MSK session 8 - Vertebral Column and Lumbar Spine Flashcards
(39 cards)
What is the vertebral column?
The vertebral column is a vertical series of approximately 33 small bones (known as vertebrae), which are separated by intervertebral discs. It can be separated into five different regions, with each region characterised by a different vertebral structure.
What are the five main functions of the vertebral column?
- Protection – encloses and protects the spinal cord and the cauda equina within the spinal canal.
- Support – carries the weight of the body above the pelvis.
- Axis – forms the central axis of the body.
- Movement – highly flexible structure of bones, intervertebral discs and ligaments, has roles in both posture and movement.
- Haemopoiesis – red bone marrow
Identify the sections of the vertebral column.
- Cervical (7)
- Thoracic (12)
- Lumbar (5)
- Sacrum (5, fused)
- Coccyx (4, fused)
Outline the vertebral structure.
All vertebrae share a basic common structure. They each consist of a vertebral body, situated anteriorly, and a posterior vertebral arch.
Outline the structure, function and components of the vertebral body.
- The vertebral body is the anterior part of the vertebrae. It is the weight-bearing component, and its size increases as the vertebral column descends (having to support increasing amounts of weight).
- The superior and inferior aspects of the vertebral body are lined with hyaline cartilage. Adjacent vertebral bodies are separated by a fibrocartilaginous intervertebral disc.
Outline the structure of the vertebral arch.
- The vertebral arch refers to the lateral and posterior parts of the vertebrae.
- With the vertebral body, the vertebral arch forms an enclosed hole, called a vertebral foramen.
- The foramina of the all vertebrae line up to form the vertebra canal, which encloses the spinal cord.
The vertebral arches have a number of bony prominences, which act as attachment sites for muscles and ligaments. Identify them.
- Pedicles: There are two of these, one left and one right. They point posteriorly, meeting the flatter laminae.
- Lamina: The bone between the transverse and spinal processes.
- Transverse processes: These extend laterally and posteriorly away from the pedicles. In the thoracic vertebrae, the transverse processes articulate with the ribs.
- Articular processes: At the junction of the lamina and the pedicles, superior and inferior processes arise. These articulate with the articular processes of the vertebrae above and below.
- Spinous processes: Posterior and inferior projection of bone, a site of attachment for muscles and ligaments.
Outline the structure, function and role of cervical vertebrae.
- There are seven cervical vertebrae in the human body. They have three main distinguishing features:
I. The spinous process bifurcates into two parts, and so is known as a bifid spinous process.
II. There are two transverse foramina, one in each transverse process. These conduct the vertebral arteries.
III. The vertebral foramen is triangular in shape
There are some cervical vertebrae that are unique. C1 and C2 (called the atlas and axis respectively), are specialised to allow for the movement of the head. The C7 vertebrae has a much longer spinous process, which does not bifurcate.
Outline the structure, function and role of thoracic vertebrae.
- The twelve thoracic vertebrae are medium-sized, and increase in size as they move down the back. Their main function is to articulate with ribs, producing the bony thorax.
- Each thoracic vertebrae has two ‘demi facets‘ on each side of its vertebral body. These articulate with the head of the respective rib, and the rib inferior to it. On the transverse processes of the thoracic vertebrae there is a costal facet for articulation with its respective rib.
- The spinous processes are slanted inferiorly and anteriorly. This offers increased protection to the spinal cord, preventing an object like a knife entering the spinal canal through the intevertebbral disc.
- In contrast to the cervical vertebrae, the vertebral foramen is circular.
Describe the characteristic features of the lumbar vertebrae.
- These are the largest of the vertebrae, of which there are five. They act to support the weight of the upper body, and have various specialisations to enable them do this.
- Lumbar vertebrae have very large vertebral bodies, which are kidney-shaped. They lack the characteristic features of other vertebrae, with no transverse foramina, costal facets, or bifid spinous processes.
- However, like the cervical vertebral, they have a triangular shaped vertebral foramen
Describe the characteristic features of the sacrum and coccyx vertebrae.
- Sacrum is a collection of five fused vertebrae. It is described as an upside-down triangle, with the apex pointing inferiorly. On the lateral walls of the sacrum are facets, for articulation with the pelvis at the sacro-iliac joints.
- Coccyx is a small bone, which articulates with the apex of the sacrum. It is recognised by its lack of vertebral arches. Due to the lack of vertebral arches, there is no vertebral canal, and so the coccyx does not transmit the spinal cord.
Describe the structure of the major joints of the vertebral column.
- For every vertebrae, there are five articulations. The vertebral bodies indirectly articulate with each other, and the articular processes also form joints.
- The vertebral body joints are cartilaginous joints, designed for weight-bearing.
- There are two ligaments that strengthen these joints; the anterior and posterior longitudinal ligaments.
- The anterior longitudinal ligament is thick and prevents hyperextension of the vertebral column.
- The posterior longitudinal ligament is weaker and prevents hyperflexion.
- The joints between the articular facets are called facet joints. These allow for some gliding motions between the vertebrae. They are strengthened by various ligaments:
I. Ligamentum Flavum
II. Interspinous ligaments
III. Supraspinous ligaments
IV. Inter transverse ligaments
Outline the structure and function of the ligamentum flavum.
Ligamentum Flavum:
- Extends from lamina to lamina.
- Yellow in colour, composed of elastic fibres.
- Between laminae of adjacent vertebrae.
- Stretched during flexion of the spine.
Outline the structure and function of the interspinous ligaments.
Interspinous ligaments:
- Relatively weak sheets of fibrous tissue
- Unite spinous processes along adjacent borders
- Well-developed only in the lumbar region (stability in flexion)
- Fuse with supraspinous ligaments
Outline the structure and function of the supraspinous ligaments.
Supraspinous ligaments:
- Tipis of adjacent spinous processes
- Strong bands of white fibrous tissue
- Lax in extension
- Tight in flexion (mechanical support for vertebral column)
Outline the structure and function of the inter transverse ligaments.
Inter transverse ligaments: extends between transverse processes.
Outline the structure, function and role of intervertebral discs.
- Account for 25% of the length of the vertebral column
- Fibrocartilaginous discs: 70% Water, 20% Collagen, 10% Proteglycans
- Lose height with age
- Consist of two regions:
I. Nucleus pulposus (central)
II. Annulus fibrosus (peripheral)
What is the annulus fibrosis?
- Highly complex design
- Made from lamellae of annular bands in varying orientations
- Outer lamellae Type 1 collagen
- Inner lamellae are fibrocartilaginous
- Avascular and aneural
- Surrounds nucleus pulposus
- Is the major ‘shock absorber’
- Highly resilient under compression - stronger than the vertebral body
What is the nucleus pulposus?
- Remnant of notochord
- Gelatinous, Type 2 Collgen
- High osmotic pressure
- Changes in size throughout day
- Changes in size with age
- Surrounded entirely by annulus fibrosus
- Centrally located in the infant
- Located more posteriorly in the adult
What is the anterior longitudinal ligament?
- Anterior tubercle of atlas to sacrum
- United with periosteum of vertebral bodies
- Mobile over intervertebral discs
- Prevents hyperextension
What is the posterior longitudinal ligament?
- Body of axis to sacral canal
- Continues superior to axis as ‘tectorial membrane’
- Relatively weak
- Prevents hyperflexion
- Position dictates where disc prolapse
Describe the pathophysiology of mechanical back pain.
- Pain when the spine is loaded
- Worse with exercise relieved by rest
- Natural History:
I. Intermittent
II. Often triggered by innocuous activity
III. Predisposition overweight, unhealthy lifestyle, deconditioned core muscles
- Behavioural modifiers (mental health)
I. Benefits
II. Accident
III. Fear/Beliefs
IV. Job
V. Relationship
Describe the pathophysiology of ‘slipped disc’
- Disc Degeneration: chemical changes associated with aging cause discs to dehydrate and BULGE
- Prolapse: protrusion of the nucleus pulposus with slight impingement into the spinal canal (contained)
- Extrusion: nucleus pulposus breaks through annulus fibrosus, but remains within the disc space.
- Sequestration: nucleus pulposus breaks through annulus fibrosus and separates from the mai n body of the disc in the spinal canal.
- Most commonly occurs at L4/5 or L5/S1
- Usually herniates posterolaterally, causing compression of spinal nerve roots
What are the types of disc prolapse?
- Lateral disc protrusion usually compresses the nerve root above
- Paracentral disc protrusion usually compresses the nerve root below (most common)
