Vertebral column - prac and KC

Question 1

List common features of all vertebrae

Answer 1

Common features to all vertebrae include (from anterior to posterior):
- vertebral body and foramen
- pedicle
- transverse process
- articular processes
- lamina
- spinous process

Question 2

Describe the features of cervical vertebrae

Answer 2

Cervical vertebrae
There are seven cervical vertebrae. They are the smallest of the vertebrae.

They are characterised by:
- a bifid spinous process (with exceptions…C7 may not bifurcate)
- transverse foramina, in each transverse process. Through here, vertebral arteries travel to the brain
- **a triangular vertebral foramen
- **articular processes are ‘open’ ( ..allows x movement. See physiopedia)

Question 3

Describe the features of thoracic vertebrae

Answer 3

Thoracic vertebrae
There are twelve vertebrae are medium-sized, and increase in size inferiorly.
There are several features that distinguish thoracic vertebrae:
- **spinous processes are oriented obliquely, inferiorly and posteriorly
- **articular processes are ‘reading the book’ ( ..allows x movement. See physiopedia)
- **circular vertebral foramen
- demi facets, one superior and one inferior, on either end of the vertebral body
- the demi facets articulate with the heads of two different ribs to form the costovertebral joints-
– e.g. at T2, the head of rib 2 articulates with the superior demi facet of T2, and the head of rib 3 articulates with the inferior demi facet of T2
- costal facet on the transverse process which articulates with the shaft of the rib of the same number e.g. costal facet of T2 articulates with shaft of rib 2

Question 4

Describe the lumbar vertebrae

Answer 4

Lumbar vertebrae
There are five lumbar vertebrae. They have the biggest vertebral bodies.
Special characteristics include:
- kidney shaped vertebral bodies
- **triangle shaped vertebral foramen
- shorter spinous processes c.v. thoracic vertebrae and do not extend inferiorly
- **articular processes ‘close the book’ ( ..allows x movement. See physiopedia)

Question 5

Describe atlas

Answer 5

Atlas
or C1. It articulates with the occiput and C2.

It has NO:
- vertebral body
- spinous process

It has:
- lateral masses, with oval-shaped superior articular facets (articulating with occipital condyles) and inferior articular facets (articulating with C2) connected by…
- anterior arch, which has a facet for articulating with the dens of the axis, which is secured by the transverse ligament of the atlas (see below)
- posterior arch, which has a groove for the vertebral artery and C1 spinal nerve

Question 6

Describe axis

Answer 6

Axis
or C2, which articulates with C1 and C3.
Its most characteristic feature is the dens, in addition to the general features of the typical cervical vertebrae.

Question 7

Describe the features of the sacrum

Answer 7

The sacrum comprises about 5 bones that fuse in adolescence.
There are several key features on the anterior side and the posterior side (ALL ASSESSABLE):
##### Anterior side
- auricular surface
- ventral sacral foramina
- sacral ala
- sacral promontory
also transverse ridge
##### Posterior side
- superior articular facet
- sacral canal
- median sacral crest (also lateral or intermediate)
- sacral hiatus
- dorsal sacral foramina

also sacral corni

Question 8

Describe facet joints

Answer 8

Facet (zygapophysial) joints
Facet joints are synovial plane joints, between the superior articular facets of the inferior vertebra and the inferior articular facets of the superior vertebra.
It works to guide and limit movements between vertebrae.

As synovial plane joints, the facet joints are composed of:
- hyaline articular cartilage which lines the facet surfaces of the superior and inferior articular processes
- synovial joint cavity between the articular surfaces which contains synovial fluid
- fibrous capsule, surrounding the joint, and lined by synovial membrane
- except for the anterior fibrous capsule, which is formed by the ligamentum flavum

The articular surfaces glide in a multitude of directions, which collectively produce movement in the spine of all planes:
- flexion and extension
- right and left lateral flexion
- right and left rotation

Question 9

Describe interbody joints

Answer 9

Interbody joints sit between the vertebral bodies and intervertebral discs.
It is a cartilaginous symphysis.
Interbody joints connect the vertebrae anteriorly, to enable movement.
The disc is also involved in:
- weight-bearing
- shock absorption
- load distribution

Each intervertebral disc is composed of:
- an outer annulus fibrosus, which is composed of concentric sheet-like layers (lamellae) of fibrocartilage
- the annulus functions to resist the tensile and compressive stresses the intervertebral disc is subjected to
- an inner nucleus pulposus which contains loose fibres suspended in a mucoprotein gel, which functions to distribute compressive forces evenly across the disc and acts as a shock absorber
- note: vertebral endplates sit between vertebral bodies and intervertebral discs. They are composed of
- an inner cartilaginous layer that fuses with the disc
- an outer layer that attaches to the vertebra

~An exception to this is the C1-C2 or atlanto-axial joint, as it does not have an intervertebral disc, and only has facet joints~

Question 10

Describe the atlanto-axial joints

Answer 10

The dens and anterior arch together comprise the median atlanto-axial joint.
The inferior articular facets of the atlas and the superior articular facts of the axis form the lateral atlanto-axial joints.

Atlanto-axial joints provide the majority of cervical spine rotation and some flexion/extension.
Lateral and median joints work together to provide cervical rotation, flexion and extension.

Question 11

Describe atlanto-occipital joints

Answer 11

Atlanto-occipital joints
are another specialised joint that involves the atypical C1 vertebra.
It is a synovial condyloid joint.
It permits flexion and extension of the head and neck (as well as a small amount of lateral flexion).

Note: the atlanto-axial and atlanto-occipital joints are not strictly biaxial…because of ligaments.

Question 12

Describe the anterior and posterior longitudinal ligaments

Answer 12

• the anterior longitudinal ligament which connects the anterior vertebral bodies and intervertebral discs up to the anterior tubercle of C1. The anterior atlanto-occipital membrane then connects the anterior tubercle of C1 to the occiput.
  
  • the posterior longitudinal ligament which connects the posterior aspects of the vertebral bodies and intervertebral discs up to the C2 vertebral body. The tectorial membrane then connects C2 to the occiput

appear as dark lines on MRI

Question 13

List and describe the other three ligaments of the spine

Answer 13

• the ligamentum flavum which is composed of elastic tissue and connects the laminae of adjacent vertebrae up to the posterior arch of C1. The posterior atlanto-occipital membrane connects the posterior arch of C1 and the occiput
  
  • the interspinous ligament which connects adjacent spinous processes
  • the supraspinous ligament which connects the tips of the spinous processes up to the C7 spinous process. It forms astrong broad ligament extending between theC7 spinous process and external occipital protuberance know as the ligamentum nuchaeand isan important site of muscle attachment

Question 14

List some other specialised ligaments of the upper cervical spine

Answer 14

• transverse ligament, which is a strong thick horizontal band that passesbehind the dens of C2 as itattaches betweenthe lateral masses of C1.
  
  • It is essential to maintaining the stability of the median atlanto-axial joint by preventing posterior displacement of the dens and anterior displacement of C1.
• Alar ligaments, which extend betweenthe sides of the dens andthe lateral margins of the foramen magnum.
  
  • The alar ligaments prevent excessive rotation of the atlanto-axial joints.

Question 15

Describe the composition of the vertebral ligaments

Answer 15

All of the ligaments are primarily composed of collagen except ligamentum flavum which is composed primarily of elastin giving ita yellow colour.It resists excessive separation of the laminae during flexion and it’s elasticity prevents it bucklinginto the vertebralcanal during extension thus protecting the spinal cord from compression.The lateral partof the ligament contributes to the anterior fibrous capsule of the facet joint.

Question 16

Describe the movements that are limited by the ligaments of the spine

TBC

Answer 16

• anterior longitudinal ligament = limits hyperextension of spine
  
  • posterior longitudinal ligament = limits hyperflexion of spine; prevents posterior herniation of IVD
  • ligamentum flavum = limits separation of laminae to prevent hyperflexion of spine
  • interspinous ligament = prevents separation of spinous processes during flexion; resisting hyperflexion
  • supraspinatus = prevents separation of spinous processes during flexion; resisting hyperflexion
  • transverse = resists separation of vertebral bodies?, in order to resist or limit flexion

Question 17

Describe the purpose of the curvature of the spine

Answer 17

Posteriorly or anteriorly, the spinal cord appears more or less straight.
Seen laterally, it is curved. Four curves for the four sections of the vertebral column.
The curves work as a shock-absorber, as well as aiding weight distribution.

Question 18

Describe the function and innervation of layer 1 posterior muscles

Answer 18

• latissimus dorsi
  
  • function
    
    • glenohumeral joint: extension, adduction, and medial rotation
  • innervation: thoracodorsal nerve (C6 - C8 ventral rami)
  • trapezius
    
    • function
      
      • scapula: elevation, depression, rotation and retraction
      • head and neck: extension and lateral flexion
    • innervation: CN XI, and C3-4 ventral rami

Question 19

Describe the function and innervation of layer 2 posterior muscles

Answer 19

• levator scapulae
  
  • function
    
    • scapula: elevation and rotation
    • neck: extension and lateral flexion
  • innervation
    
    • dorsal scapular nerve (C4,5); C3-C4 ventral rami
• rhomboids
  
  • function
    
    • scapula: retraction
  • innervation
    
    • dorsal scapular nerve (C4,5)

Question 20

Describe function and innervation of layer 4 posterior muscles

Answer 20

• splenius capitis and cervicis
  
  • function
    
    • head and neck: extension, lateral flexion and ipsilateral rotation
  • innervation
    
    • dorsal rami (capitis: C3 and C4?, cervicis: ‘lower cervical nerves’; c5-8?)

Question 21

Describe function and innervation of layer 5 posterior muscles

Answer 21

• erector spinae (iliocostalis, longissimus, spinalis)
  
  • function
    
    • spine: extension and lateral flexion
  • innervation
    
    • dorsal rami (C1-L5)

Question 22

Describe function and innervation of layers 1 and 2 anterior muscles

Answer 22

Layer 1
- sternocleidomastoid
- function
- head and neck: flexion, lateral flexion and contralateral rotation
- atlanto-occipital joints: extension
- innervation
- CN XI; C2-3/4 ventral rami
##### Layer 2
- scalenes (anterior, middle and posterior)
- function
- neck: flexion, lateral flexion and rotation
- innervation
- ventral rami (C3-8?)

Question 23

Describe the function and innervation of lumbar spine anterior muscles

Answer 23

Superficial lumbar
- rectus abdominis, external oblique, internal oblique and transversus abdominis
- function: flexion, lateral flexion and rotation
- innervation: ventral rami

Deep lumbar
- psoas major
- function
- lumbar spine: flexion and lateral flexion
- hip joint: flexion
- innervation: ventral rami (L1-4, plus femoral nerve branches?)
- quadratus lumborum
- function
- lumbar spine: lateral flexion
- innervation: ventral rami (T14-L4)

Question 24

Describe the borders of the vertebral canal

Answer 24

It is bound:
- anteriorly by the vertebral bodies, IVDs and posterior longitudinal ligament
- laterally by the pedicles and laminae
- posteriorly by the laminae, spinous processes and ligamentum flavum.

Question 25

List the contents of the vertebral canal

Answer 25

• epidural space with IVVP and epidural fat
• IVVP
• meninges (dura, arachnoid, and pia)
• spinal cord

Question 26

Describe epidural space

Answer 26

• lies immediately beneath the bony and ligamentous elements forming the vertebral canal and contains the internal vertebral venous plexus embedded in the epidural adipose tissue (epidural fat) and areolar tissue.
  
  • # clinicallyrelevant : In an “epidural”, regional anaesthesia is produced by injecting anaesthetic agent between the spinous processes and beneath ligamentum flavum into the epidural space.

Question 27

Describe IVVP

Answer 27

• located beneath the bony elements of the vertebral foramina embedded in the epidural adipose tissue.
  
  • It consists of many interconnected longitudinal channels that run along the posterior and anterior aspects of the vertebral canal.
  • Also known as the epidural venous plexus, extradural venous plexus and Batson’s channels
  • # clinicallyrelevant : the potential route for the spread of infection and cancer
  • There are also arteries and lymphatic vessels present with the veins in the epidural fat.

Question 28

Describe the meninges

Answer 28

• meninges, which collectively lie beneath he epidural venous plexus and epidural adipose tissue and form a protective layer around the spinal cord
  
  • dura, which is separated from
  • arachnoid by a potential subdural space. This contains a thin film of fluid to moisten the apposing membrane surfaces. Both dura and arachnoid extend to S2 level
    
    • subarachnoid spacspe separates the arachnoid and pia
      
      • its is filled with CSF, arteries supplying spinal cord, and arachnoid trabeculae ^[connecting arachnoid and dura mater to pia mater]
      • note from L2 to S2, subarachnoid space is termed lumbar cistern and contains CSF, cauda equina and filum terminale
        pia, which extends inferior to conus medullaris, as the filum terminale, which pierces the dural sac
    • denticulate ligaments, composed of pia mater, attach along the lateral surface of the dura, midway between dorsal and ventral nerve roots, and onto the periosteum from foramen magnum all the way to T12/L1

Question 29

Describe the spinal cord

Answer 29

• Begins at the level of the foramen magnum of the occipital bone of the skull, where it is continuous with the medulla oblongata of the brainstem, and extends to the L1/2 IVD where it tapers and ends as the conus medullaris.
  - During development the spinal cord extends the length of the vertebral column, however, while the vertebral column continues to develop in length, the spinal cord lags behind so that it comes to occupy the upper two-thirds of the spinal canal.
  - At birth the cord ends at approximately the level of the L3 vertebra. In adults continued greater growth of the vertebral column brings the spinal cord to end at the S1/S2 IVD.
  - The spinal cord segments do not correspond with the vertebral levels i.e. the cord segments are not necessarily located at the same level as their corresponding vertebrae.
  - Generally, cervical cord segments and cervical vertebrae correspond closely to one another but the remaining segments do not.
  - The length of the segments changes such that the L1 through coccygeal cord segments are surrounded by vertebrae T9 to L1

• # clinicallyrelevant : A patient with a fractured L1 vertebra does not experience the same lower limb signs and symptoms as a patient with a fractured T10 vertebra…

     - because a T10 fracture injures upper lumbar segments and an L1 fracture injures the lower sacral and coccygeal segments.  

  • Narrowing of the anteroposterior or transverse diameter of the vertebral canal results in spinal (vertebral) canal stenosis and may result in compromise of the spinal cord.
  • A variety of pathologic space-occupying lesions may result in stenosis including posterior IVD protrusion, fracture, spinal cord tumour, facet joint hypertrophy, PLL ossification and buckling of ligamentum flavum.

Question 30

Describe the borders of the intervertebral foramen

Answer 30

• Left and right intervertebral foramina (IVFs) are located between all adjacent vertebrae from C2 to sacrum and lie posterior to the vertebral bodies between the pedicles.
  
  • Thus superiorly (roof) and inferiorly (floor) the IVFs are bound by the pedicle of the vertebra above and below, respectively.
  • The anterior boundary consists of the bodies of the vertebra above and below and the intervening IVD.
  • The posterior wall is composed of the vertebral laminae and zygapophysial joints.
  • Note: the sacrum has ventral and dorsal sacral foramina (instead of intervertebral foramina) for the ventral and dorsal rami of the sacral spinal nerves, respectively, to pass out from the cauda equina in the sacral canal.
  • The S5 spinal nerves and the coccygeal nerve exit the sacral canal via the sacral hiatus with the filum terminale.

- The size of the IVF changes with spinal movements.
- It becomes larger in spinal flexion and smaller in spinal extension.
- A decrease in IVD height can decrease the IVF dimensions

Question 31

List the contents of the intervertebral foramen

Answer 31

There are five major contents of the intervertebral foramina:
communicating, or intervertebral, veins,
branches of the segmental arteries,
lymphatic channel/s,
adipose tissue that surrounds all structure within the IVF
AND

Question 32

Describe the spinal nerves

Answer 32

There are 31 pairs of spinal nerves.

They are named according to the vertebra to which they are related
- cervical spinal nerve are named according to the vertebra below them (except for C8, which lies above v-T1)
- other spinal nerves are named for the vertebra that lies above them
- a disc herniation occurring at the level of the C3/C4 IVD usually affects the exiting C4 spinal nerve.
- A disc protrusion of the T3/T4 IVD normally affects the T3 spinal nerve.
- In the lumbar spine the spinal nerve roots make a dramatic lateral turn around the pedicle of the superior vertebra of the IVF and thus cross the IVD above their level of exit and not the IVD of the same level.
- Thus a posterior L3/L4 IVD protrusion is most likely to affect the L4 spinal nerve (exits the L4/L5 IVF) rather than the L3 spinal nerve (exits the L3/L4 IVF).

As the spinal nerve exits the IVF it divides into a dorsal ramus and a ventral ramus.
- ventral rami
- cervical
- cervical plexus (C1 - C4 ventral rami)
- innervates the anterior neck muscles, diaphragm and skin of anterolateral neck
- brachial plexus (C5 - C8 plus T1 ventral rami)
- innervates musculature and joints of the pectoral girdle and upper limb and skin of the upper limb
- thoracic intercostal nerves (T1-T12 ventral rami)
- innervates intercostal and anterior abdominal muscles and overlying skin
- lumbar
- lumbrosacral plexus (T12/L1 to S3 ventral rami)
- innervation of muscles of lower anterolateral abdominal wall, skin of groin, lateral thigh,, external genitalia, muscles and skin of lower limb
- dorsal rami
- Remain independent and do not form plexuses. The dorsal rami course posteriorly to innervate the posterior structures of the trunk including overlying skin, muscles, bones, ligaments and meninges and posterior vertebral canal structures.