Lecture 1- development of vertebral column Flashcards
how many vertebrae in the adult?
33
how many presacral?
24
how many sacral/ coccygeal?
9
How many cervical, thoracic and lumbar?
7, 12,5
how many sacral and coccygeal?
5, 4
Curved segments act like what?
independent springs conferring flexibility and resilience to the structure as a whole
what vertebrae are primary curvatures?
Thoracic, sacral/ coccygeal
what vertebrae are secondary curvatures?
cervical and lumbar
are primary curvatures convex anteriorly or concave anteriorly?
concave
are secondary curvatures convex anteriorly or concave anteriorly?
convex
in a fetus what shape is the vertebral column?
‘C’
when are the thoracic and sacrococcygeal primary curvatures established?
in fetal development
when are the cervical and lumbar secondary curvatures developed?
during infancy
when specifically is the secondary curvature developed in the cervical region?
2-3 months
when specifically is the secondary curvature developed in the lumbar region?
6-8 months
primary curves are maintained through what?
through shape of vertebrae
secondary curvatures arise from what?
from a modification in shape of the intervertebral disc
degeneration of the discs in the elderly results in what?
a return to a more pronounced primary curvature
what is kyphosis?
hunchback deformity
what is lordosis?
sway back deformity, forward pelvic tilt
what can lordosis occur from?
pregnancy
what is scoliosis?
lateral deviation of greater than 10' often accompanied by a rational defect congenital idiopathic secondary to primary condition
adult vertebral body is derived from what?
the juvenile centrum plus a small portion of the neural arch
the adult vertebral body equates to more than what?
the juvenile centrum
ossification is initiated where?
dorsal to the notochord
what kind of ossification is the centra?
true endochondral
when does the centra first appear?
in lower thoracic and upper lumbar regions (T10- L1) between 9-10 fetal weeks
what kind of progression is the ossification of the centra?
- bidirectional progression
when does ossification of the centra reach L5 and C2?
L5 by 3rd month and C2 by end of 4th fetal month
Notochord cells contain what?
angiogenic inhibiting factor which delays vascular penetration into this region
vertebral centra from first trimester display what?
an axial avascular area around the notochord region
what does the axial avascular area around the notochord region result in?
a ring- shaped area of ossification
morphology and development of juvenile centrum is heavily influenced by what?
profuse vascular supply
each centre is supplied by what?
paired nutrient arteries and an accompanying venous network
Where do the neural arches commence?
on the inner surface of the hemi-arch
what comes first?
intramembranous followed by endochondral
where do the neural arches first appear?
in the lower cervical and upper thoracic regions in 2nd fetal month
the neural arches spread where?
spread upwards and downwards
Ossification of the neural arches initiated by what?
in response to gasp reflex- muscle contraction
by the 3rd fetal month what happens in relation to the neural arches?
a second group of centres appear in the lower thoracic and upper lumbar regions
in relation to the 3rd fetal month of the neural arches where do they spread?
upwards and downwards
ossification of the neural arches in the 3rd fetal month is initiated by what?
in response to lower limb movement- muscles contraction
during the first year the neural arches commence fusion where?
posteriorly at the spinous process
Where does fusion of the neural arches occur initially and where does it progress?
in the lower thoracic and upper lumbar regions in the latter part of the first year and progresses in a systematic cranial and caudal direction
cervical arches may not fuse till when?
beginning of 2nd year
lower lumbar arches may not fuse until when?
the end of the 5th year
in an individual <6years what could occur in relation to the neural arches?
non-fusion of the arches should be expected
fusion between the neural arches and the centra occurs where?
ventral to the pedicles at the neurocentral junction
when does ossification of the neural arches and centra occur?
between 2-5 years
adult vertebral bodies formed from what?
centrum and ‘boutons’ of pedicles
head of costal process only ever articulates with what?
boutons and never with the centrum
where does neurocentral fusion occur?
first in lumbar region, followed by cervical segment, with thoracic vertebrae being last to fuse
where does atlas C1 ossify from?
three primary centres
At birth what represents atlas C1?
- two bony masses
- display larger concave articular facets anteriorly on upper surface
- display smaller flatter articular facets on their lower surface
morphology atlas C1 remains what?
unchanged throughout the first year after birth
what happens to atlas C1 in the first or second year?
- ossification commences in the anterior arch
- either as single, paired, multifocal nodules or from ossification bars that extend directly from lateral masses
posterior arch of atlas C1 usually fuses when
4-5 years
what percentage of adults still have an unfused atlas?
1%
anterior neurocentral junction closes when?
5-6 years
line of union between anterior arch and lateral masses passes where?
across the anterior portions of the superior articular facet
endochondral growth occurs where?
at all junctions prior to fusion allowing an overall integrates expansion of the vertebral canal as the 3 ossified units grow away from one another
adults size atlas is reached when?
by 4-6 years
early limitation on size of vertebral canal is a clear indication of what?
- precocious maturation of the CNS
The axis C2 ossifies from what?
5 primary centres of ossification
- one for each half of the neural arch
- one for the true centrum of the axis
- one for each half of the body of the dense
centres for the neural arches in the axis C2 appear when?
before the centra ~ 7-8 fetal weeks
The true centrum of the axis commences ossification when?
from a single centre between 4-5 months intra-uterine life, around the same time two laterally places ossification centres appear in the odontoid process
these laterally placed ossification centres do what?
they rapidly coalesce so that the intradental synchondrosis fuses by birth and forms forked appearance of juvenile dens
In relation to the axis C2 when does the posterior synchondrosis between neural arches fuse?
between 3-4 years
in the axis C2 the dens fuses where and when?
laterally to the neural arches at the dentoneural synchondrosis ~3-4 years
the fusion line of the axis C2 passes where?
across superior articular facet, so that medial 1/3 of facet is formed by dens and lateral 2/3 by the neural arch
In relation to the axis C2 the inferior articular facet forms from what?
entirely from neural arch
in relation to the axis C2 the fusion halts increase what?
in dimension of the vertebral canal
in relation to the axis C2, complete of what occurs between 3 and 4 years?
fusion of the foramen transversarium is complete when?
in relation to the axis C2, what fuses between weeks 4-6?
the dentocentral junction and the paired neurocentral junctions
all lines of fusion of the axis disappear when?
9-10 years
what line of fusion may still be present in relation to the axis C2?
small horizontal cervice may remain in region of posterior dentocentral junction
In relation to the axis what occurs at 2 years?
a small ossific nodule, the ossiculum terminales, appears in the cartliage plug that fills the apical cleft
Os terminale fuses when?
with dens at ~12 years
in relation to the axis C2, what are the 5 secondary centres?
- 2 flake-like epiphyses for the bifid transverse processes
- 2 plate- like epiphyses for the bifid spinous process
- inferior annular ring (only inferior in C2)
when would the 5 secondary centres of the axis C2 become 6?
- is os terminale is considered to be epiphyseal
recognisable secondary centre of ossification occurs with relation to what?
to the inferior annular ring
what infills the interdental groove?
a small tongue of bone progresses up the posterior surface of the dens
how do the typical cervical vertebrae develop?
in accordance with the general ossification pattern of any typical vertebra
what is a typical cervical vertebrae formed from?
3 centres
when is a typical cervical vertebrae recognisable from?
mid- fetal life
all cervical laminae unite where and when?
posteriorly within the 2nd year
when is neurocentral fusion complete within the cervical vertebrae?
3-4 years
once neurocentral fusion takes place in the cervical vertebrae what happens?
synovial uncovertebral joints of luschka form on the sloping and elevated articular sides of the neural element of the vertebral body
in relation to the cervical vertebrae when does single bony element close?
by 4 years
what is luschka?
one cervical vertebrae can articulate with the other
what are the 6 secondary centres in cervical vertebrae?
- 2x transverse processes
- 2x spinous process
- 1x superior annular ring
- 1x inferior annular ring
when do the secondary centres in cervical vertebrae appear?
beginning of puberty
when do the secondary centres in cervical vertebrae begin fusing?
end of puberty (18y+)
when do the secondary centres in cervical vertebrae completely fuse?
by 24 years old
thoracic vertebrae develop in accordance with what?
with general ossification pattern for a typical vertebrae
in relation to the thoracic vertebrae when do the primary centres appear?
present by end of third intra- uterine month
how are the thoracic vertebrae identifiable?
by the 4th intra- uterine month
lumbar vertebrae develop in accordance with what?
general ossification pattern for a typical vertebrae
in relation to the lumbar vertebrae when do the primary centres appear?
present by end of third- intra-uterine month
how are the lumbar vertebrae identifiable?
by the 4th intra-uterine month
What is present in the thoracic and lumbar secondary ossification?
annular ring transverse process spinous process thoracic: sometimes on costal surface lumbar: sometimes on mamillary processes
how many centres does the sacrum have?
21 separate centres
each sacral vertebrae is represented by what?
typical 3 primary centres
what are the primary centres of the sacrum?
1x centrum
2x neural arches
S1 -3 incorporate what, which form what?
paired lateral elements, form the ventral aspect of the alae and are site of SI artic
what is the sacrum ossification pattern?
3rd iu month= S1 and S2 centra
4th iu month= S3 and S4 centra, S1-S3 neural arches
5th iu month= S5 centra, S4-S5 neural arches
6th iu month= S1-S3 paired costal elements
Birth = all centres represented although may only be small ossific nodule
in relation to sacral fusion when do the neural arches unite?
with lateral elements between 2-5 yrs
What do the lateral elements of sacral fusion then fuse with?
the centrum between 2-6 yrs
when do all the primary centres of the sacral vertebrae fuse?
6yrs except post. at spinous processes
when do the posterior spinous processes fuse?
7-15 yrs
individual sacral vertebrae remain separate until when?
puberty when late elements commence fusion
are secondary centres in relation to the sacral vertebrae consistent?
no, numbers vary between individuals
how many secondary constant centres are there in the sacral vertebrae?
14
- 10x annular rings
- 2x auricular epiphyses
- 2x lateral margin epiphyses
what are the multiple small variable elements in relation to secondary centres of the sacral vertebrae?
flake- like epiphyses
- spinous process
- median sacral crest
- lateral sacral crest
- between sacral vertebrae
what happens around 12 years old to the fusion of the secondary centres of the sacral vertebrae?
- lateral elements are fusing the annular epiphyses commence fusion in a caudocranial direction
in relation to the sacral vertebrae spaces an be identified between bodies what age?
<20 years
if space only between S1 and S2 what age?
<27 years
complete union not observed until when?
25+ years
epiphysis for SI joint?
several ossific nodules which coalesce
appears 15-16 yrs, fuse by 18 yrs
lateral margin epiphysis follows same pattern
fusion in the sacral vertebrae goes from where to where?
caudal to cranial
ossification occurs from where to where in relation to sacral vertebrae?
cranial to caudal
sacro-iliac joint forms when?
2nd iu month
sacro-iliac joint completed when?
7th iu month
the sacro-iliac joint at birth it is said to be what?
straight and parallel to vertebral column reflecting quadripedal form
what assists with growth of the sacro-iliac joint?
mechanical forces associated with growth
what causes the sacro-iliac joint to curve?
bipedalism cause the joint to curve caudodorsally into adult morphology
surface area of sacro-iliac joint increases when?
substantially throughout development in line with important developmental milestones
sacro-iliac joint is what?
non- weight bearing and demonstrates no secual dimporphism
each coccygeal vertebrae forms from what?
a single separate centre
Co1 forms from what?
multiple
Co1 appears when?
between late fetal period and first year of life
Co2 appears when?
3-6 yrs
Co3 appears when?
10 yrs
Co4 appears when?
puberty
when are the coocygeal vertebrae recognisable?
puberty
