7.6 The Spine Flashcards
(117 cards)
1
Q
What is the function of the axial skeleton?
A
- Weight bearing
- Mobility
- Protecting the spinal cord
- Is adapted for weight transmission in the upright posture
2
Q
What is the axial skeleton?
A
The section of the skeleton that lies along the axis of the body, so the spine, skull (including ear and hyoid bones), clavicle and ribs.
3
Q
How many elements make up the spine?
A
33 vertebrae (although this can vary depending on number of coccygeal bones present)
4
Q
What are the sections of the spine? (In order, top to bottom)
A
Cervical Thoracic Lumbar Sacral Coccygeal
5
Q
How many cervical vertebrae are there?
A
7
6
Q
How many thoracic vertebrae are there?
A
12
7
Q
How many lumbar vertebrae are there?
A
5
8
Q
How many sacral vertebrae are there?
A
5, but they are fused together
9
Q
How many coccygeal vertebrae are there?
A
4 generally, but this can vary as they are vestigial bones - there can sometimes be more
10
Q
How many cervical nerves are there?
A
8, as one emerges from the top of C1, and C8 emerges from between C7 and T1
11
Q
Where does the spinal cord end?
A
L1-L2
12
Q
What does the spinal cord become after L1-L2?
A
The cauda equina (or horse’s tail)
13
Q
What are the two gross structures of a vertebrae?
A
The vertebral body and the vertebral arch
14
Q
Draw out a vertebral body freehand.
A
Do it! Now!!
Can’t add pictures so please actually do it
15
Q
What is the name of the region through which the spinal cord/cauda equina passes?
A
The vertebral foramen or canal
16
Q
What is the spinous process?
A
A projection of bone on the posterior side of the vertebra. Provides site of attachment for various muscles and ligaments.
17
Q
What are the transverse processes?
A
Small bony projections on the left and right sides of the vertebra/vertebral lamina. Provides sites of attachment for muscles and ligaments.
18
Q
What is the lamina?
A
These are flat plates of bone from which processes come off that originate from the pedicles of the vertebral body and form the posterior outer wall of the spinal canal/foramen, protecting the spinal cord.
19
Q
What are the pedicles?
A
Small, cylindrical projections from the vertebral body that connect it to the vertebral lamina, acting as a bridge. Also provide the sides of the spinal canal, protecting the spinal cord
20
Q
What are the inferior and superior articular process?
A
Superior is on the top and extends/faces upwards whereas the inferior is on the bottom of the vertebra and projects/faces downwards. These are on both sides of the vertebrae, and allow for the articulation between adjacent vertebra - superior surfaces correspond with inferior ones on the next vertebra along.
21
Q
What is the function of the vertebral body/centrum?
A
In humans, the body has adapted to transfer body weight during upright walking and standing. Protects the spinal cord on the anterior side, stiffens the body and provides attachment for the pelvic and pectoral girdles as well as many muscles.
22
Q
- What is an easy way to remember the direction in which a lumbar puncture enters?
A
Lumbar Puncture Lamina Pedicle (back to front)
23
Q
What is the general shape of the spine?
A
It has curvature - a gentle S shape
24
Q
What is the function of the curvature of the spine?
A
Allows for flexion and extension
25
What is lordosis?
Posterior CONCAVITY - inward curvature
26
What is kyphosis?
Posterior CONVEXITY - outward curvature
27
What can extreme lordosis result in?
Swayback
28
What can extreme kyphosis result in?
Hunchback
29
What is the normal curvature of the cervical spine?
Gentle lordosis
30
What is the normal curvature of the thoracic spine?
Gentle kyphosis
31
What is the normal curvature of the lumbar spine?
Gentle lordosis
32
What is the normal curvature of the sacral spine?
Slight posterior concavity
33
Which normal curvatures are not present in early life?
Cervical and lumbar lordosis - these develop as the baby begins to sit up (6-8 weeks for sitting, 3 months for confident sitting position). Kyphosis is always present, lordosis develops with time and posture development.
34
What is scoliosis?
The vertebrae no longer align medially/are curved rather than straight (best seen on a sagittal image), most commonly in the thoracic region.
35
From where does the skeleton form during embryo development?
* Craniofacial skeleton forms from the cranial neural crest
* Appendicular/limb skeleton forms from the lateral plate mesoderm
* Axial skeleton forms from the somites (that are formed from the paraxial mesoderm)
36
What affects axial skeleton development from the somites?
* Patterning genes (e.g. transcription factors such as Hox and PAX genes) control somite to axial skeleton differentiation
* Formation of cartilage and bone from intermediate tissues (in all three origins of bone) is controlled by genes that regulate organogenesis, such as transcription factors, cytokines, growth factors and extra cellular matrix molecules.
37
What does the medial sclerotome of somites undergo?
Endochondrial ossification, formation of bone from chondrocytes. This will form the axial skeleton.
38
How are medial somite cells induced to form the sclerotome?
Through the presence of sonic hedgehog (Shh) that is expressed by the notochord - the factor causes differentiation and movement of medial sclerotome/side closest to the notochord.
39
What is the medial sclerotome formed from?
Somite cells from the medial side/closer to the notochord
40
Once differentiated, what do the medial sclerotome cells do?
They migrate around the neural tube and then condense (condensation of chondrocytes) to begin to form the vertebrae.
41
What does the rest of the somite become?
Most lateral cells form the surrounding dermatome and spread out. A few cells between the sclerotome and the dermatome/in the middle become the myotome, becoming migratory cells to form surrounding musculature (e.g. limb and ventrolateral)
42
How are the vertebral discs formed?
A fissure occurs in the mid-somite, which forms the intervertebral disc space.
43
What are the primary and secondary ossification sites for C3-L5 vertebrae?
* Primary: Body/centrum and pedicles/surrounding neural arch.
* Secondary: spinous process, transverse processes and ring/annular epiphyses on the upper and lower surfaces of the vertebral bodies
44
* What are the primary and secondary ossification sites for C1 and C2?
C1
• Primary: anterior arch, one for each posterior arch
• Secondary: none
C2
• Primary: same as C3-L5 (body, two for the arches) with two additional for the odontoid process
• Secondary: tip of the dens, allowing it to fuse
45
What happens to the sclerotomes one they fissure?
The lower half of one fuses with the upper half of the somite below it, and will then undergo chondrification and ossification to form vertebrae. INTERSEGMENTAL VERTEBRAE FORMED.
46
What controls segmental vertebral formation?
Homeotic or HOX genes
47
* What is an example of an experiment showing the effect of HOX genes?
Antennapedia Knock-out in Drosophila - this is where a mutation in the HOX gene antennapedia (that controls leg formation). Failure of this gene to be regulated results in legs being formed where antennae should be in fruit flies, as observed in knockout flies for this gene.
48
What are the HOX genes?
A cluster of homeobox-containing genes. Encode for transcription factors, pattern the principle axis of the animal body.
49
What are homeobox genes?
Genes that pattern the body axis
50
How are HOX genes expressed?
Co-linearly (straight lines on both top and bottom of the embryo).
51
How well conserved are HOX genes?
Highly conserved - same between mice and flies.
52
How are segmental levels determined?
Through overlapping gene expression, resulting in various combinations and concentrations of different factors.
53
* What is an example of a HOX gene deletion resulting in a skeletal abnormality?
HOX D4 knocked out in a mouse, results in transformation of axis vertebra - C2 made into an atlas-like structure (like C1)
54
What are some examples of abnormal spinal development?
* Spina bifida - neural tube defect, failure of spines/arches in one or more vertebrae to develop.
* Hemivertebrae - vertebral defect, may cause scoliosis
* Abnormal curvature - e.g. kyphosis or lordosis
55
What is spina bifida?
This is where the neural tube fails to close, with several degrees of severity:
• Spina bifida occulta - small cyst on spinal cord as not closed at caudal end, can be ripped off during trauma and cause unexpected paralysis. Least aggressive, syndrome often isn’t noticed until scanned. Usually indicated by a hairy region on the skin covering the cyst.
• Meningocoele - this is where a sac protrudes from the spinal column, but only contains spinal fluid, not nervous tissue. Not as severe, incomplete vertebral arch allows some CSF to form a cyst but is contained within the dura and arachnoid mater.
• Meningomyelocoele - this is the most severe form of this disorder, where nervous tissue is found within the protruding sac - neurological emergency as infection in sac is life-threatening. Surgery needs to be completed and baby kept in a sterile environment to give the baby a chance.
(• Anencephaly - this is a disorder where sections of the skull and brain are missing due to a failure of the rostral end of the neural tube to close. Most are born stillborn, the rest die within a few weeks.)
There are very few of these cases seen in England today due to neonatal imaging.
56
How can development affect curvature?
Can massively affect posture - scoliosis, kyphosis (hunchback) and lordosis (swayback) are all possible.
57
What are hemivertebrae?
Vertebrae that are only half formed - this affects alignment of the spine, so when it occurs will present as scoliosis.
58
What are the regional specialisations for the cervical spine?
* Small bodies
* Large vertebral foramina (spinal cord large at this point)
* Foramina transversaria (where the blood vessels supplying the head and neck travel through)
* Bifid spinous processes
* Articulation facets on the anterior/posterior sides to allow for flexion and extension but not rotation
* Vertebra prominens in C7
59
Which cervical vertebra does NOT have transverse foramina/foramina transversaria?
C7
60
What is the vertebra prominens and a useful feature of it?
Particularly large spinous process on C7, easily able to be palpated (lies just at the level of the collarbone) so is a good reference point to then palpate other vertebrae.
Difficult to see because of the shoulders, so cervical spine cannot be cleared unless T1 can be seen (multiple views may be necessary).
61
Which cervical vertebrae are considered atypical?
The first two - C1 (atlas) and C2 (axis) - and the last, C7.
62
What is atypical about the atlas/C1?
* Lacks a body/centrum and a spinous process
* Anterior and posterior arches with lateral masses/tubercles
* Superior lateral masses are articulation points for the occiput/occipital chondyles at the atlo-occipital joint
* Inferior articular surfaces articulate with the axis at the atlo-axial joint.
* Groove for vertebral artery
* Contains a facet for the dens of the axis
63
What is atypical about the axis/C2?
It has an odontoid process (aka the dens) projecting from its superior surface, otherwise typical (with bifid spine). The dens projects into C1 and allows for the axis to rotate.
64
* From where is the dens derived?
From C1
65
What is the function of the dens?
To allow C1 to rotate
66
* Does the dens need to be viewed in an upper cervical x-ray?
Yes, the x-ray can only be cleared if the dens is shown to be undamaged/there is a clear view.
67
What ligaments hold the atlas and axis in place?
* Transverse ligament (posterior to dens, runs across C2)
* Alar ligament (anterior to dens, connects dens and occipital condyles)
* Superior band of cruciate ligament (superior to dens, runs along anterior-posterior plane)
* Apical ligament (superior to dens, attaches upwards)
68
* What could happen during rheumatoid arthritis of the atlo-axial joint?
Transverse ligament wears down, resulting in atlo-axial subluxation (incomplete/partial dislocation). This can cause paralysis if hear is tilted too far back due to full dislocation then occurring.
69
What are the regional specialisation of the thoracic vertebrae?
* Smaller vertebral foramen (spinal cord smaller here/especially in comparison to vertebra size)
* Long spines
* Costal facets for rib articulation
* Articulation facets for adjacent vertebrae lie antero-posterior, allowing for some rotation but almost no flexion or extension - cumulatively allow for a good degree of rotation.
70
Which ribs are atypical?
Ribs 1, 11 and 12 only articulate with 1 vertebrae rather than the normal 2
71
How many vertebrae do ribs normally articulate with?
2
72
What are the regional specialisation for lumbar vertebrae?
* Large bodies
* Interlocking intervertebral articular facets that allow flexion and extension but prevent rotation
* Built for strength and support - requires a huge amount of force to fracture one, so damage to the lumbar spine suggests that the rest of the spine should also be checked for fractures.
73
What is the function of intervertebral discs?
To act as spacers between vertebrae (CANNOT be a shock absorber or else it would produce too much heat)
Facilitate weight transmission and stability of spine
74
What happens to vertebral discs with age?
Get smaller with age, and the sac surrounding the nucleus pulposus becomes weaker, increasing risk of hernia toon and impingement of nerve roots.
Sciatica is less common in young patients as their discs should be well hydrated, limiting decreases in space and chances of herniation.
75
What are the regional specialisation of the sacral vertebrae?
* Fused (still with foramina to allow for nerve root exits)
| * Large surface for articulation with the pelvis
76
What are the specialisations of the coccygeal vertebrae?
* Lower 3 fused
| * Vestigial (no real function) and can be of variable number
77
What type of joint are the sacral and coccygeal joints?
True synovial
78
* How do hormones affect pelvic ligaments?
During late stages of pregnancy/childbirth, oestrogen and progesterone cause the pelvic ligaments to relax, allowing for the opening of the birth canal.
79
What are the three types of joints?
* Fibrous
* Cartilaginous
* Synovial
80
What type of joint is the atlanto-occipital joint and what function does it have?
* Synovial joints between occipital condyles and atlas
| * Allows for flexion, extension and lateral flexion
81
What type of joint is the atlanto-axial joint and what function does it have?
* Synovial joints between odontoid process and lateral masses of the axis and of the atlas.
* Allows for extensive rotation
82
What type of joints are the joints between vertebrae below C2?
* Synovial joints between articular processes
| * Cartilaginous joints between vertebral bodies
83
What are intervertebral discs?
Cartilaginous joints between vertebral bodies - secondary cartilaginous.
84
What is the structure of an intervertebral disc?
* Peripheral annulus fibrosis - fibrocartilage, surrounds and protects
* Central nucleus pulposus - gelatinous with high water content.
The disc becomes less fluid and more fibrous with age. A well-hydrated space should be retained.
85
What happens during a disc herniation?
The nucleus pulposus bursts out of the surrounding annulus fibrosus, impinging on nerves and often causing pain.
86
What are the ligaments supporting the spine?
Longitudinal:
• Anterior
• Posterior
Between adjacent vertebrae:
• Supraspinous (joins backs of spinous processes together)
• Interspinous (between spinous processes)
• Intertransverse (joins tips of transverse processes)
• Ligamentum Flavum (joins vertebrae/laminas together, typically very yellow in colour)
Specialised atlantoaxial:
• Apical, alar, cruciate etc
87
What are the longitudinal ligaments of the spine?
Anterior and posterior
88
What are the ligaments between adjacent vertebrae?
Supraspinous, interspinous, intertransverse and ligamentum flavum
89
What are the muscles that move the spine?
Flexors:
• Anterior and lateral
Extensors:
• Back (e.g. erector spinae - very important for keeping us upright)
• Long and short
Flexion, extension and lateral flexion:
• Cervical and lumbar extensive
• Restricted thoracic (rotation is limited in the thorax)
90
What are the flexor muscles for the spine?
Anterior and lateral muscles
91
What are the extensors of the spine?
Muscles on the back (e.g. erector spinae), and the long and short muscles.
92
What are the muscles that allow flexion, extension and lateral flexion of the spine?
Cervical and lumbar extensive muscles. Restriction seen in the thorax.
93
In which part of the spine do muscles restrict rotation?
Thoracic
94
What is the major function of erector spinae?
Maintains posture
95
What are the specific muscles for head movements?
Head and neck flexors, as well as lateral flexors - the scalene muscles
96
What region of the cervical spine is especially important and why?
C5-7, need to see if these are still intact as these nerve roots allow for independent breathing (phrenic)
97
Where does the spinal cord occupy?
The vertebral canal
98
Where does the spinal cord terminate in adults?
Lower border of L1
99
Where does the spinal cord terminate in children?
Lower border of L3
100
Where are there enlargements in the spinal cord?
Cervical and lumbar spine have enlargements
101
What happens to the spinal cord at L1 in adults/L3 in children?
Cord tapers to an end caller the conus medullaris, nerve roots continue from here as the cauda equina
102
From where do nerve roots typically emerge?
From below the vertebra for which they are named (nerve C1 is atypical and emerges from the top of the vertebra)
103
How many pairs of nerve roots are there?
31 (remember, 8 in cervical spine)
104
What fibres make up the nerve roots?
Mixed, so contain motor, sensory and autonomic nerves
105
What happens to the nerve roots lower down in the spine?
They increase in course and obliquity (tilt)
106
Where does the subarachnoid space end?
At S2
107
Draw cross section of nerve roots/spinal cord
Do it!!!
108
What do spinal cord injections need to pass through?
The dura
109
How do spinal nerves leave the vertebral canal?
Via the intervertebral foramina
110
What are the most commonly affected areas for a prolapsed disc?
Lower cervical and lower lumbar regions (lumbar most common)
111
Which direction of prolapse is most common?
Postero-lateral Prolapse most common (outwards and backwards)
112
What is compressed during a disc prolapse?
The nerve roots and spinal cord - in lower lumbar vertebrae, the cauda equina can become impinged
113
What are the preparatory steps for a lumbar puncture?
History, examination, fundoscopy (check for raised cranial pressure), positioning of patient (curled up, arching back to maximise space between vertebrae)
114
Where are lumber punctures inserted?
Between the L4/L5 interspace between vertebrae
115
What is the procedure for a lumbar puncture?
Layers accorded for en route - skin is thicker than the sub-arachnoid space (1-4 inches thicker)
116
What is the purpose of a lumbar puncture?
To check if there are organisms/infections, malignant cells or increased protein levels present within the CSF - diagnostic.
117
Why do lumbar punctures occur at L4/L5?
As cerebrospinal fluid (CSF) can be sampled from the lumbar cistern where no damage to the spinal cord will occur (‘hairs’ in the ‘horse’s tail’ will just be pushed aside by the needle).
