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Bone CONNECTIVE TISSUE MESODERM (DEVELOPMENT (Intramembranous ossification…
Bone
CONNECTIVE TISSUE
MESODERM
TYPES
Primary
many osteocytes
:arrow_down: mineralization
disorganized/dusty ecm
Secondary
:arrow_up: mineralization
directionality to collagen
fewer osteocytes, have pushed each other far apart
Compact/Dense/Cortical/Lamellar
hard outer part
Haversian systems/osteons
microarchitectural organization
longitudinal canal
osteocyte concentric circles
Spongy/Cancellous/trabecular
webby, lattice-like inside
DEVELOPMENT
Intramembranous ossification
MESENCHYME
differentiation process
ECM stuff dumped on into mesenchyme
leads to
endochondral ossification
bone collar around
DIAPHYSIS
found in
flat bones of cranium
clavicles
patella
small bones of hands/feet
Endochondral ossification
cartilage model
hyaline cartilage replaced
cart dies
vessels perforate
osteoblasts migrate in
bones below the skull
Primary ossification centers
fetal development
Secondary ossification centers
EPIPHYSEAL PLATE
long bone growth
cartilage :heavy_division_sign: pushes epi and dia apart
replaced by bone
only keep thin plate
Histologic zones
resting
proliferation
chondrocytes
:!!: lines
hypertrophy
bigger & swollen
degeneration
mineralized matrix
ossification
osteoblast move in
ORGANIZATION
reading a bone
diaphysis
metaphasis
epiphysis
CELLS
cool info
ecm =
OSTEOID
HYDROXYAPATITE CRYSTALS
Ca2+
+
P crystals
macromolecules
glycoproteins
osteocalcin
sialoprotein
Type I Collagen
origin
mesoderm/Mesenchyme
Neural crest cells: cranial bones
Formation
osteoblasts
immature
osteocyte
mature
lacunae
cell processes :arrow_forward: attached to other cells
Degradation
osteoclasts
from mono/macrophages
multi-nucleate
ruffled border
digest and resorb bone
release Ca2+