Bone Flashcards
what cells are found in bone?
- osteoprogenitor cells
- osteoblasts
- osteocytes
- osteoclasts
what are osteoprogenitor cells?
stem cell population
what is in the extracellular matrix of bone?
- collagen
- calcium hydroxyapatite
what do osteoprogenitor cells differentiate into?
osteoblasts
what is the appearance of osteoprogenitor cells?
flat, spindle shaped cells
closely applied to bone surface
what do osteoblasts originate from?
embryonic mesenchyme (osteoprogenitor cells)
what do osteoblasts secrete?
osteoid
what is osteoid?
unmineralised bone
where are osteoblasts found?
surface of bone
where are osteocytes found?
extracellular matrix
how to osteocytes connect to surrounding cells?
via canaliculi
how do osteocytes stay alive?
Oxygen and nutrients diffuse through canaliculi
what do osteoclasts originate from?
monocytes
what is the structure of osteoclasts?
mononucleate
where are osteoclasts found?
bone surface
what are Howship’s Lacunae?
depressions in the bone made by osteoclasts when they absorb it
how is the activity of osteoblasts and osteoclasts coordinated?
by a number of chemical messengers, e.g. RANK-Ligand
when does bone remodelling occur?
throughout life
what are the types of bone based on the pattern of collagen fibres within it?
- primary (woven)
- secondary (lamellar)
what are the types of ossification?
- membranous
- endochondral
what are the types of bone based on naked eye appearance?
- spongy/cancellous
- compact
what is another way of dividing bone types?
- osteons
- appositional
where is primary bone laid down?
- foetal bones
- fracture sites
what is the structure of primary bone?
- disorganised collagen fibre architecture
- mechanically weak
is primary or secondary bone stronger?
secondary
what is secondary bone formed as?
osteons
what are osteons?
- central Haversian canal containing a blood vessel
- surrounding concentric rings of lamellar bone with osteocytes
describe the composition of osteoid
- type I collage
- glycosaminoglycans
- proteoglycans
describe the composition of glycosaminoglycans
Includes compounds such as osteocalcin
- strong affinity for Ca2+
what bone is formed from deposition of parallel sheets?
lamellar
what bone is formed from deposition of haphazard bone?
woven
what stimulates osteoid mineralisation?
high local concentration of calcium & phosphate ions
what aids the mineralisation of osteoid?
osteocalcin
- binds Ca2+ and alkaline phosphatase
what is calcium deposited in bone as?
calcium hydoxyapatite
what type of bone does intramembranous ossification form?
- flat skull bones
* some cortical bone shafts
what is intramembranous ossification?
Formation of bone from a membranous precursor
when does intramembranous ossification begin?
2nd trimester of embryonic life
which type of ossification uses a cartilaginous pro forma?
endochondral
what is endochondral ossification?
Converts hyaline cartilaginous template into bone
what is the synovium?
Specialised tissue that lines the inside of the synovial joint capsule
what are synovial joints lined by?
hyaline cartilage on the articular surface
what are the types of synovial cell?
- type A
- type B
what are type A synovial cells?
phagocytes
what are type B synovial cells?
- rich in rER
* secrete synovial fluid
how many layers of synovial cells does synovium have?
1-4
describe the structure of synovium
- variable shapes
- squamous to cuboidal
- richly vascular
- highly innervated
