vertebrae. They allow for limited movements and can bear weight when uprighting.
Describe the elaborations of the Vertebral/Neural Arch
Each pedicle has 2 notches that reduce its height called vertebral notches. (Superior and inferior).
Superior and inferior vertebral notches on each side of adjacent vertebrae form an intervertebral foramen which segmental nerves pass from cord to periphery through. The dorsal root ganglia is found here.
Describe the Intervertebral Discs
Forms the joint between vertebral Jodie's.
Secondary cartilaginous joints hence known as symphoses.
Presence is responsible for the flexibility of the vertebral column.
Acts as a shock absorber, dampening impact shocks to the skull.
Not all the same size - increase in size from superior to inferior.
Wedge-shaped in lumbar and thoracic levels; thickest anteriorly and thinnest posteriorly in the lumbar and thoracic levels.
Wedge-shaped of the IVD accounts for secondary curvature of the spine.
High water content that keeps it turgid and forms its bulk. May shrink in size with age. This shrinkage may account for reduction in height with age (accept with caution).
Consists of 2 regions - a central region and a peripheral region.
The discs permit tilting movements between adjacent vertebrae.
Describe the Peripheral Region of the Intervertebral Disc
The annulus fibrosis has a highly complex design, made from a series of annular bands with varying orientations.
Outer bands are collagenous and inner bands are fibro-cartilaginous,
Very resilient and stronger than the vertebral body.
It is the real shock absorber.
It is attached to the cartilaginous plates covering the bodies of the vertebrae.
Describe the Central Region of the Intervertebral Disc
The nucleus pulposus is jelly-like, mucoid and has high osmotic pressure - acts as a water reservoir for the disc.
Changes in size and thickness throughout the day depending on water distribution within the disc. Also changes in size with age and is surrounded entirely by annulus fibrosus.
Centrally located in the infant but can be found posteriorly in the adult.
Describe the Degeneragion of Nucleus Pulposus
It can dehydrate with age - height of the IV dis then decreases.
When this happens, load stresses on the IV disc alter, leading to reactive marginal osteophytosis (outgrowth of bone tissue) adjacent to the affected end plates.
As the disc space decreases in height, increased stress is also placed on the facet joints. This can lead to osteoarthritis on the facet joints - can lead to osteoarthritis of the facets at the same level.
Decreasing disc height can also lead to congestion in the intervertebral foramen and compression of segmental nerves.
Describe Degenerative Annular Disease
Degeneration of the annulus fibrosus leads to marginal osteophytosis at the endplates.
Progressive Degeneragion of the annulus leads to increasing osteophytosis at tithe disc space margins - then height of disc space is largely preserved,
Usually seen in thoracolumbar spine of persons over 50 years of age.
In literature, this entity had been termed "spondylosis deformans" or "senile ankylosis" with increasing age.
Does degenerative disc disease actually refer to?
Umbrella term is often used to refer to degeneration of one or both components of the discs - in practice, degeneration annulus and the nucleus pulposus occur concurrently. It usually doesn't make a lot of difference to the referring clinician which component of the disc has degenerated.
What is a Herniated Intervertebral Disc?
The nucleus pulposus can herniate through annulus fibrosus if there is degeneration. Occurs most commonly posterolaterally.
Results in compression of spinal segmental nerves (pain).
Posterior herniation may compress the spinal cord (leading to complete paralysis).
What are the two major ligaments which run along the longitudinal axis of the vertebral column?
All vertebra and intervertebral discs are strapped together by two major ligaments which run along the longitudinal axis of the vertebral column.
One occurs anteriorly to the vertebral column and is known as the Anterior Longitudinal Ligament.
The other occurs posteriorly and is known as the Posterior Longitudinal Ligament.
NB: there are other additional ligaments that support the integrity of the vertebral column but these will be considered in detail only in Phase II.
Describe the Anterior Longitudinal Ligament
Much stronger than Posterior equivalent,
Prevents excessive extension of the vertebral column. (Excessive flexion is prevented by all of the other ligaments).
Flat band that broadens as it passes downward.
Extends from anterior tubercle of the atlas to the front of the upper part of the sacrum, firmly united to the periosteum of the vertebral bodies. It is free over the intervertebral discs.
Describe the Posterior Longitudinal Ligament
Extends from the back of the vertebral body of the axis to the canal of the sacrum,
It is continued above the body of the axis as the membrane tectoria.
Gradually narrows as it passes downwards.
It has serrated margins.
The serrations are broader over the intervertebral discs to which they are firmly unitedl
The ligament narrows over vertebral bodies. The ligament is separated from the vertebral bodies by the emerging basivertebral veins.
What is the Ligamentum Flava of the Vertebral Ligament?
Yellow in colour due to high content of elastic fibres.
They join laminae of adjacent vertebrae and are attached to the front of the upper lamina and to the back of the lower lamina.
They are stretched by flexion of the spine (leaning forwards).
What is the Supraspinous Ligament?
Joins the tips of adjacent spinous processes.
They are string bands of white fibrous tissue.
They are lax in the extended spine.
Full flexion effectively prevents erector spinal muscles from extending the spine so during flexion of the vertebral column, the Supraspinous ligament is drawn taut to mechanically support the vertebral column.
What is the Interspinous Ligament?
Relatively weak sheets of fibrous tissue.
They unite spinous processes along their adjacent borders.
They are well-developed only in the lumbar region.
They fuse with Supraspinous ligaments.
What is the Ligament Nuchae/Nuchal Ligament?
Proximal attachment - occipital protuberance at the back of skull
Distal attachment: thoracic spinal ligaments - Interspinous and Supraspinous.
Intermediate attachments - spinal processes of all cervical vertebrae.
Functions: maintains the secondary curvature of the cervical spine, helps the cervical spine support the head, acts as as a major site of attachment of head and trunk muscles e.g. Trapezius
What are the distinguishing, morphological features of Cervical Vertebrae?
Smallest of the discrete vertebrae
Bifid spinous process.
Oval transverse foramen in the transverse process.
Vertebral artery passes through all the cervical foramen apart for C7.
The smaller accessory vertebral veins go through the C7 foramen.
Large vertebral (or neural) foramen.
Broken neck may be sub-clinical (asymptomatic?) because of the large vertebral foramen.
What are the distinguishing, morphological features of Thoracic Vertebrae?
Intermediate in size, increasing in size from above to downwards.
Facets on the sides of the body - Demi-facets for articulating with hrsc ov fun.
Facets (articular processes) on the transverse processes (except T11 and T12) - Coastal facets for articulations with tubercle of rib.
Vertebral foramen is small and circular.
No transverse foramen.
What are the distinguishing, morphological features of Lumbar Vertebrae?
Their articular processes are approximate to the Sagittal plane and hence permit a large degree of flexion and extension but little rotation.
Largest of the discrete vertebrae.
Lack of foramina on the transverse processes.
Lack coastal facets on the side of the body.
Vertebral foramina are triangular and small.