Bone Formation Flashcards
intramembranous ossification is typical where
flat bones
name flat bones - 4
part of mandible
maxilla
occipital
temporal and parietal vones
what does metaphysis mean
head, spongy
what is periosteum
dense ct sheath with osteoprogenitor cells
what is diaphysis
middle
what is epiphyseal line
remnant of epiphyseal plate
where does intramembranous ossification take place
within plates of mesenchymal cells
(derived from mesoderm layer)
describe intramembranous ossification - 1
group of mesenchymal cells differentiate (need signal) into osteoblasts (primary ossification center)
synthesis of extracellular matrix
encapsulation of osteocytes
formation of spicules
what is a bone spicule
piece
made by osteoblasts
or
chewed up by osteoclast
describe intramembranous ossification - 2
several similar secondary ossification centers develop on the periphery
the mesenchymal cells differentiate into periosteum
Ossification centers grow radially and fuse
resulting bone is spongy
describe intramembranous ossification - 3
same concept as primary ossification centers
ossification grows out of sites
makes one sheet of bone by fusing together (like soft spot on baby head)
forms periosteum - eventually fuses to flat bone
describe perichondrium vs periosteum
perichondrium = around cartilage
periosteum = around bone BUt has osteoprogenitor cells
both dense ct
where does endochondral ossification take place
within a piece of hyaline cartilage with a similar shape of bone to be formed
all long bones in body come from piece of hyaline cartilage
what is cartilage surrounded by (endochondral ossification)
perichondrium
Except in future articular surfaces
describe primary ossification center of endochondral ossification - 1
at level of diaphysis
perichondrium is transformed into periosteum which deposits bone = bone collar
describe primary ossification center of endochondral ossification - 2
bone collar prevents diffusion of nutrients
cartilage degenerates (hypertrophy and cell death followed by calcification of ECM)
describe primary ossification center of endochondral ossification - 3
blood vessels invade from perichondrium/periosteum
invade spaces left by the degenerating chondrocytes
pushes through bone collar lengthwise through cartilage and drags periosteum with it - and osteoprogenitor cells which create osteoblasts
describe primary ossification center of endochondral ossification - 4
differentiating osteoblasts divide and secrete ecm
ecm made lengthwise - makes space for future bone marrow canal
chewed up cartilage and lots of bone marrow spicles
describe secondary ossification center of endochondral ossification - 1
take places at epiphysis of the future bone (head)