1.2 Bone Growth and Repair Flashcards
Two patterns of bone formation
1) intramembranous ossification
2) endochondral ossification
4 steps of intramembranous ossification
1) development of the ossification center
- –specific chemical messages cause mesenchyme to cluster and differentiate to osteoprogenitor cells then osteoblasts; osteoblasts secrete the organic extracellular matrix of bone
2) calcification
- – secretion stops and the cells (now osteocytes) extend towards canaliculi; in a few days, calcium and other mineral salts are deposited and extracellular matrix hardnes
3) formation of trabeculae
- – extacellular matrix forms and develops into trabeculae, where blood vessels associated with it then differentiates into red bone marrow
4) development of the periosteum
- –mesenchyme condenses at the periphery of the bone and develops into the periosteum
endochondral ossification
replacement of cartilage by bone
most bones are formed this way
chondroblasts
secrete cartilage extraceullar matrix, producing a cartilage model made of hyaline cartilage
note: the perichondrium is the covering around the cartilage model
steps of endochondral ossification
1) development of the cartilage model
- –special chemical signals causes mesenchyme to cluster and form chondroblasts
2) growth of the cartilage model
- –this model grows in length by continual cell division of chondrocytes, and with further secretion of ECM
3) Development of primary ossification center
4) development of medullary (marrow) cavity
5) development of the secondary ossification centers
6) formation of articular cartilage and the epiphyseal (growth) plate
interstitial (endogenous) growth
type of cartilaginous growth
appositional (exogenous) growth
growth of cartilage in thickness due to deposition of ECM on the cartilage surface of the model by new chondroblasts
growth in length of boen involves 2 major events
1) interstitial growth of cartilage on the epiphyseal side of the epiphyseal plate
2) replacement of cartilage on the diaphysial side of the epiphyseal plate with bone by endochonral ossification
four zones of epiphyseal plate
zone resting cartilage
zone of proliferating cartilage
zone of hypertrophic cartilage
zone of calcified cartilage
bone remodeling
ongoing replacement of old into new bone tissue
bone resorption
removal of minerals and collagen fibers from bones by osteoclasts
boen deposition
the addition of minerals and collagen fibers to bone by osteoblasts
factors affect bone growth and remodeling
minerals, vitamins, and hormones
Calcium, phosphorus, magnesium, vitamin A, D, K and B12, and insulin-like growth factors (IGFs)
Stress fracture
microscopic fissures in bone that forms w/o evidence of injury to other tissues
repair phases of bone fracture
- Reactive phace:
- Reparative phase: fibrocartilaginous callus formation
- Reparative phase: Bony calus formation
- Bone remodeling phase
Reactive phace:
early inflammatory phase where blood forms around site (called a fracture hematoma); phagocytes and osteoclasts remove and damaged the dead tissue
Reparative phase: fibrocartilaginous callus formation
cells from periosteum develop into chondroblasts and produce fibrocartilage in this region
Reparative phase: Bony calus formation
near the healthy bone tissue, osteoprogenitor ells become osteoblasts and produce spongy bone trabeculae (join the living and dead portions of the orig bone fragments)
Bone remodeling phase
final phase; dead portions of orig fragment get slowly absorbed by osteoclasts.
compact bone replace spongy around the structure
4 types of fracture
- Open (compound): bone protrude through skin
- Comminuted: into many pieces
- Greenstick: broken on one side but the other bends
- Impacted: forcefully driven into the interior of another
parathyroid hormone
increases blood Ca2+ level
calcitrol
hormone that promotes absorption of Ca2+ from food in the GI tract into the blood
calcitonin
hormone that decreases blood Ca2+ level; inhibits the activityof osteoclasts and increases Ca2+ deposition
