Session 2: Lumbar Spine and Associated Disorders Flashcards
Where does the vertebral column start and where does it end?
It extends from the skull to the apex of the coccyx.
How much of the length of the vertebral column is derived from the intervertebral discs?
25%.
Where does the other 75% come from?
The sacrum and the vertebrae (vertebral bodies).
How many vertebrae are there?
33 in total.
How many cervical vertebrae are there?
7
How many thoracic vertebrae are there?
12
How many lumbar vertebrae are there?
5
How many sacral vertebrae are there?
5
How many coccygeal vertebrae are there?
4
What is the intervertebral disc between L3 and L4 called?
L3/L4
How do the 24 cervical, thoracic and lumbar vertebrae differ to the 9 sacral and coccygeal?
The C,T,L are single vertebrae.
The S,CX are fused.
The CTL are single vertebrae. Why is this important?
It also them to be capable of individual movement. This means that the upper 24 vertebrae are much more mobile than the lower 9.
How does the cervical and lumbar spine differ to the thoracic spine in movement?
Lumbar and cervical spine are relatively mobile. Thoracic spine is not very mobile.
Why is the thoracic spine not very mobile?
Because it is joined by the ribs to the sternum to form part of the thoracic cage.
How many curvatures does the spine have? Which?
4 in total.
2 primary kyphotic and 2 secondary lordotic.
Explain what kyphotic means. Which parts of the spine are kyphotic?
Kyphotic means it is anteriorly concave so it ‘bulges’ outwards posteriorly.
The thoracic and sacral curvatures are kyphotic.
Explain what lordotic means. Which parts of the spine are lordotic?
Lordotic means it is posteriorly concave so it curves inwards.
The lumbar and cervical curvatures are lordotic.
When do the kyphotic curvatures develop?
During the fetal period. During the foetal period the entire spine is kyphotic!
When does the first lordotic curvature form? Which one is the first?
The first one is the cervical. It forms as the baby starts to be able to held its head up by itself.
When does the second lordotic curvature form? Which one is the second?
The second one is the lumbar. It forms as the baby starts to stand up and walk.
What happens during crawling?
The spine loses its primary kyphosis.
What are the 4 main roles of the vertebral column?
1 - Supports weight of the skull, pelvis, upper limbs and thoracic cage.
2 - Protects the spinal cord and the cauda equina.
3 - Provides an important role in posture and locomotion.
4 - Haematopoeisis.
What does the vertebral foramen contain?
The conus medullaris, cauda equina, the meninges and the spinal cord.
How much of the vertebral body consist of cancellous bone? How much consist of cortical?
90% cancellous
10% cortical
What are the pros of the high cancellous proportion of the vertebral body?
It permits haematopoeisis to take place in a great amount and also makes the spine lighter.
What are vertebral end plates? What are they covered in?
The superior and inferior articular surfaces of the vertebral body. Hyaline cartilage.
Does the size of the vertebrae increase, decrease or stay the same as you descend the spine? Why?
It increases as you get farther down. This is because the lower ones needs to carry the weight of the upper ones, as well as the head, torso etc…
This is in order to resist the increasing compressive load from the structures above.
What is the purpose of the transverse and spinous processes?
To provide attachment points for muscles and ligaments to control the position of the vertebral bodies.
What is the vertebral notch?
Since the articular processes (inferior and superior) are concave their concavity is refereed to as the vertebral notch. Each vertebra has two superior and two inferior vertebral notches.
What is the intervertebral foramen?
The space that is created when two adjacent vertebrae are in their normal anatomical alignment.
Allows passage of the spinal nerves from the spinal canal to the periphery.
What is the facet joint? Also called zygapophyseal.
It is formed between the adjacent superior and inferior articular processes where they meet.
What kind of joint is the facet joint?
A synovial joint that is lined with hyaline cartilage.
What is the amount of flexion and rotation of a facet joint determined by?
The inclination of the articulating surfaces.
What is the inclination of the cervical vertebra?
45 degrees in the axial plane.
What is the inclination of the thoracic vertebra?
60 degrees in the axial plane.
20 degrees in the coronal plane.
What is the inclination of the lumbar vertebra?
90 degrees in the axial plane.
45 degrees in the coronal plane.
What movements does the inclination of the cervical vertebra permit?
Flexion (nodding)
Extension
Lateral flexion (ear to shoulder)
Rotation
What movements does the inclination of the thoracic vertebra permit?
Lateral flexion
Rotation
What movements does the inclination of the lumbar vertebra permit?
Flexion Extension And to some extent: Lateral flexion Rotation
What do the intervertebral discs consist of?
70% water
20% collagen
10% proteoglycans
The intervertebral discs have two regions. Which? Where can they be found?
Nucleus pulposus which is central
Annulus fibrosus which is peripheral
Outline the role and structure of the annulus fibrosus.
It is the major shock absorber of the spine.
Comprises of lamellae.
One lamella has collagen going parallel. But between lamellae the collagen goes in different directions.
The outer lamellae is type 1 collagen and the inner lamellae are fibrocartilaginous.
The annulus fibrosus is avascular and aneural.
It is highly resilient under axial compression.
What is axial compression?
Top to bottom pressure.
The intervertebral discs are stronger than the vertebral bodies under strong axial compression forces. Why is this important clinically?
It means that the vertebral body tends to fracture under axial compression.
What is the origin of the nucleus pulposus?
It is the remnant of the embryonic notochord.
Outline the structure of the nucleus pulposus.
It is gelatinous and consists of type 2 collagen. It has a high oncotic pressure.
It is surrounded by the annulus fibrosus.
What happens to the nucleus pulposus as they day goes on?
It gradually decreases in height as water is squeezed out due to mechanical pressure.
What is the purpose of the ligaments of the vertebral column?
To provide stability by prevent excessive movement of the vertebral column.
In which direction are the ligaments most effective in supporting loads?
In the direction of which their fibres run.
What are the major ligaments? What are the minor ligaments?
Major: Anterior longitudinal ligament Posterior longitudinal ligament Minor: Ligamentum flavum Interspinous ligament Supraspinous ligament
Where can the ALL be found?
Anterior to the vertebral bodies.
Outline the features of the ALLs.
Stronger than the PLL. It runs continuously from the anterior tubercle of the atlas and down to the sacrum where it is united with the periosteum of the vertebral bodies.
What is the function of the ALLs?
To prevent hyperextension of the vertebral column.
Where can the PLL be found?
Posterior to the vertebral body from the boxy of the axis (C2) to the sacral canal.
What are the functions of the PLLs?
Prevent hyperflexion of the vertebral column.
It also reinforces the annulus fibrosus centrally so in case of a intervertebral disc prolapse it tends to occur lateral to the PLL. This is called a paracentral disc prolapse.
Outline the features of the ligamentum flavum.
It has a high elastin content and appears yellow to the naked eye.
Where can the ligamentum flavum be found? What is its function?
Between the laminae of adjacent vertebrae.
It becomes stretched during flexion of the spine.
Outline the features of the interspinous ligaments.
Relatively weak sheets of fibrous tissue that unite the spinous processes along their adjacent borders.
The interspinous ligaments are most prominent in a specific region. Which?
In the lumbar region.
What are the functions of the interspinous ligaments?
To provide stability to the vertebral column by resisting excessive flexion.
Outline the features of the supraspinous ligaments.
A strong band of fibrous tissue.
Where can the supraspinous ligaments be found?
Runs along the tips of the spinous processes.
What is the function of the supraspinous ligament?
Increasing stability of the vertebral column.
How does the distribution of body weight carried differ as we age? Why?
When we are young 80% of body weight is transmitted through the vertebral bodies and 20% through the facet joints.
As we age the nucleus pulposus will start to dry out more and more and this means it will decrease in size. This causes the body weight transmission to shift from the vertebral bodies to the facet joint so 65% might be transmitted via the vertebral bodies and 35% through the facet joints.
What is the consequence in the shift of body weight transmission from the vertebral bodies to the facet joints.
It causes narrowing of the synovial facet joint. This means that it is an osteoarthritic change that is similar to those in the knees and hips. This can result in back pain.
Outline the structure of the sacrum.
Consists of five FUSED vertebrae. Situated inferior to the L5 and superior the coccyx. The ilium of the pelvis can be found laterally to the sacral region.
Outline the structure of the coccyx.
Consists of four FUSED vertebrae. Situated inferior the sacrum.
Explain where you can find the central canal of the vertebral column in the sacral region.
It continues along the core of the sacrum and ends at the fourth sacral vertebra as the sacral hiatus.
Where is the cauda equina?
It can be found inside the central canal. It is a bundle of spinal nerve rootlets fibres that is found from L2 to L5 in the lumbar region. S1 to S5 in the sacral region and also the coccygeal nerve.
What do the nerves the compose the cauda equina innervate?
The pelvic organs like the bladder for instance as well as the lower limbs.
How do the sacral nerve fibres enter and leave the central canal?
By the way of the four pairs of posterior sacral foramina. The transverse processes of the five sacral vertebrae are not completely fused which means that the sacral nerve fibres can enter and exit there.
What is the filum terminale?
A continuation of the Pia mater from the conus medullaris of the spinal cord to the first segment of the coccyx.
What does the vertebral column look like as a foetus?
It is C-shaped, concave anteriorly.
What is the primary curvature? Can it be found in adults?
The anteriorly concave region found in foetuses. It is retained throughout life in the thoracic, sacral and coccygeal regions.
What is an anteriorly concave or anterior flexion curvature known as?
Kyphosis.
What is a posterior flexion or posteriorly concave curvature known as?
Lordosis.
What are the secondary curvatures?
The lordoses of the cervical and lumbar regions.
How is the cervical lordosis formed?
It is formed when a baby starts to be able to hold its head up by itself.
How is the lumbar lordosis formed?
As a child begins to stand up and walk it is formed.
When do we lose our primary curvature?
As we begin to crawl.
How many kyphoses are there? Which?
Two:
Thoracic
Sacrococcygeal
How many lordoses are there? Which?
Two:
Cervical
Lumbar
What is senile kyphosis?
The re-establishment of a continuous primary curvature. This is due to wear and tear of the annulus fibrosus and dehydration and degeneration of the nucleus pulposus. In short: disc atrophy.
The centre of gravity passes through the vertebral column at four sites. Which?
C1/C2
C7/T1
T12/L1
L5/S1
Why are these four sites important?
Because they are weak points of the vertebral column at which pathology tends to develop.
