Spine Flashcards
Function of the spine
axial skeleton for weight bearing and mobility- adapted for weight transmission in the upright posture
spinal cord protection
How many veterbrae?
33
How many of each segment?
cervical- 7
thoracic- 12
lumbar- 5
sacral 5 fused
coccygeal- 4
Normal curvature of each region
cervical- lordosis
thoracic- kyphosis
lumbar and sacral- lordosis
Abnormal developments of the spine
Scoliosis- lateral concavity
kyphosis- hunchback- excessive thoracic convexity
lordosis- sway back- excessive lumbosacral concavity
Briefly, embryonic origin of spine?
paraxial mesoderm- somites, patterned by transcription factors scubas Hox and PAX genes, form medial sclerotome- endochondral ossification
notochord expresses Shh which induces medial somitic cells to form sclerotome
sclerotome definition
Part of each somite in a vertebrate embryo giving rise to bone or other skeletal tissue
Structure of a typical vertebrae + function
- vertebral body with a somewhat oval shape. Body is covered in strong cortical bone with cancellous bone within.
- pedicle- two short processes made of cortical bone that protrude from the back of the ventral body
- spinal cavity- cavity that contains the spinal cord within the cerebral column
- lamina- two flat pates of bone that extend from the pedicles on either side and join the middle
transverse process- two on each side of the vertebral body where the lamina joins the pedicle. Serve as points of attachment for the inter transverse ligament.
articular process- contain a superior and inferior facet
spinous process- extending cortical bone which project centrally- points dorsally and caudally. serves as a point of attachment for muscles and ligaments
Cervical vertebrae structure
- smallest and lightest vertebrae
- triangular vertebral foramen
- short bifid spinous processes
- two transverse foramen which allows the passage to the vertebral artery and vein
- each transverse foramen has an anterior and posterior tubercle
2 different cervical vertebrae
C1- Atlas C2- axis
Explain structure of atlas
- does not have a spine, instead has a posterior tuberosity
- articulates with the occiput of the head and the axis
- has no vertebral body
- anterior and posterior arch that join two masses
- anterior arch has a facet for articulation with the dens
- posterior arch has groove for vertebral artery and C1 nerve
Explain structure of axis
- anterior odontoid process (dens) that articulates with the anterior facet of the atlas
- everything else the same as normal cervical spine
Two different joints + their functions
Atlanto-occipital joint- allows the skull to move up and down. Two synovial condyloid joints
Atlanto-axial joint- allows the upper neck to twist left and right- synovial pivot joint
What other cervical vertebrae varies?
c7- referred to as vertebrae prominens, as it has a longer spinous process- not usually bifid- easy to palpate
What movements allowed in cervical region of spine?
- quite mobile compared to the thoracic and lumbar regions of the spine
- rotation and lateral flexion
Structure of thoracic vertebrae
- transverse processes have facets to articulate with the head of ribs -c alley transversocostal facet
- near root of pedicle two costal Demi facets- where the rib articulates from one above and below
- small vertebral foramen
- long spine
- heart shaped vertebral body
Attachment of rib to thoracic vertebrae
- all 12 ribs articulate posteriorly with the vertebrae of the spine
- costotransverse joint- tubercle of rib and the transverse costal facet of the corresponding vertebrae
- costovertebral joint- between the head of the rib, superior costal facet of the corresponding vertebrae and the inferior costal facet of the vertebrae above
Which rib is different?
First rib- only one costoverebral joint, as there is no vertebrae above it to provide the inferior costal facet
Movement allowed in thoracic column?
very little movement due to presence of ribs
- small amount of forward and lateral flexion and slight rotation
Structure of lumbar vertebrae
- the largest
- kidney shaped vertebral body
- quadrate spines
- thick pedicles, thick lamina
- interlocking articular facets
Range of movement allowed in lumbar region
Flexion and extension but prevent rotation
Why are lumbar vertebrae this shape?
Largest segments that thus can help support the body and permit movement
Sacral vertebrae structure
- fused
- large surface of articulation with the pelvis
- forms the sacroiliac joint on each side of the pelvis
Structure of sacral iliac joint + function
- joint is covered by two forms of cartilage on either side
- joint surface develops distinct angular orientations as the individual begins walking
- sacral surface as hylaline cartilage
- iliac surface has fibrocartilage
shock absorption - self-locking mechanism helps with the push off phase of walking
Coccyx structure
3 vertebrae fused
articulates superiorly with sacrum
all lack pedicles, laminae and sopinous processes
2 types of joint between vertebrae
synovial between superior and inferior articular processes
- cartilaginous between bodies
Explain structure of the intervertebral disc
Symphysis- secondary cartilaginous
-fibrocartilaginous
- central nucleus pulposus- gelatinous with high water content
- peripheral anulus fibrosis- formed of fibrocartilage - several laminae made up of both type 1 and 2 collagen
Structure of nucleus pulposus
- large vacuolated notochord cells
- small chodnrycte cells
- collagen fibrils
- aggregate attached to hyaluronic acid, keratin sulphate and chondroitin
more negatively charged aggrecan, the more osmosis into the nucleus pulposus
Function of the intervertebral disc
nucleus pulposus
- helps distribute pressure evenly across the disc
- contains loose fibres suspended in mucoprotein gel
stiff laminae help resist compressive forces
what is between the disc and vertebral body?
endplate- contain an osseous and hyaline cartilage component
network of blood vessels through the end plate to the dic
Explain injuries associated with intervertebral discs?
spinal disc herniation- excessive strain or trauma to the spine which injures the disc
- tear in the outer fibrous ring- allows nucleus pulposus to seep out
- sciatica- pain from the lower back going down the leg- often due to slipped disc
Which direction is a disc herniation most common? + why?
postero-lateral
anulus fibrosis is thinnest and not supported by the posterior or anterior longitudinal ligament
posterior direction as posterior longitudinal ligament is thinner than anterior
which vertebrae does it most commonly take place?
lumbar then cervical
In the lumbar region, sciatic nerve is most commonly effected, thus causing sciatica
Which nerve is often effected?
The nerve below the disc
eg. if the disc is between L4 and L5, the nerve compressed will be L5 as the nerve comes out above the vertebrae
What is spinal stenosis?
Abnormal narrowing of the spinal canal that results in pressure on the spinal cord
causes weakness in limbs
often due to osteoarthritis, rheumatoid arthritis and spinal tumours
Different ligaments present + function
supraspinous ligament- along the spines, preventing overextension
interspinous ligament- between spinous processes
inter transverse ligament- between transverse processes
ligamentum flavum- connect ventral parts of the laminae- preserve upright posture
anterior longitudinal ligament- prevents hyperextension and spinal disc herniation
posterior longitudinal ligament- prevents hyeprflexion and spinal disc herniation
ligamentum nuchae- behind the cranium, keeps us upright and the spine in an extended position- continuous with the supraspinous ligament
transverse ligament of atlas- thick strong band that arches across the ring of the atlas and retain the odontoid process in place
Spinal cord in relation to spine structure
- occupies vertebral canal
- terminates lower border in L1 in adult or L3 in child
- cervical and lumbar enlargements
- cord tapers to conus medullar is
- nerve roots continue as caudal equina
- nerve roots before leave between intervertebral foramen composed of the superior and inferior vertebrae
Hangman fracture explained
fracture of the dens caused by an extreme force on the upper vertebrae
