Anatomy - Intro to the Spine Flashcards
Vertebral column
Central foundation of the skeleton
Provides support for head and trunk and attachments for muscles and protects spinal cord
What is the vertebral column composed of
33 separate vertebrae, stacked and grouped into 5 regions - neck, chest, lower back, sacrum, coccygeal
Vertebrae in neck
5 cervical vertebrae
Vertebrae in chest
12 thoracic vertebrae
Vertebrae in lower back
5 lumbar vertebrae
Sacral vertebrae
5 vertebrae fused with sacrum
Coccygeal vertebrae
4 coccygeal vertebrae are vestigial remand of tail
Provides attachment for ligament
Why does a healthy vertebral column have a series of gentle curves
Important for maintaining upright posture and help dissipate forces travelling through the spine
Kyphosis
Vertebrae in chest and sacrum curve forwards
Lordoses
Vertebrae in neck and lower back curve backwards
When does cervical lordosis form
Whole spine is kyphotic at birth, cervical lordosis forms after few months to allow baby to hold head up independently
When does lumbar lordosis form
Within year allows baby to support body weight over hips and walk
What does the vertebral body provide attachment for
The disc that sits between the vertebrae
Vertebral canal
Where spinal cord is found, safely protected by thbone around it
Bony projections of vertebra
2 lateral transverse processes and posterior spinous process provide attachments for muscles of the back
Usually, can be palpated, can feel spinous process of 7th cervical vertebrae
Superior and inferior articular facet
Form joints with articular facets of the vertebrae above and below and these joints guide movements of the spine
Intervertebrate foramen
Created by articular facets joining togethe
Creates path for spinal nerves to leave the vertebral canal and enter the body
Features of vertebrae
Spinous process Lamina Articular facet Pedicles Vertebral body Vertebral canal Transverse process Spinous process
What are cervical vertebrae characterised by
Foramen transversarium
Bifid spinous process
Foramen transversarium
2 small holes in their transverse processes
Provides a safe route for vertebral artery to travel along the neck
What are thoracic vertebrae characterised by
Coastal facets
Coastal facets
Form joints with heads of ribs - superior coastal facet and transversp-coastal facets
Transverso-coastal facets articulate with the tubercles of the ribs
Features of lumbar vertebrae
Most robust, with large, wide bodies and transverse/ spinous processes
Processes are particularly prominent (need powerful muscles to move them)
Atypical vertebrae
C7 has both cervical and thoracic features and T12 has mix of thoracic and lumbar
Atlas
Axis
Atlas
1st cervical vertebrae
Axis
2nd cervical vertebrae
Atlas and axis comparison
Both have transverse processes but reduced in size
Atlas doesn’t have spinous process or vertabral body
Axis has dense/ odontoid peg
Dense/ odontoid peg
Upward-pointing projection of bone
Movements of spine
Flexion
Extension
Lateral flexion (to either side)
Rotation
What determines types of movement available at each section of spine
Joints
Movement at thoracic spine
Mainly lateral flexion
Movement of lumbar spine
Mainly flexion/ extension
Intervertebral disc
Cartilaginous joints connecting vertebral bodies together
Components of IVDs
Nucleus pulposus
Annulus fibrosis
Vertebral endplate
Nucleus pulposus
Central gelatinous mass formed of mainly type II collagen
Equal distribution of the force so it can be resisted
Function of IVD
Allow movement between adjacent vertebral bodies
Absorb shock
Transmit loads through the vertebral column
Number of IVDs in spine
23
IVDs in cervical region
6
IVDs in thoracic region
12
IVDs in lumbar region
5
Key note about IVDs
There is no intervertebral disc between C1 (atlas) and C2 (axis)
Absent in sacral and coccygeal region
Annulus fibrosis
Fibrous outer ring formed of mainly type I collagen arranged in lamellae.
The annulus fibrosus is the primary load-bearing component of the intervertebral disc
Innervation of IVDs
Receives innervation from the outer third portion of the annulus fibrosus
Vertebral end plate
Cartilaginous layer covering the inferior and superior surfaces of the intervertebral disc
How do IVDs receive nutrients
Avascular structure so endplate permits diffusion and provides the main source of nutrition for the disc
Atlanto-occipital joint
Joint between C1 and occipital bone
Holds weight of head, allows head to rock backward and forward
Atlanto-axial joint
Joint found between atlas and axis
How does atlas and axis fit together
Odontoid peg fits into where vertebral body should be, traverse ligament passes through here and allows axis to rotate
Actions of erector spinae
Extension
Lateral flexion
Anterior nerve root
Ventral
Posterior nerve root
Dorsal
Function of dorsal ramus
Small posterior branch of spinal nerve supplies skin and muscles of back
Function of ventral ramus
Larger anterior branch supplies everything else in body
Anything distal to spinal nerve leaves …
Protection of bony canal
Somatic nervous system
Voluntary nervous system
Effernet nerves
Exit spinal cord
Motor supply
Afferent nerves
Arrive at spinal cord
Sensory supply
Dorsal root ganglion
Cluster of afferent cell bodies
What do rami and spinal nerves contain
Mix of efferent and afferent fibres
What do nerve roots contain
Eferent or afferent nerves
Where are afferent nerves found
Ventral root
Where are efferent nerves found
Dorsal root
Where are symptoms of nerve damage experienced
Distal to injury
What happens if spinal nerve is damaged
Efferent impulses can’t get out and afferent cant get in so we lose all innervation in both rami
What happens if rami is damaged
Lose motor and sensory supply of that rami
What happens if ventral root is damaged
Lose efferent innervation beyond that point in both rami so no motor supply but sensory supply is fine
What happens if dorsal root is damaged
No sensory supply but motor is fine
Commonest cause of back injury
Lifting heavy object - advised to keep back straight and let legs do the work
How can IVDs be damaged
When lifting with bent spine as work best when spine is straight and forces spread out evenly. When flexed, forces are disproportionately channeled though anterior portion of the disc —> nucleus pulposus being pushed out and prolapsing though annulus fibrosis
When do the erector spinae muscles have to work harder
Have to work harder to extend and support spine when not lifting with straight back
What can cause tear of erector spinae muscles
Extensive strain due to smaller and more medial muscles supporting the spine as in flexion, lateral erector spinae muscles pass anteriorly and become flexors
Cross section of lumbar IVDs
More elliptical shaped to help resist bending movements
Cross section of thoracic IVDs
More circular, making them better suited to distributing the force of tension more equally, so stronger forces can be withstood
Disc pathology
Disc bulge
Disc herniation
Desiccation
Prolapse
Disc bulge
The circumference of disc extending beyond the vertebral bodies
Disc desssication
Common in aging
NP shrinks as gelatinous material is replaced by fibrotic tissue and AF increases in size as a result of the additional pressure
Disc prolapse
Rupture of nuclear material into the vertebral canal
Disc sequestration
Herniated material break off from the body of the nucleus pulposus
How does the spine cord arise cranially
As a continuation of the medulla oblongata
Cervical enlargement
1st point of enlargement on spine Cervical enlargement (C4-T1) Origin of the brachial plexus
Lumbar enlargement
2nd point of enlargement Lumbar enlargement (T11-L1) Origin of the lumbar and sacral plexi
What does film terminate attach to
Vertebral bodies of the coccyx, acting as an anchor for the spinal cord and meninges
