9. bone Flashcards


what is in the ECM of bone
Ground substance
- GAGs (Osteocalcin,sialoprotein)
- Minerals Ca++ PO42- - Hydroxyapatite
- Fibres*
- Type I collagen
osteoprogenitor cells
stem cells that form osteoblasts

obsteoblast
immature bone cells that secrete organic components of the matrix

osteocyte
mature bone cells formed from osteoblasts

osteoclasts
multinucleated macrophages acting as scavengers of unwanted material.

canaliculi
join lacunae together
filled with extracellular fluid
lacunae
spaces that hold osteocytes
Volkmann’s canal
connect Haversian canals
Haversians canals
gaps for blood vessels
periosteum
dense layer of vascular connective tissue surrounding bones
determines healing process
source of precursor cells: chondroblast and osteoblast
compact bone
dense bone organised into haversian systems
shaft of long bones corticol
spongy bones
bone organised into 3D netowrk of spicules with spaces- marrow cavity and ends of long bones- medullary
makes it lighter
what is needed for growth and maintenance of bone
mineralised matrix impermeable to water and small molecules
needs blood supply
growth by appositional (adding)
growth of lamellar bone, what is it formed from
osteoid-> woven-> lamellar
osteoid
newly formed matrix before mineralisation
woven
bone matrix with collagen arranged in random orientation
repair
lamellar bone
bone with collagen fibres arranged in parallel in alternating layers- adult bone
Intramembranous ossification
Bone islands - begin as bone in embryonic connective tissue (mesenchyme) from mesenchymal stem cells which differentiate into osteoprogenitor cells
These cells differentiate into osteoblast which start to form bony trabeculae
Trabeculae, which as they develop trap blood vessels, join together to form spongy bone, with osteoblasts at the surface laying down compact bone
endochondral ossification






which bones have endochondral ossification
Base of skull
Long Bones
Factors Influencing Bone Growth
mechanical forces
Nutrition
- Vitamin deficiencies
- Vitamin D reduced calcification
- Vitamin C collagen disrupted
- Vitamin A endochondral growth reduced
Hormones
- Growth hormone growth plate increases
- Adrenal androgens prepubertal growth spurt
- Gonadal steroids closure of epiphyses
- Thyroxine essential for osteogenesis
- Parathormone Ca from bone to plasma
- Oestrogen maintains bone density
Bone-derived Growth Factors: bone morphogenic protein