Ch 6.5 Bone development Flashcards
describe an early fetal skeleton
cartilage only with perichondrium covering everything except articular surface
what is intramembranous ossificiation?
ossificiation that begins as a membrane, not as cartilage
describe the ossification of skull bones
starts as DFCT that contains osteochondral progenitor cells
periosteum forms around outside, this contains osteoblasts
osteoblasts lay down woven bone
woven bone is resculpted into trabeculae and compact bone to form a dipole bone (compact-spongy-compact)
what is endochondral ossification?
ossification that occurs within cartilage
describe the 8 stages of endochondral ossification
1-begins as hyaline cartilage model with perichondrium
perichondrium has osteochondral progenitor cells undreneath
2-some perichondrium becomes periosteum and forms a “bone collar” around the cartilage
-cartilage model increases in L and W
3-calfied cartilage forms
4-primary ossification center forms
5-vessels enter calcified matrix, bringing osteoblasts and osteoclasts
6-more perichondrium becomes periosteum, cartilage model grows and is made into calficied bone
-osteoclasts carve marrow cavity
7-secondary ossification centers form
8-all cartilage except articular and epiphyseal plate has been converted to bone
what is the model for endochondral ossification?
hyaline cartilage model
what forms the bone collar in the endochondral ossification?
periosteum that forms from the perichondrium
does the cartilage model grow during endochondral ossification?
yes
how does cartilage become ossified during endochondral ossification?
chondrocytes hypertrophy
matrix becomes mineralized
cells die, leaving spaces in the mineralized matrix
describe the formation of the primary ossification center during endochondral ossification
blood vessels enter the calcified matrix, bringing osteoblasts and osteoclasts
osteoblasts produce trabecular bone, making cancellous bone in the center of the bone
while the osteoclasts carve a marrow cavity, what else is happening during endochondral ossification?
more perichondrium becomes periosteum, cartilage model grows, more is calcified and made into trabecular bone
how is the marrow cavity made during endochondral ossification?
osteoclasts carve it in the center of the trabecular bone
where do secondary ossification centers appear?
in both epiphyses
how does the secondary ossification center’s development differ from that of the primary ossification center?
no marrow cavity is carved out
approximately how long, after full term birth, do the secondary ossification centers form?
1 month
