The Back Flashcards
What are the landmarks of the back?
The back has several key landmarks that are bony in nature. It runs from the first thoracic vertebrae (T1) to the coccyx, and from the medial border of the scapula along the posterior surface of the ribs down to the iliac crest.
How much of the body surface does the back make up?
It makes up around 18% of the body surface.
What are the compartments of the back?
The back is arranged into the vertebral column and 2 muscular compartments (superficial/extrinsic & deep/intrinsic)
Explain the development of the vertebral column.
During development, the foetal spine is C-shaped in curvature (kyphotic) and secondary curves (lordotic) develop in the cervical region (when the baby begins to lift its head) and the lumbar region (when walking begins).
What are the kyphotic and lordotic curves of the spine?
KYPHOITIC CURVES: Thoracic & sacro-coccygeal
LORDOTIC CURVES: Cervical & Lumbar
What are some abnormalities of the spine?
Abnormalities can occur in the curvatures of the vertebral column such as Lordosis (over curvature of the lumbar region such as during pregnancy), Kyphosis (over curvature of the thoracic region - hunching) or Scoliosis (spine curves laterally)
Give the general features of a typical lumbar vertebrae.
Body: size increases from L1 - L5; they are weight bearing
Epiphyseal ring: situated internally in the vertebral body
Vertebral foramen: posterior to vertebral body, creates the vertebral canal
Processes: extensions for ligament attachments
Vertebral arch: encloses space for the vertebral canal. (has lamina (dorsal) & pedicles)
Articular Processes: in lumbar vertebrae, the articular processes are joined in facet joints/zygapophysial joints, therefore they are lines with hyaline cartilage. These facet joints limit movement and protect the segment from excessive rotation and flexion. There is a facet capsule around the joint for protection.
What are some key features of the thoracic vertebrae?
Demifacets: for articulation of the head of two ribs (above and below)
Intervertebral foramen: between two adjacent vertebrae
Foraminae: openings for basivertebral veins. These veins have no valves; allow for flow in both directions (easy communication). This can make it easy for cancerous cells to spread into the vertebral column due to no valves.
What are some key features of the sacrum and coccyx?
Sacrum: five fused vertebrae, the S1 facet surfaces are in the coronal plane; has anterior and posterior sacral(IV) foraminae - for nerve roots and vessels (including sacral veins)
Coccyx: There an be a variable number of coccygeal vertebrae.
What are the centres of ossification?
There are three primary centres in the body and each natural arch of the vertebrae. At puberty there are 5 secondary centres at the tips of spinous & transverse processes and upper/lower margins of the body (annular epiphysis)
The secondary centres normally close during late adolescence when the vertebral growth is complete.
What are some key joints of the back?
IV discs
Lumbosacral
Facet joints
Explain the two elements of an intervertebral disc
Nucleus Pulposis: acts as a shock absorber and keeps the vertebrae separated. Weight bearing forces cause the nucleus to bulge.
Annulus Fibrosis: distributes the pressure evenly across the discs and keeps the vertebrae together.
As an individual ages, the water content of the nucleus diminishes. The annulus is in layers of fibrocartilage which are perpendicular to each other meaning that the leads are easier to take at various angles (twisting whilst lifting is dangerous as only 50% of fibres are positions to resist the load)
The recurrent meningeal nerve (sensory & sympathetic fibres) innervates the disc, but only the outer third receives vessels and nerves.
What are some features of Facet Joints/ Zygapophysial Joints?
In lumbar vertebrae, articular facets are joined for stability and limiting movement.
The synovial joint is surrounded by a fibrous capsule and is innervated by branches of the posterior ramus of two successive nerve roots (which also supply intrinsic muscles and skin of the posterior trunk)
The orientation of the facet surfaces dictate the direction of movements.
What is significant about a fracture of the lumbosacral joint?
A fracture to the pars interarticularis can cause spondylolisis and listhesis of L4 on L5 and L5 on S1 which can be a source of lower back pain and may result in one vertebrae slipping forward in relation to an adjacent vertebrae.
What are the contents of the vertebral canal?
Contains the spinal chord, which extends from the brain stem and terminates at L1/L2. There are also 33 vertebrae but only 31 spinal nerves (8C, 12T, 5L, 5S, 1Cox)
Spinal nerve roots leave the spinal chord (ant-motor; post-sensory) and combine to create a spinal nerve which leaves the vertebrae through the intervertebral foramen. The dorsal root ganglion is usually seen at the intervertebral foramen.
The spinal chord is surrounded by meninges (dura, arachnoid, pia mater). The dura and the arachnoid terminate at S1 but the pia extends to the coccyx forming the filum terminale. Since the spinal nerves extend beyond the termination of the spinal chord, these nerves for a structure called the cauda equina that is a bundle of nerves all originating from conus medullaris.
What are the ligaments of the vertebral column?
Longitudinal: lie along the ANT and POST sides of the vertebral body (expanding over the IV discs.
Ligamentum Flavum: lines the POST wall of vertebral canal between the vertebrae, connecting the lamina of adjacent vertebrae. This consists of yellow elastic tissue which are almost perpendicular in direction. This elasticity serves to preserve the upright posture and assist the vertebral column in resuming it after flexion. It prevents buckling of the ligament into the spinal canal during extension.
Supraspinous: across the POST surface of spinous processes
Interspinous: between spinous processes of adjacent vertebrae
Intertransverse: Between transverse processes
Give an explanation of blood supply and drainage of the back.
Blood supply comes from the posterior intercostals, lumbar arteries and lateral sacral arteries. Blood then drains to the external vertebral venous plexus.
What is a lumbar puncture used for?
Epidural Anaesthesia is used to block spinal nerves for abdominal, pelvic and LL surgery. Especially common for pain relief during childbirth.
What is Spina Bifida?
Occurs when the sacral region of vertebrae do not fuse appropriately and can lead to LL sensory & motor loss, incontinence and even a herniated spinal chord/nerves.
Where in the back does the movement flexion occur?
mainly occurs in the lumbar spine and is enhanced by lumbar lordosis. Flexion causes the nucleus to project posteriorly. Hyperflexion stretches the sciatic nerve and may cause nerve root pain.
Where in the back does the movement extension occur?
In extension, the thoracic spine has minimal movement (retains kyphosis) but the lumbar spine increases lordosis. Hyperextension increases stress on facet joints.
Where in the back does the movement lateral flexion occur?
There is a small degree of lateral flexion in the thoracic spine but its limited by the ribs. Mostly occurs in the lumbar spine. A similar pattern is seen in Rotation.
What influences movements in the back>
Movements of the back are influenced by:
- Thickness of IV discs - enhance movement (may be wedge shaped) - Orientation of the articular facets - designed to limit movement to certain directions (thoracic allow coronal rotation; lumbar allow flexion/extension in sagittal plane; Lumbosacral limit movement in sagittal plane.)
What are the superficial muscles of the back?
How are they innervated?
All attach and act on the upper limb. They include trapezius, latissimus dorsi, rhomboids & levator scapulae. The superficial muscles of the back all originate from cervical myotomes and are all innervated by the anterior rami, except for trapezius which is innervated by a cranial nerve.
The posterior rami penetrates but does not supply the superficial muscles, instead passing through to the skin.
