Spine/Back Flashcards
(58 cards)
How many vertebra and spinal nerves are there?
C7 - 8 nerves
T12 - 12 nerves
L5 - 5 nerves
S5 - 5 nerves
C4 - 1 nerve
~33 bones in total & 31 pairs of spinal nerves
What are the functions of the spine?
- Protection of spinal cord
- Movement
- Axis
- Supports
What are the key features of a vertebral body?
- Body (gets larger the lower down the spine) lined by hyaline cartilage superiorly/inferiorly
- Seperated by cartilaginous IVD
- Vertebral arch
- Vertebral foramen
- Spinous processes
- Transverse processes
- Pedicles (body to transverse process)
- Lamina (connects spinous & transverse process)
- Articular processes to connect to sup/inf vertebral bodies
Explain the anatomy of the IVD. How do they prolapse?
Secondary fibrocartilaginous joint
Inner nucleus pulposus and outer annular fibrosus
Movements: FL/EX, lateral FL & axial rotation
Herniates postero-laterally due to decrease in size of post. longitudinal ligament in lower back causing irritation to lower spinal root - a central prolapse will cause cauda equina
How do the cervical vertebra differ?
Short bifid spinous process EXCEPT:
C1 has no spinous process
C2 is very thick
C7s is very long and may not bifurcate
So cannot be felt as attached to nuchal ligament
Transverse foramina for vertebral artery (below C6 and at C7 it is smaller for vein as the artery comes in at C6)
Triangular vertebral foramen
Specialised:
C1 (atlas): no body, allows flexion of head so facet for occipital condyle
C2 (axis): body forms odontoid peg/dens for rotation of head + facet for attachment to alar ligament
How do the thoracic vertebra differ?
2 demi-facets on each superiorly/inferiorly of vertebral bodies to articulate with head of ribs
Costal facet on transverse processes for articulation with rib shaft
Spinous processes are postero-inferiorly directed
Circular vertebral foramen
For example, the head of Rib 2 articulates with the inferior demi facet of T1 and the superior demi facet of T2, while the shaft of Rib 2 articulates with the costal facets of T2
How do the lumbar vertebra differ?
Large kidney shaped vertebral bodies
Triangular shaped vertebral foramen
Shorter spinous processes and do not extend inferiorly
How do sacrum and coccyx differ?
Fused vertebrae
Sacrum is formed of 5 and is an inverted triangle with facets for articulation with ilium at SIJ either side
Coccyx is formed of 4 and is small articulating with apex of sacrum with absent vertebral canal & arches
What are the joints & ligaments of the vertebral column?
Joints:
1. Superior articular facets: articulate with vertebra above
2. Inferior articular facets: articulate with vertebra below
3. IVD: vertebral body articulation
4. Atlano-axial joint: synovial pivot
Ligaments:
1. Ant. longitudinal: prevents hyperextension
2. Post. longitudinal: prevents hyperflexion -> tectorial membrane at top
3. Ligamentum flavum: between lamina
4. Interspinous: join spinous processes
5. Supraspinous: join tips of spinous processes
6. Transverse ligament: between transverse processes
7. Alar ligaments, transverse atlantal & apical odontoid all attach to odontoid at superior end
What level does the spinal cord terminate? Where do you perform LP and what are the layers?
L2 in adults forming fcauda equina (L2-S5) conus medullaris (S1-5) then filum terminale
L3 in children
Dural sac ends at S2
LP @ supracristal plane (L4-5) going through skin, subcut fat, fascia, supraspinous ligament, interspinous, ligamentum flavum, epidural space, dura, subdural space, arachnoid mater & subarachnoid space w/ CSF
What are the 2 enlargements of the spinal cord?
Cervical = C4-T1 where brachial plexus starts
Lumbar = T11-L1 where lumbosacral plexus arises
What is the anatomy of the spinal nerves?
Mixed nerves forming PNS
Begin as anterior (motor) root and posterior (sensory) root uniting at intervertebral foramina to form a single nerve
Leaves the vertebral canal and splits into posterior and anterior rami to supply back and then everything else respectively
What is the blood supply & venous drainage to the spinal cord?
1x anterior spinal artery
2x posterior spinal artery
(From vertebral arteries)
Small ant/post segmental medullary arteries entering via nerve roots - largest is artery of Adamkiewicz supplying inferior 2/3rd of cord (inf. intercostal/upper lumbar arteries)
Venous drainage is via radicular veins -> 3x anterior spinal and 3x posterior spinal veins -> internal ant/post vertebral plexuses (run length ant/post to dura)* -> DVCs (internal) + systemic segmental veins
*note external plexuses anterior one is small system around body whereas posterior is extensive system around processes
Please briefly describe the anatomy of the muscles of the back.
Superficial layer: shoulder movements
1. Trapezius: from skull, ligamentum nuchae & spinous processes of C7-T12 attaching to clavicle, acromion & scapula spine (CNXI) - elevates scapula + rotates it during abduction
2. Lat dorsi: from spinous process T6-T12 , thoracolumbar fascia, iliac crest & inferior 3 ribs to intertubercular groove of humerus (thoracodorsal n) - extends/adducts + MR of UL
3. Levator scapulae: transverse process of C1-4 to medial scapula border (dorsal scapular n) - scapula elevation
4. Rhomboids major: spinous process T2-5 to medial scapula border (dorsal scapular n) - retracts/rotates scapula
5. Rhomboid minor: from spinous processes C7-T1 attaching to medial scapula border (dorsal scapular n) - retractes/rotates scapula
Intermediate: thoracic cage movements (intercostal nerves)
1. Serratus posterior superior: inferolateral direction of fibres elevating ribs 2-5
2. Serratus posterior inferior: superolateral direction of fibres depressing ribs 9-12
Deep/intrinsic: vertebral column movements
1. Superficial (spinotransversales): splenius capitis (post. rami of C3-4) & cervicis (post. rami of lower C nerves) - rotate head/EX if BL
2. Intermediate/erector spinae: iliocostalis, longissimus & spinalis - arise from lower T/L vertebra, sacrum, post. illiac crest & sacroilliac/supraspinous ligaments causing lat. flexion or extension if BL (post. rami of spinal nerves)
3. Deep (transversospinales): semispinalis, multifidus & rotatores (post. rami of spinal nerves)
=~12
What structures pass through intervertebral foramen?
- Root of each spinal nerve
- Dorsal root ganglion
- Spinal artery of segmental a
- Communicating veins between internal/external plexuses
- Recurrent meningeal nerves
- Transforaminal ligaments
What does the scottie dog represent?
Nose = transverse process
Ear = superior articular process
Eye = pedicle
Neck = pars interarticularis (incomplete in spondylolysis = stress #)
Whats in the epidural space?
Lymphatics
Spinal nerve roots
Loose connective tissue & fatty tissue
Small arteries
Internal vertebral venous plexus
What tumours metastasize to the spine and via what route?
Breast, lung, thyroid, kidney & prostate
Routes:
1. If primary via arterial system
2. Retrograde through batsons plexus: valveless vein network connecting deep pelvic veins draining bladder, prostate + rectum to internal vertebral venous plexus
3. Direct invasion through intervertebral foramina
What structures are found at C6?
Arch of cricoid (laryngeal prominence @ C4-5)
Vertebral artery enters transversarium foramen
Termination of pharynx + beginning of oesophagus
Termination of larynx & beginning of trachea
Middle thyroid VEIN emerging from thyroid gland
Inferior thyroid ARTERY entering thyroid gland
Intermediate tendon of omohyoid crosses carotid sheath
What happens at C3-4?
Hyoid bone @ C3
CCA bifurcation @ upper margin of thyroid cartilage
What are the different spinal tracts?
Ascending:
1. Dorsal column (FC UL & FG LL): fine touch, vibration & proprioception made up of 1st order (synapse in medulla where they decussate), 2nd order (synapse in thalamus) & third order neurons (to primary sensory cortex)
2. Ant. spinal thalamic: crude touch & pressure - travel same pathway but decussate 1-2 levels above entering spinal cord
3. Lat. spinal thalamic: pain/temp - “””” pain is sensed via free nerve endings in skin (C fibres = dull ache & A-delta fibres = fast/sharp)
4. Spinocerebellar: unconscious proprioception - all stay ipsilateral
Descending:
Pyramidal tracts
1. Corticospinal: muscles of body - begin in cortex (UMN) and descend via IC of BG -> lateral tract decussates in medulla but ant. tract decussates + terminate in cervical/upper thoracic segments - LMN once exit spinal cord
2. Corticobulbar: head/neck muscles B/L innervation except for CNVII (contralateral on lower 1/2 of face) & CNXII (contralteral)
Extra-pyramidal tracts
3. Vestibulospinal: balance/posture remaining ipsilateral
4. Reticulospinal: voluntary movement + muscle tone
5. Rubrospinal: C/L innervation of fine hand movements
6. Tectospinal: decussate in midbrain & control head movements w/ relation to visual stimuli
What is the difference between a UMN and LMN?
UMN: hypertonia, hyper-reflexia, clonus, babinski sign (extension of toe) + spastic paralysis/weakness e.g. CVA
LMN: hypotonia, hypo-reflexia, fasciculations & flaccid paralysis/weakness e.g. cauda equina or bells palsy
Briefly describe the ANS.
PS = rest/digest
Components:
1. Pre-ganglionic: long, myelinated & release ACh - exit CNS either at CN nuclei in brainstem III , VII , IX & X or sacral spinal nerves S2-4 (form pelvis sphlanchnic nerves)
2. Peripheral ganglia: neuronal cell bodies where synapse occurs close to structure they innervate - ciliary, SM, pterygopalatine & otic
3. Post-ganglionic fibres to effector organs: short, unmyelinated & release ACh
Sympathetic = flight/fight
Components:
1. Pre-ganglionic neurons: originate in thoracic/lumbar segments of spinal cord & are short, unmyelinated + release ACh -> exit cord via ant. spinal nerves passing through white ramus communicans to enter sympathetic trunk where they may:
- Synapse with post-ganglionic neurons at this level
- Ascend/descend within chain to synapse at other level
- Pass through chain w/o synapsing (later will synapse at prevertebral ganglion or adrenal medulla = sphlanchnic nerves)
2. Peripheral ganglia: sympathetic chain either side of vertebral column or prevertebral ganglia around major abdominal aorta branches coeliac, SMA + IMA
- Sympathetic chain = 22 pairs of interconnected cell bodies from skull base to coccyx -> Cx3 (sup/mid/inf), 11-12T, 4L, 5S & 1C
- Prevertebral ganglia supplied by sphlanchnic nerves - coeliac (T5-9 via greater sphlanchnic n), SMA (T10-11 via lesser sphlanchnic n) & IMA (T12 via least sphlanhnic n)
- Adrenal medulla: modified sympathetic ganglion with fibres synapsing directly here to allow it to secrete A/NA
3. Post-ganglionic fibres: long & unmyelinated releasing NA travelling to target via named nerves with blood vessels or within autonomic plexi
What are the common organisms causing osteomyelitis? What is the most common causes?
S. Aureus
Enterobacter species
GAS
Salmonella is pathognomic in SCD patients
Causes:
In adults its mostly exogenous so acutely from # or iatrogenic disruption to bone or chronic from neglected wounds in diabetes/ulcers
In children it is more likely haematogenous spread from sepsis & due to their immature immune systems
If adult is haematogenous then the vertebra is most commonly affected
