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13 Cards in this Set

  • Front
  • Back
-Woven bone (immature), spongy/cancellous bone vs. Lamellar (mature), compact bone
Ossification Methods
Intramembranous Ossification
-CT directly change into bone
-fibrous tissue to bone
-in face and cranium, not alot of cover b/c want it to be light
Endochondral Ossification
-a cartilage model is first formed
-bone extremities, vertebral column, pelvis and bones of base of skull
Endochondral Ossification
Primary Centers of Ossification
-Changes occurring at perichondrium:
formation fo periosteal band by intramembranous ossification
perichondrium changes to periosteum (can still produce chondroblasts)
Periosteal band keeps growing and forms compact bone of shaft
-Changes occurring in middle of the cartilaginous model:
Chondrocytes hypertrophy and matrix thins
matrix mineralized by chondrocytes
chondrocyte degenerate and die
-Periosteal bud invaision:
periosteal bud (capillaries and osteogenic cells) inbades hypertrophied cartilage
establish primary center of ossification
newly formed bone trabeculae contain cores of calcified cartilage

Secondary Centers:
develop in epiphyses
cartilage canals invade from perichondrium (not articular or physis)
canals contain venules and arterioles that end in capillary glomerulus
chondrocytes close to capillary undergo hypertrophy and degeneration
calcification of the cartilage
multiple foci of calcification develop around each glomerulus
all foci fuse to form secondary center of ossification
Growth of Bone in Length form Physis
-growth in length is result of endochondral ossification occurring at physis region
-increase in diameter due to intramembranous ossification
-easy to break here and growth stopped by Gonadotropic hormones
Zones of Physis Region
-Resting (reserve) zone
hyaline cartilage with randomly distributed chondrocytes, normal cartilage

-zones of proliferation
larger chondrocytes forming columns at right angle to epiphysis, dividing rapidly
-zone of hypertrophy
cell increasing in size, Ca accumulation in matrix, wall bte last 2-3 chondrocytes is calcified
-zone of resorption
capillary loops and perivascular connective tissue invade lacunae
-zone of ossification
trabeculae of bone deposited on remains of calcified cartilage
Groeth of Bone in Width and Circumference
-concurrent periosteal growth and endosteal resorption leads to increase in size of medullary cavity
-slower endosteal resorption than pwriosteal deposition leads to thickening of shaft wall
in growing bone
-ridges and grooves on the surface
-osteoblasts deposit osteoid around blood vessels in grooves. grooves form tubes by closure of growing edges
-more concentric layers of sdteocytes are added forming primary osteons which are replaced by secondary osteons
in mature bone
-slow appositional growth in subperiosteal and endosteal region adds outer and inner circumgerential lamellae
Bone Modeling
-bone changes shape and size
-occurs due to concurrent resorption and deposition
Bone Remodeling
-bone constantly replaced
-does not alter the shape and size of bone
-initiates and proceeds only in one direction
-osteoclastic resorption followed by osteogenic formation

Cortical remodeling unit
-leading cutting edge cone(osteoclasts)
-reversal zone(switch from resorption to formation)
-closing zone(osteoblasts add newer lamellae centripetally inwards from cement line)

Spongy bone remodeling
-osteoclasts work on endosteal surface of trabeculae
-osteoblasts add bone on same or opposite surface
Fracture Repair
-mid-shaft fracture leads to formation of blood clot, necrosis of soft tissue and death of osteocytes on each side
Healing by callus formation:
-proliferation of periosteal cells results in lifting of fibrous layer
-thickening of endosteum due to proliferation
-formation of internal callus btw opposing surfaces of bone and external callus surrounding outermost surface of broken bone
-external is formed only when broken ends move
-osteogenic cells close to bone form bone directly
-in areas away from brake, osteogenic cells form cartilage first
Synarthroses (no cavity in middle)
-sligthly movable to highly immovable
-held by dense collagenous/elastic tissue (skull structures)
-connected by cartilage (sternebrae)
-syndesmoses/synchondroses replaced by bone
-hyaline caps on bone edges joined by fibrous bands and fibrocartilage (pubic symphysis, vertebral disks)
joints cont'd
synovial joints (cavity in middle)
-joint capsule formed by outer fibrous layer and inner synovial fluid
-joint cavity filled
-articular cartilage (covers bone ends)
--superificial zone: flat chondrocytes, lacks perichondrium
--middle zone: spherical chondrocytes
--deep zone: chondrocytes arranged perpendicular to articular surface, collagen fibers form btw columns of chondrocytes anchored into calcifid cartilage, calcified cartilage joined to subchondral bone and contains tide marks btw calcified and non-calcified cartilage