module 9 bone formation Flashcards
axial skeleton
80 bones
skull
vertebral column
thorax
appendicular skeleton
126 bones
upper and lower extremities
shoulder girdle
pelvic girdle
bone cells
osteoblast
osteocyst
osteoclast
osteoblast
derived form mesenchymal cells produce type 1 collagen responde to parathyroid hormone produce osteocalcin synthesize osteoid (nonminderalized bone matrix)
osteocyte
transformed osteoblast surrounded in osteoid as it hardens from deposited minerals
- maintain bone
- help regulate Ca and Phos.
- stimulated by calcitonin
- inhibited by PTH
osteoclast
from hematopoetic tissue (monocyte/macrophage lineage)
major reabsorptive cell of the bone
large, multinucleated cells
contain lysosomes filled with hydrolytic enzymes
bone maxtrix
organic part: 25% - collagen - proteoglycans - glycoprotines inorganic part: 65% - calcium - phosphate -- crystals of these minerals called hydroxyapatite
osteoid
organic matrix
- collagen fibers extend along parallel lines of tension: give bone tinsel strength and some flexibility.
proteoglycan
part of osteoid
polysaccaride that binds between collagen fibers and surrounds cells.
may transfer mechanical info within matrix
Inorganic matrix
mineral content bound and embedded in in matrix gives bone hard, rigid structural strength reservoir for the body calcium and phosphorus
basic unit of bone
osteon or the harersian system
haversian canal
blood vessels and nerve fibers run through this
-surrounded by mineralized matrix: lamellae
lucunae
small cavities bordering the lamellae that contain a bone cell, osteocyte.
canaliculi
small channels that connect adjacent lamellae, allows nutrients to move through
2 bone types
cancellous/trabecular/spongy
compact/cortical
cancellous/spongy bone
network of thin plates and rods: trabeculae
- found within ends of long bones, vertebral bodies, flat bones (pelvis)
- trabeculae laid in response to stress and shaped to accommodate loads placed on bone
- enclosed in shell of compact bone
compact/cortical bone
resistant to compression
dense in structure
laid in concentric layers
periosteum
tough fibrous memrane that covers all bone
- highly vascularized
- provides nutrition via volkmann canals
- inner layer contains osteoblasts
- covers entire bone except for the ends which are covered by hyaline (articular) cartilage
long bones
medullary cavity: central cavity is present
- endosteum: thin membrane that lines inside of cavitiy
- – contains osteogenic cells
- in children: filled with red marrow
- in adults: largely yellow marrow
- – red marrow primarily in flat bones of adults
endochondral ossification
longitudinal bone growth, evident in embryonic development, fracture healing, some bone tumor growth.
- mesenchymal cells differentiate into chondrocytes which produce a carilaginous “model” of bone
- mineralized starting at center (primary assification)
endochondral secondary ossification
centers form near ends of long bones ( epiphyses)
- future site of bone growth into teen years.
intramembranous ossification
flat bones grow by circumferential growth process
- vascularized fibrous tissue becomes mineralized as the mesenchymal cells present differentiate into osteoblasts.
continuous bone growth
bones increase in length only through growth within cartilage plate followed by endochondral ossification
epiphyseal plate
allows for lengthening of diaphysis and metaphysis
- site of continuous growth
growth and thickening of cartilage cells of the plate move the epiphysis away from the metaphysis
- calcification and replacement of cartilage occur on metaphyseal surface
