Spine

Question 1

Function of the spine

Answer 1

axial skeleton for weight bearing and mobility- adapted for weight transmission in the upright posture

spinal cord protection

Question 2

How many veterbrae?

Answer 2

33

Question 3

How many of each segment?

Answer 3

cervical- 7

thoracic- 12

lumbar- 5

sacral 5 fused

coccygeal- 4

Question 4

Normal curvature of each region

Answer 4

cervical- lordosis

thoracic- kyphosis

lumbar and sacral- lordosis

Question 5

Abnormal developments of the spine

Answer 5

Scoliosis- lateral concavity

kyphosis- hunchback- excessive thoracic convexity

lordosis- sway back- excessive lumbosacral concavity

Question 6

Briefly, embryonic origin of spine?

Answer 6

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

Question 7

sclerotome definition

Answer 7

Part of each somite in a vertebrate embryo giving rise to bone or other skeletal tissue

Question 8

Structure of a typical vertebrae + function

Answer 8

• 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

Question 9

Cervical vertebrae structure

Answer 9

• 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

Question 10

2 different cervical vertebrae

Answer 10

C1- Atlas C2- axis

Question 11

Explain structure of atlas

Answer 11

• 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

Question 12

Explain structure of axis

Answer 12

• anterior odontoid process (dens) that articulates with the anterior facet of the atlas
• everything else the same as normal cervical spine

Question 13

Two different joints + their functions

Answer 13

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

Question 14

What other cervical vertebrae varies?

Answer 14

c7- referred to as vertebrae prominens, as it has a longer spinous process- not usually bifid- easy to palpate

Question 15

What movements allowed in cervical region of spine?

Answer 15

• quite mobile compared to the thoracic and lumbar regions of the spine
• rotation and lateral flexion

Question 16

Structure of thoracic vertebrae

Answer 16

• 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

Question 17

Attachment of rib to thoracic vertebrae

Answer 17

• 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

Question 18

Which rib is different?

Answer 18

First rib- only one costoverebral joint, as there is no vertebrae above it to provide the inferior costal facet

Question 19

Movement allowed in thoracic column?

Answer 19

very little movement due to presence of ribs

• small amount of forward and lateral flexion and slight rotation

Question 20

Structure of lumbar vertebrae

Answer 20

• the largest
• kidney shaped vertebral body
• quadrate spines
• thick pedicles, thick lamina
• interlocking articular facets

Question 21

Range of movement allowed in lumbar region

Answer 21

Flexion and extension but prevent rotation

Question 22

Why are lumbar vertebrae this shape?

Answer 22

Largest segments that thus can help support the body and permit movement

Question 23

Sacral vertebrae structure

Answer 23

• fused
• large surface of articulation with the pelvis
• forms the sacroiliac joint on each side of the pelvis

Question 24

Structure of sacral iliac joint + function

Answer 24

• 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

Question 25

Coccyx structure

Answer 25

3 vertebrae fused articulates superiorly with sacrum all lack pedicles, laminae and sopinous processes

Question 26

2 types of joint between vertebrae

Answer 26

synovial between superior and inferior articular processes - cartilaginous between bodies

Question 27

Explain structure of the intervertebral disc

Answer 27

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

Question 28

Structure of nucleus pulposus

Answer 28

- 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

Question 29

Function of the intervertebral disc

Answer 29

nucleus pulposus - helps distribute pressure evenly across the disc - contains loose fibres suspended in mucoprotein gel stiff laminae help resist compressive forces

Question 30

what is between the disc and vertebral body?

Answer 30

endplate- contain an osseous and hyaline cartilage component network of blood vessels through the end plate to the dic

Question 31

Explain injuries associated with intervertebral discs?

Answer 31

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

Question 32

Which direction is a disc herniation most common? + why?

Answer 32

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

Question 33

which vertebrae does it most commonly take place?

Answer 33

lumbar then cervical In the lumbar region, sciatic nerve is most commonly effected, thus causing sciatica

Question 34

Which nerve is often effected?

Answer 34

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

Question 35

What is spinal stenosis?

Answer 35

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

Question 36

Different ligaments present + function

Answer 36

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

Question 37

Spinal cord in relation to spine structure

Answer 37

- 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

Question 38

Hangman fracture explained

Answer 38

fracture of the dens caused by an extreme force on the upper vertebrae