Bone Flashcards
Types of bone
flat, short, long, sesamoid, irregular, sutural
Functions of bone
weight bearing, protection, blood formation, mineral store
osteons
compact bone organised in circular structures
Haversian canals
runs inside osteons
osteocytes and concentric rings of bone matrix
wrap around Haversian canals and are the inside of osteons
other names for spongy bone
trabecular
what is in spongy bone
network of lamellated trabeculae filled with bone marrow. no Haversian canals
orientation of trabeculae reflects
main direction of mechanical forces
cells in bone
osteocytes, osteoblasts, osteoclasts
extracellular matrix of bone made up of
45% hydroxyapatite crystals (calcium phosphate), 35% collagen, 20% water
what are the minerals in bone for
make bones stiff, able to support structures, high strength under compression
what is collagen in bone for
gives bone some flexibility, reduces risk of fracture, high strength under tension
membrane on bones
periosteum, endosteum
what structures do bones contain
cortical bone, trabecular bone, blood vessels, medullary cavity, bone marrow, membranes
How does bone turnover work
osteoclasts on surface break down bone by releasing acids from ruffled border creating a resorption pit, osteoblasts build up again and produce bone matrix (osteoid unmineralised) and then initiate calcification. osteoblasts become osteocytes
where do osteocytes stay
lacunae connected by canaliculi which allows communication between cells
what type of collagen is in EM of bone
type 1
diseases where bone turnover doesn’t work
osteoporosis too much resorption, pagets disease too much resorption and formation, osteopetrosis not enough resorption
ossification
bone formation
types of ossification
endochondral and intramembranous. most bones are formed by combination of both
endochondral ossification
bone forms as cartilage model first then blood vessels invade the cartilage, cartilage is replaced with bone and the cartilage remains in epiphyseal growth plate and then growth plate eventually ossifies
intramembranous ossification
mesenchymal cells develop into osteoprogenitor cells that mature into osteoblasts. found in periosteum and endosteum. residual mesenchymal cells develop blood vessels and bone marrow. occurs in adults too
two types of bone growth
appositional and interstitial
appositional growth
osteoblasts on outside and osetoclasts on inside
