Vertebral Column 3 Flashcards
how many articular facets are there per vertebra
4 –> 2 cranial and 2 caudal
what is the orientation of the articular facets
cranial facets lateral/ventral to caudal facets
what are the exceptions to the synovial joint features (3)
- atlanto-occipital joint where the atlas or C1 articulates with the occipital condyles of the skull rather than adjacent vertebra
- sacrum –> bones are fused into single bone unit –> articular facets and associated joints are absent
- caudal/coccygeal region –> vertebra have reverted to more basic form and have lost many of features associated with typical vertebra including articular facets
what are the features of synovial joints
synovial fluid is present between articular surfaces
produced by synovial membrane and contained within the joint capsule
stabilized by ligaments and movement across joints produced by action of muscle
what is the intervertebral disc made up of
- annulus fibrosus
- nucleus pulposus
what is the annulus fibrosus
series of concentric rings of fibrous tissue arranged in rigns (like onion)
fibres run between endplates of adjacent vert bodies –> holding them together + providing stability by restricting stretching of intervertebral disc space
what is the nucleus pulposus
notochord remnant –> involved with embryological development of vert column
jelly filled cushion embedded within annulus fibrosis and surrounded by it –> shock absorption and resists compression of disc space
where is the intervertebral disc space weakest
annulus thinnest dorsally
what structures shown
- annulus fibrosus
- nucleus pulposus
what are the intervertebral ligaments
- dorsal longitudinal ligament
- ventral longitudinal ligament
- interspinous ligaments
- interarcuate/yellow ligament
- supraspinous ligament
- nuchal ligament - dog
where does the dorsal longitudinal ligament run
along the dorsal aspect of the vertebral bodies –> ventral floor of the vertebral canal
along the entire length of the vertebral column from the level of C2
name the ligaments shown
- dorsal longitudinal ligament
- ventral longitudinal ligament
- invertebral disc
- interspinous ligaments
- interarcuate/yellow ligament
where does the ventral longitudinal ligament run
ventral aspect of the vertebral body and is present from the level of C2 to the sacrum
where does the supraspinous ligament run
along dorsal aspect of dorsal spinous processes and is present from level of T1 to CC3
in dog it continues in cranial driection to caudal aspect of axis or C2 as a cord of fibroelastic material called nuchal ligament
what is the function of the nuchal ligament
passive support for the large weight of head
how does the nuchlar ligament differ in horses
heavier head –> 2 parts
- funicular part = cord: fibro-elastic band of tissue (present in dog) is a continuation of supraspinous ligament runs all the way to nuchal crest of skull
- laminar part = fenestrated sheet: run from funicular part of nuchal ligament to dorsal spinous processes of cervical vertebrae
what is present near the nuchal ligament in horses
- fluid filled bursa –> atlantal bursa (located between nuchal ligament and atlas/C1
- supraspinous bursa –> dorsal to the dorsal spinous processes of the first few thoracic vertebrae
what are the ribs held in place by
costal ligaments
where does the intercapital ligament run
between the heads of each pair of corresponding left and right ribs
runs over dorsal surface of intervertebral disc space and merges with fibres of dorsal longitudinal and annulus fibrosis of intervertebral disc
what is the function of the intercapital ligament
stabilizes the ribs and the intervertebral disc
what ribs is the intercapital ligament associated with
1-10
why do ribs 11-13 not have the intercapital ligament
they articulate only with the vertebral body of the corresponding vertebra and don’t span the intervertebral disc space –> ligament is absent
what does the tuberculum of each rib held in place by
articulates with short transverse process of corresponding vertebra and held in place by costo-transverse ligament
what ligament holds the ribs in place ventrally
radiate ligament that supports the joint capsule and merges with fibres of annulus fibrosus of intervertebral disc space
how does the vertebral column move with minimal damage
restricted movement between bones
cummulative effect over length of section
transitional areas most susceptible to damage
what is the atlanto-occipital joint
atlas/C1 and occipital condyles of skull
limited to flexion and extension by wings of C1 (large transverse processes)
‘yes’ joint
what is the atlanto-axial joint
formed between C1 and C2
dens of C2 sits on ventral floor of the vertebral foramen of C1 and held in place by transverse ligament
large dorsal spinous process of C2 limits to lateral rotation
‘no’ joint –> sideways shaking motion
what is the occipito-atlanto-axial complex
combination of atlanto-occipital and atlanto-axial joints –> allows a ful 360 range of movement but spreads it over the length of 2 joint spaces
reduces the chance of spinal cord damage due to excessive movement
how does disc degeneration occur
the intervertebral discs are subjected to compressive and distractive forces as they function like shock absorbers between the adjacent vertebral bodies
can occur either as an age related change or spontaneously in some breeds such as the Dachshund which are predisposed to it
nucleus pulposus becoming dehydrated and this reduction in fluid content means that it is no longer hyperintense or bright white on MR images but appears dark, similar to the annulus fibrosis. This results in the disc loosing some of its compliance which can predispose it to further damage.
what is disc protrusion
disc material bulges dorsally from the disc space pushing the dorsal longitudinal ligament into the vertebral canal
why does disc protrusion always occur in a dorsal direction
annulus fibrosis is thinner dorsally than ventrally
how does disc protrusion occur
due to trauma but dogs with degenerative discs may be predisposed to this as the nucleus pupolsus is more rigid and less flexible than normal
what is disc extrusion occur and why is it a serious condition
disc ruptures through the dorsal longitudinal ligament and disc material becomes located within the vertebral canal itself.
not much space in the vertebral canal and therefore a very real risk that this material will cause compression of the spinal cord itself
where are disc protrusion and extrusion most commonly found
degeneration can affect any disc along the length of the vertebral column but protrusion and extrusion –> most movement possible –> cervical and lumbar regions and thoracolumbar junction (transition area of low motion to high motion)
why is the lumbo-sacral region not affected by disc problems
the spinal cord terminates in the lumbar region of the vertebral column, it would not be affected by disc disease at this level
where are uncommon regions of disc disease
areas of low motion –> thoracic (also because the intercapital ligament from T1-10 that helps stabilise the disc)
sacrum is a single fused unit with no disc spaces and therefore will not be affected
what are the diseases
- disc degeneration
- disc protrusion
- disc extrusion
what is the vertebral formula of the dog
C7 T13 L7 S3 CC variable
name the vertebrae
cervical
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what is the vertebral formula of cat
C7 T13 L7 CC variable
what are the differences in feline vertebrae
more slender bones
vertebral bodies appear longer and finer on radiographs
more flexible column
what is the vertebral formula of the horse
C7 T18 L6 S5 CC variable
what are the species differences in the horse vertebrae (9)
- 18 pairs of ribs –> 18 thoracic vertebrae
- 6 lumbar vertebrae and 5 sacral vertebrae (fused to form sacrum)
- cervical region remains flexible to allow large range of movement of head
- longest dorsal spinous process is T6 (withers)
- anticlincal vertebra is T16 (thoracic vertebra with shortest and most vertically orientated dorsal spinous process)
- transverse processes are very large in the lumbar region –> abdominal muscle attachment
- intertransverse joints + ligaments to support abdominal weight
- sacrum –> dorsal spinous processes separate
- lumbosacral joint –> vulnerable to damage, propulsion from hindlimbs
what is the vertebral formula in the cow
C7 T13 L6 S5 Cc variable
what are the species variation of the cow vertebrae
- fewer ribs than horse –> fewer thoracic vertebrae (13)
- dorsal spinous process of sacral vertebrae are fused as well as the vertebral bodies (unlike horse)
what is the vertebral formula of the pig
C7 T14-16 L6-7 S4 Cc variable
what is the vertebral formula in the sheep
C7 T13 L6 S5 Cc variable
