bone Flashcards
what does the axial skeleton consist of
skull
vertebral column
thoracic cage
what does the appendicular skeleton consist of
the upper and lower extremities, which include the shoulder girdle and pelvis.
what are the functions of bone
mechanical- protecting vital organs , form basis of levers for movement , provides framework for overall shape of human body
synthetic- haemopoiesis
metabolic- mineral storage (calcium and phosphorus ), fat storage and acid base homeostasis ( absorbs or releases alkaline salts to help regulate blood pH)
what are the two kids of bone tissue
cancellous (spongy)
compact (dense)
what is the thin cellular layer lining the marrow cavity called
endosteum
where is compact bone found
shafts of long bone and forms the plates of flat bone
where is spongy bone found
end of long bone and centre of flat and irregular bones
what are the two types of ossification
endochondral ossification- formation of long bones from a cartilage template. continued lengthening by ossification at epiphyseal plate. appositional growth
intra-membranous ossification- formation of bone from clusters of mesenchymal stem cells in the centre of bone. interstitial growth. flat bone use this
what is the function of compact bone
provides mechanical strength and protection of underlying organs
function of cancellous bone
provides space for red marrow to grow and develop. yellow bone marrow is also found here. this contains adipose tissue and acts as an energy source
what about the bone’s extracellular matrix gives it rigidity and hardness
impregnated with mineral salts-mainly calcium phosphate
what is different about sesamoid bones compared to other bones
not covered in periosteum
how is periosteum attached to bone
by collagen fibres called sharpey’s fibres
describe the structure of the periosteum
2 layers
outer layer is dense collagenous connective tissue with blood vessels, nerves and a few fibroblasts
inner layer: more loosely arranged. less vascular. provides the sharpey’s fibres. contains osteoprogenitor cells that differentiate into osteoblasts. called osteogenic layer.
what is the cement line
zone where newly formed osteoid meets original/existing bone
how does cancellous bone become compact bone
1) MSC convert into osteoblast that line trabeculae.
2) Lay down osteoid that is mineralised
3) Osteoblasts become trapped and are now osteocytes.
4) This is repeated
5) Central MSC covert into blood vessels, lymph vessels and nerves
role of canaliculi
provide channels through which travel the cytoplasmic processes of osteocytes that form gap junctions with neighbouring cells.
also transports waste products to the vasculature
what lines the lacunae and canaliculi
sheath of Neumann
what is at the centre of osteons and what does this carry
Haversian canal
carry nutrient providing blood vessels, lymphatic vessels and nerves
how do haversian canals communicate with marrow cavity, periosteum and each other
volkmann’s canals
difference between immature and mature bone
immature has osteocytes in random arrangements and mature has them arranged in concentric lamellae of osteons
what are the lacunae
spaces occupied by osteocytes
difference between cancellous and compact bone
cancellous is not made of osteons but of trabeculae.
no canals in cancellous
no nerves, blood vessels or lymphatic vessels in cancellous
why can bone resist fracture
great tensile and compressive strength. a degree of flexibility
different layers of lamellae can slide across each other. cells have h20 that resist compression
what is a key determinant of bone strength
exercise
describe bone remodelling
osteoclasts make a wide tunnel in bone. they use enzymes and acids to breakdown bone changing the bone into osteoid and release the osteocytes on the bone making them osteoblasts.
osteoblasts can make a small tunnel of bone
factors affecting bone stability
ageing-decrease of oestrogen and testosterone . these hormones would normally suppress the proliferation and actions of osteoclasts causing increased resorption when levels are diminished.
neoplasia- benign tumours (chondroma & osteoma), malignant tumour (chondrosarcoma & osteogenic sarcoma)
disorders- achondroplasia, rickets, osteomalacia,osteoporosis
what is osteogenesis imperfecta
brittle bone disease mutation of COL1A gene(affecting synthesis of type 1 collagen) weak bones increased risk of fracture shortened height and stature
what is rickets
vit D deficiency mainly affects children poor calcium mobilisation ineffective mineralisation weakened bone development soft bone shortened heigh and stature bowed legs
what is osteomalacia
‘rickets’ in adults
vit d deficiency
lower mineralisation
increased osteoid but isn’t turning into mineralised bone.
what happens in osteoporosis
loss of bone matrix, loss of structural density and demineralisation, increasing risk of fracture s
holes in trabecullae
who does osteoporosis primary type 1 occur in
postmenopausal women
due to increase in osteoclasts as a result of loss of oestrogen
who does osteoporosis primary type 2 occur in and why
older men and women
loss of osteoblast function
loss of both oestrogen and androgen
what is the cause of secondary osteoporosis
drug therapy (corticosteroids)
malnutrition
metabolic bone diseases e.g hyperparathyroidism
what is achondroplasia
inherited mutation in FGF3 receptor gene FGF promotes collagen formation from cartilage so endochondrial ossification is affected.
short stature
but normal sized head and torso
