B6-068 Bone Development Flashcards
osteocytes maintain bone matrix/calcium homestasis via […] which regulates serum phosphate
FGF23
what germ layer generates the axial skeleton?
paraxial mesoderm
what germ layer forms the appendicular/limb skeleton?
parietal/somatic layer of the lateral plate mesoderm
what germ layer forms the craniofacial bones?
neural crest cells
mesenchyme differentiates directly into osteoblasts, which form bone
intramembranous ossification
the flat bones of the skull are formed via
intramembranous ossification
frontal, parietal, and upper occipital
what bones are formed via endochondral ossification?
lower occipital
long bones of limbs
vertebrae
ribs
sternum
lengthens due to ossification that occurs at the growth plates
diaphysis
**contains primary ossification center
the primary ossification center develops in the
diaphysis
secondary ossification occurs at […]
two growth plates
the two growth plates of secondary ossification are located where?
between epiphyses and metaphyses
how does vascularization occur in endochondral ossification?
chondrocytes secrete MMPs to degrade ECM
blood vessels invade those new spaces and bring osteoprogenitors
5 zones of the epiphyseal plate
reserve/resting zone
proliferation zone
hypertrophic cartilage zone
zone of calcification of cartilage
zone of ossification
[what zone?]
chondrocytes anchor plate to osseous tissue of epiphysis
reserve/resting zone
[what zone?]
chondrocytes proliferate
proliferation zone
[what zone?]
chondrocytes increase in size; accumulate ALP
hypertrophic cartilage zone
[what zone?]
cartilaginous matrix calcifies, chondrocytes secrete MMPs and apoptose
zone of calcification of cartilage
[what zone?]
chondroclasts on diaphyseal side break down calcified cartilage and osteoblasts and replace with mineralized bone
zone of ossification
most common form of skeletal dysplasia
achondroplasia
achondroplasia is caused by a mutation in […] that affects ability of cartilage to form bone
FGF receptor 3
affects endochondral ossification resulting in short limbs, large skull, small midface, and prominent forehead
achondroplasia
90% of babies with disproportionate dwarfism have
achondroplasia
inhibits the proliferation and hypertrophic differentiation of cartilage cells when activated
FGF receptor 3
a defective FGFR3 gene leads to
constitutive activation of FGFR3
-inhibits chondrocyte proliferation in zone of proliferation
-inhibits chondrocyte differentiation and hypertrophy in zone of hypertrophy
-slows ossification in zone of ossification
conditions of hyperpituitarism [2]
acromegaly
gigantism
caused by a severe maternal deficiency of vitamin D
congenital ricketts
linked to defects in COL1A1 or COL1A2
osteogenesis imperfecta
head bones that protect the brain and sensory organs
neurocranium
head bones that form the face, palatal bones
viscerocranium
the membranous part of the neural cranium forms the [3]
frontal
parietal
upper occipital
narrow seams of connective tissues that temporarily separate flat bones of the skull
sutures
wide sutures where >2 bones meet
fontanelle
the sutures and fontanelles of the skull eventually close via […]
intramembranous ossification
prechordal chondrocranium is derived from
neural crest
chordal chondrocranium is derived from
paraxial mesoderm
the prechordal and chordal cartilages of the neurocranium eventually fuse via […]
endochondral ossification
the viscerocranium is formed via [….] ossification
intramembranous
the viserocranium is derived from
neural crest
[…] cells are vulnerable to ethanol, retinoic acid
neural crest
prematures closure of sutures
craniosynostosis
premature closure of the sagittal suture results in
long, narrow head
prominent fontal and occipital regions
unilateral premature closure of the coronal suture
plagiocephaly
plagiocephaly results in
asymmetric flattening of the skull
bilateral premature closure of the coronal suture
brachycephaly
brachycephaly results in
tall skull with flat frontal and occipital regions
skull shortening in ventral/dorsal axis
**coronal fusion
delayed closure of fontanelles
cleidocranial dysostosis
due to defect in Runx2 gene
cleidocranial dysostosis
enlargement of skull bones
wide set eyes
under-developed clavicles
cleidocranial dysostosis
skull fails to expand
brain fails to grow to normal size causing intellectual disabilities
microcephaly
what happens after re-segmentation during vertebral column formation?
- lower and upper halves of 2 successive sclerotomes form a vertebrae
- myotomes bridge the discs
- arteries pass over vertebral bodies
- spinal nerves lies near IV discs and leave the vertebral column via bilateral foramina
lateral curvature of spine
scoliosis
small defects in vertebral arches but spinal cord is relatively intact
skin covers defect
spina bifida occulta
vertebral arches fail to form
neural tube fails to close
spina bifida meningocele
sternum depressed posteriorly
pectus excavatum
anteriorly projecting sternum
pectus carinatum
mesenchymal progenitors differentiate to form chondroblasts which then form chondrocytes that make a cartilage model for subsequent bone formation
endochondral ossification
bulging frontal and occipital regions with long and narrow head
premature closure of sagittal suture
flat frontal and occipital regions indicates premature closure of
coronal suture
responsible for creating new bone from cartilage models that results in lengthening of diaphysis
epiphysis
widened region of bone on both ends of long bones near the epiphysis
metaphysis
mesenchymal cells differentiate directly into osteoblasts
intramembranous ossification
during endochondral ossification, as the matrix calcifies the chondrocytes are cut off from nutrients and apoptose forming the
medullary cavity
bones increase in diameter via
appositional growth
appositional growth occurs beneath the
periosteum
