Bone II Flashcards
what does the endosteum line? what does it contain?
marrow cavity
volkmann’s canal
haversian canal
contains osteogenic cells
what are the two was bone develops?
intramembranous bone formation
endochondrial bone formation
what is intramembraneous bone formation?
development within layer of condensed mesechyme
what is endochondrial bone formation?
occurs via a cartilage model that is replaced by bone
what kind of bone is always formed first? followed by what?
primary
secondary - slower remodeling
how does intramembraneous bone formation begin?
when mesechymal cells condense to form a primary ossification center — osteoblasts differentiate and begin secreting osteoid
what happens when osteoblasts become trapped in their own matrix (osteoid)?
they become osteocytes
what is the name given to bone that is formed in the priamry ossification center of IBF?
bone trabecular (fused spicules)
as the trabeculae join together what forms?
spongy bone
what happens at the same time blood vessels invade the area?
undifferentiaed mesechymal cells give rise to bone marrow cells
what fuses together to form bone?
ossification centers
what kinds of bone are formed by intramembraneous bone formation?
flat bones of the skill
what are the five hstiologically distinctive zones starting from the epiphyseal side of the plate?
zone of reserve cartilage zone of cell proliferation zone of cell maturation and hypertrophy zone of calcifying cartilage zone of provisional ossification
what is the zone of reserve cartilage?
cartilage with small randomly arranged inactive chondrocytes
what is zone of proliferation>
rapid mitotic division give rise to rows of cartilage cells
what is the zone of cell matruation and hypertrophy?
chrondrocytes are greatly enlarged and contain glycogen and the cartilage maxtric between neighboring cells becomes thin
what is the zone of calcifying cartilage?
lacunae confluent and the remnants of interlacunar matrices become calcified, causing chondrocytic death
what is the zone of provisional ossification?
bone is beginning to be elaborated upon the calcified cartilage, and osteolytic activaty begins to resorb the calcified bone calfiedi cartilage complex
what two things do not undergo ossification and why?
periosteium and endosteum
develop from portions of the mesechymal layer that do not under ossification
how are long bones formed?
endochondrial bone formation
how does endochondrial bone formation begin?
a segment of hyaline cartilage serves as a model for bone
what are the two stages of endochondrial bone formation?
development of
primary ossification center
seconadary ossification center
where does the primary ossification center develop?
midriff of the diaphysis
what is teh periosteum?
vascularization of the perichondrium = osteoprogenitor cells –> osteoblasts
how is the subperiosteal bone collar formed?
osteoblasts secrete matrix deep to perichondrium via intramembraneous bone formation
what happens to the chondrocytes qwithin the core of the cartilaginous model?
undergo hypertrophy and degen. = forming marrow space
what is in the periosteal bud?
blood vessels
osteoprogenitor cells
mesenchymal cells
where do secondary ossification centers develop?
epihysis
what occupys howships lacunae?
osteoclasts - multinucleated
what are monocyte precursors?
osteoclasts
the inner layer of teh periosteum possesses what?
osteoprogenitor cells
what is teh outer periosteum?
fibrous
what is the function of the periosteum?
to distribute blood vessels to bone - apposition growth!
how do osteocytes communicate with eachother?
through gap junctions on proceses that extend through canaliculi
what will a diet deificny in calcium lad to?
fragile bones
what does excessive growth hormone cause?
acromegaly
what does excessive vitamin D cause?
bone resorption
what will an excess or deficinecy in vit A leads to (extremes)?
short stature - epiphyseal plates closing early
what does hypervitaminosis A do?
accelerate ossification of epithyseal plates
what does hypovitaminosis A do?
reduce the width of the epiphyseal plates
what happens in the absence of vitamin D?
epiphyseal chondrocytes continue to proliferate but matrix does not calcify – increase osteoid - unmineralized = rickets
what are the primary manufacturerrs of collagen in long bones?
osteoblasts
