the spine and spinal structures

Question 1

the vertebral column

Answer 1

• Consists of 33 vertically stack vertebrae of various sizes
• Average spine is between 72 and 75cm
• 25% of the length of the spine is the intervertebral discs
• Spine determines about 40% of a person’s height so any reduction in vertebral length will affect this
• The cervical and lumbar regions have an anterior curve (anteriorly convex)
• The thoracic and sacral regions have a posterior curve (anteriorly concave)
• In the spinal column there are 4 distinct curves which are essential is spine’s ability to handle load and absorb shock

Question 2

cervical

Answer 2

7 individual vertebrae
anterior convexity
has to support weight of head and assist support of shoulder complex
has greatest mobility in whole spinal column

Question 3

thoracic

Answer 3

12 vertebrae
span entire upper back
its posterior convexity houses many of vital organs
attached to each thoracic vertebrae is a rib, 10 of which span anteriorly and superiorly to the sternum via the costal cartilage
the lower 2 ribs provide protection posteriorly and laterally but do not articulate with the costal cartilage = ‘floating ribs’

Question 4

lumbar

Answer 4

5 vertebrae
anterior convexity
the curvature ranges from 25-30 degrees
in a healthy spine this curvature is dramatically affected by the degree of pelvic tilt.
a posterior pelvic tilt reduces the lumbar curvature creating a flat back posture
an anterior pelvic tilt exaggerates the lumbar curvature and contributes to a lordotic posture

Question 5

sacrum

Answer 5

5 vertebrae fused together to form triangular plate of bone that narrows inferiorly
this structure provides attachment for several muscles and distributes forces from upper to lower body

Question 6

coccyx

Answer 6

4 vertebrae fused together to form a single bone, or in some cases, two pieces of bone
this bone curves anteriorly and is often referred to as the tailbone.

Question 7

atlas and axis

Answer 7

rotation takes place at the joint between the cranium and the atlas (first cervical vertebrae)
flexion and extension occurs through the joints of the spinal vertebrae apart form the sacrum and coccyx, which are fused
lateral flexion occurs through the lumbar vertebrae while rotation occurs primarily through the thoracic vertebrae

Question 8

the ribs

Answer 8

there are 12 pairs of ribs that can each be described as ‘curved flat bones’
ribs are connected to the thoracic vertebrae posteriorly by cartilaginous joints
the upper 7 ribs are ‘true ribs’ and attach directly to the sternum anteriorly via the costal cartilage
the lower 5 pairs of ribs however are known as ‘false ribs’ because they do not join with the sternum directly - instead they connect to the 7th rib
11th and 12th = ‘floating ribs’

Question 9

intervertebral discs

Answer 9

these are located between the vertebrae in the cervical, lumbar and thoracic regions of the spine
2 primary functions:
1) assist in the production of movement between adjacent vertebrae
2) the transfer and disperse load from one vertebra to next - a process known as ‘load transference’
each disc has two major components = the nucleus pulposus and annulus fibrosus

Question 10

nucleus pulposus

Answer 10

situated towards centre of the disc when spine is in neutral
nucleus is composed of collagen, water and glucose to give it gel like texture

Question 11

annulus fibrosus

Answer 11

the fluid component of the disc that surrounds the nucleus
while there is no distinct border between nucleus and the annulus, the annulus becomes more prominent towards outer surfaces of the disc

Question 12

the end plate

Answer 12

a deformable plate of cartilage on upper and lower surfaces of the vertebral body
immediately superior and inferior to the intervertebral disc.
when spine is loaded, the end plate deforms and bulges into the vertebral body absorbing much of the load.
intervertebral discs behave as hydrostatic structures allowing only 6 degrees of motion at each vertebra

Question 13

slipped disc

Answer 13

the discs greatest loading position is from a neutral position
when load is applied to the disc during a flexed or extended posture, the nucleus migrates in the opposite direction and causes the disc to sag/bulge
if this occurs repeatedly or spine is placed under heavy load, the intervertebral discs can become herniated = ‘slipped disc’

Question 14

neural arch canal

Answer 14

• Vertebral canal
• Formed by 2 thick processes that project posteriorly and laterally from vertebral body
• The vertebral foramen is located between neural arch and vertebral body
• This houses the spinal cord, fat, connective tissue and blood vessels
• It also includes lateral spaces between inferior and superior vertebrae to allow nerves to branch off from spinal cord.
• Pedicles are on the lateral surface of the neural arch – they are not as deep as vertebral body
• Pedicles allow the nerves and spinal blood vessels to leave the vertebral canal in between each intervertebral disc.

Question 15

spinal ligaments

Answer 15

• As the spine flexes, extends and/or rotates, the spinal ligaments are stressed and stretched
• Spinal ligaments are more elastic than other ligaments so they are placed under tension to protect other spinal structures
• The more the spine deviates from a neutral position, the more the spinal ligaments contribute to spinal stability
• They resist movement opposite to the direction they are positioned and their fibres run
• The structure of the spine allows for larger ranges of flexion than extension – the anterior spinal ligaments are not as active in resisting extension as the posterior ligaments are in resisting flexion
• Spinal ligaments are saturated with mechanoreceptors that provide sensory information about volume of deformation and stretching within the ligament = people can feel their spinal position without seeing it

Question 16

the processes of each vertebra

Answer 16

each vertebra has 7 total processes that interact to create the facet joints.

• 2 transverse processes which span laterally and posteriorly
• 2 mamillary processes which span superiorly and posteriorly
• 2 inferior articular facets which span posteriorly
• 1 spinous process which projects posteriorly