what are the 3 primary functions of bone?
- provide support where rigidity is needed eg// levers for locomotion, protection
- houses haemopoietic tissue
- calcium homeostasis
what are the 3 classifications of bones? give examples
- long bones - limbs eg/ femur
- flat bones - skull
- short bones - vertebrae
fill in the blanks; ALL bones are comprised of _______ bone and _______ bone
a) cortical bone
b) trabecular bone
describe cortical bone
dense compact bone
describe trabecular bone
cancellous, porous network for marrow
what is the periosteum?
connective tissue covering the outer surface of bone EXCEPT at articular surfaces
what is the endosteum?
all surfaces within the bone
describe the regions of long bones incl. what kind of bone is found within the region
epiphysis; each end of bone - trabecular bone, + thin shell of cortical bone
metaphysis; b/w diaphysis and epiphysis - transition frmo mostly cortical to mostly trabecular
diaphysis; shaft region - cortical bone only
what are the three arteries supplying the bone?
nutrient artery
metaphysical arteries
epiphyseal arteries
where does the nutrient artery enter the bone?
through the nutrient foramen in the SHAFT
the epiphyseal and metaphyseal vessels anastomose in a mature lamellar bone, why do they not in an immature woven bone?
obstruction by cartilage growth plate
where do venues in the cortical bone drain to?
periosteum
bone tissue is composed of?
cells and mineralised extra-cellular matrix
what does the bone matrix contain?
- type I collagen
- glycoproteins - bind calcium
- hydroxyapatite
how is the collagen within the bone matrix organised in lamellar vs woven bone?
lamellar = organised in layers woven = disorganised
LIST the bone cells
- osteoblasts
- osteoclasts
3.osteocytes - bone lining cells
+ blood vessels; endothelium & bone marrow; haemopoietic + adipose cells
what is an osteoblast? what does it secrete?
- cuboidal bone forming cell on tissue surface, secrete OSTEOID = mineralised
what is an osteocyte? where do they sit within the bone and what is their function?
- mature osteoblast, found in lacunae surrounding been matrix they secreted
- fine processes extending into canaliculi, forming tight junctions w/ other osteoblasts and -cytes.
- function in detecting mechanical strain
what is a bone lining cell?
flat cell, capable of diff into osteoblast on surface
what is an osteoclast? what is there function? are they present in large numbers?
- large multinucleate cell
- sparsely scattered// not many
- secrete H+ and lysosomal enzymes = DEGRADE bone matrix
how is cortical bone organised?
- into harvesian systems (osteons)
what are harvesian systems? how are they linked?
- longitudinal cylinders consisting of concentric bone lamellae surrounding central blood vessels
- linked to each other by transverse volkman’s canals
what are osteoblasts, bone lining cells and osteocytes derived from?
mesenchymal stem cells
what happens to an osteoblast once it has stopped secreting osteoid?
- differentiates into osteocytes or bone lining cells
OR - apoptosis
