The lumbar spine Flashcards
Describe the vertebral column?
Seven cervical vertebrae
Twelve thoracic vertebrae
Five lumbar vertebrae
Five sacral vertebrae
Four coccygeal vertebrae.
How does the vertebrae in the sacrum and coccyx differ?
Sacrum comprises five fused vertebrae and the coccyx comprises four fused vertebrae.
What are the 4 function of the vertebral column?
Support – of the the skull, pelvis, upper limbs and the thoracic cage.
Protection - of the spinal cord and the cauda equina
Movement - Highly flexible structure of bones, intervertebral discs and ligaments
Haemopoiesis – Within red marrow
Label
What does the vertebral foramen contain?
The conus medullaris, cauda equina and meninges)
What is the vertebral arch?
What does it give rise to?
Vertebral arch = 2 laminae + 2 pedicles
Gives rise to 7 processes
1 Spinous process
2 Transverse processes
2 Superior articular processes
2 Inferior articular processes
What are posterior elements?
collective name for all structures posterior to vertebral body
Describe the vertebral body and its compisition?
10% cortical bone , 90% cancellous bone
Cancellous bone reduced the weight and permits haemopoesis to take plac
What is the function of the transverse and spinous processes?
Provide attachment points for muscles and ligaments to control the position of the vertebral bodies.
Their shape provides a leverarm to provide the system with mechanical advantage
How does the inferior articular process project?
Caudally (towards tail)
How does the superior articular process project?
In a cephallic direction
(towards head)`
Describe the zygapophyseal (facet) joint?
Formed between adjacent superior and inferior articular processes is a synovial joint, lined with hyaline cartilage.
The interlocking design of the facet joints prevents antero-posterior (forward-backward) displacement of the vertebrae
Describe the articulating facets in the cervical vertebrae?
Aligned at 45° to the axial (transverse) plane and are in the coronal plane with the superior articulating process facing posterior and up, and the inferior articulating processes facing anterior and down.
These permit flexion (nodding), extension, lateral flexion (ear towards shoulder tip) and rotation
Describe the articulating facets in the thoracic vertebrae?
The facet joints are angled at 60° to the axial plane and 20° to the coronal plane, with the superior articulating process facing posterolaterally (specifically, posteriorly and laterally by 20° from the coronal plane) and the inferior articular process facing anteromedially (anteriorly and 20° medially).
These permit lateral flexion and rotation but no flexion or extension
Describe the articulating facets in the lumbar vertebrae?
Facet joints lie perpendicular to the transverse plane and at 45° to the coronal plane.
The superior facets face posteromedially (specifically, posteriorly and 45° medially) and the inferior facets face anterolaterally (anteriorly and 45° laterally).
The major movements permitted in the lumbar spine are flexion and extension.
This changes at the lumbosacral junction where the inferior facet on L5 faces anteriorly.
This change in orientation prevents the vertebral column from sliding anteriorly on the sacrum
Describe the two regions of intervertebral disks?
Nucleus pulposus which is central. Remains of embryonic notochord - gelationous and consists of T2 collagen. High oncotic pressure - decreases in height during day
Annulus fibrosus which is peripheral. Consists of lamella in varying oreintations, outer = T1 collagen, inner fibrocartilaginous, avascular and aneural highly resistant under axial copression
Describe the anterior longitudinal ligament?
It runs continuously from the anterior tubercle of the atlas (C1 vertebra) to the sacrum
United with the periosteum of the vertebral bodies. Over the intervertebral discs, it is loosely attached and mobile. Its function is to prevent hyperextension of the vertebral column.
Describe the posterior longitudinal ligament ?
Runs posterior to the vertebral bodies, from the body of the axis (C2 vertebra) to the sacral canal.
Superior to the axis, it continues as the tectorial membrane of the atlanto-axial joint (a strong band which covers the dens of the axis).
It prevents hyperflexion of the vertebral column.
Its main relevance clinically is that it reinforces the annulus fibrosus centrally so that intervertebral disc prolapse tends to occur lateral to the posterior longitudinal ligament. This type of prolapse is called a paracentral disc prolapse.
Describe the Ligamentum flavum?
High elastin content and appears yellow to the naked eye (Flava = yellow in Latin).
It is situated between the laminae of adjacent vertebrae and becomes stretched during flexion of the spine.
Describe the interspinous ligaments?
Relatively weak sheets of fibrous tissue that unite the spinous processes along their adjacent borders.
They are most highly developed in the lumbar region, where they increase the stability of the vertebral column by resisting excessive flexion.
Describe the supraspinous ligament?
Runs along the tips of the adjacent spinous processes.
Strong band of fibrous tissue.
It is lax in extension and taught in flexion, further increasing the stability of the vertebral column.
Describe the sacrum?
- Sacrum consists of 5 fused vertebrae
- Articulates with L5 superiorly, ilium laterally, and coccyx inferiorly
- Contains cauda equina
- Spinal nerves exit spinal canal via the sacral foramina and sacral hiatus
Describe the coccyx
Coccyx consists of 4 fused vertebrae
Easily fractured during falls
Remnant of ‘tail
What is a kyphosis?
. An anterior flexion (or anteriorly concave) curvature
What is a lordosis?
A posterior flexion (or posteriorly concave) curvature
Describe the patterns of spinal curvature throught life?
Primary curvature fetus - c shaped
As child lifts its head - cervical develops a posterior concavity
Crawling - lumbar spine loses its primary kyphosis and straightens out.
Standing up and walking - lumbar lordosis develop
Increasing age - the annulus fibrosis of the intervertebral discs begins to undergo degeneration (because of wear and tear). The nucleus pulposus loses its turgor and becomes thinner because of dehydration and degeneration.
Primary curvature - senile kyphosis
What happens to the curvature of the spine during pregnancy
Exaggeration of lumbar lordosis during pregnancy
Restores centre of gravity
Describe the centre of gravity?
The centre of gravity of the body is projected into the lower limbs through a line that passes centrally through the natural curvatures of the vertebral column
In an adult standing erect, the centre of gravity of the body passes through the vertebral column at four sites C1/2, C7/T1, T12/L1 and L5/S1
These are the ‘weak points’ of the vertebral column at which pathology tends to develop.
