boe function and repair Flashcards
what are the functions of bone
mechanical- form basis of levers
synthetic - haemopoesis
metabolic - stores mineral (ca2 and P), fats and is involved in acid base homeostasis
descrive intramembranous ossification
for development of flat bones, takes place in mesenchymal tissue
1) mesenchymal stem cells form a tight cluster and begin to transform into osteoproginitor cells and then into osteoblasts
2) osteoblasts lay down osteoid
3) osteoid mineralises to form the spicules
4) spicules join to form trabeculae which merge to form woven bone
5) trabeculae replaced by lamellae of mature compact bone
difference between mature and immature bone
osteocytes are in random arrangements in immature bone and in mature bone they are arranged in the lamellae of osteons
how does bone have tensile and compressible strength
main force lines go thorough cortical bone and lamellae are able to slip relative to each other to resist fracture. also has degree of flexibility
how do bones remodel themselves
bone is absorbed by osteoclasts and put down where needed by osteoblasts by appositional growth. inactivity will increase bone resorption and therefore bone strength all decrease
factors affecting bone stability
osteoid recycling - osteocytes act like osteoblasts and lay down osteoid in their lacunae
bone deposition - activity of osteoblasts stimulated by calcitonin, testosterone, oestrogen, thyroid hormones and vitamin A
bone resorption - activity of osteoclast increased by PTH, releases calcium into blood. Effect of this hormone is blocked by calcitonin
vitamins important for bone stability
vitamin D- produces calcitriol used is calcium absorption
vitamin C - synthesis of collagen
vitamin K - synthesis of bone proteins
explain the process of fracture repair
1) clot forms
2) neutrophils/macrophages and osteoclasts remove dead tissue
3) formation of granulation tissue with capillaries
4) fibrocarteagenous formation- fibroblasts lay down collagen and chondroblasts lay down hyaline cartilage
5) endo and intra ossification lay down cancellous and compact bone
6) bone remodelling take place - back to before
how does bone remodelling work
osteoclast make wide tunnel called cutting cone and osteoblasts make smaller tunnel of cortical bone called closing tunnel
what is osteogenesis imperfecta
mutation in a gene meaning incorrect production of collagen fibres results in weak bones and shortened stature
what is rickets
vitamin D deficiency affecting children. Poor calcium mobilisation and ineffective mineralisation results in weak bone. soft bones, painful to walk and shortened height
what is osteomalacia
a vitamin D deficiency in adults resulting in lower mineralisation and increased osteoid meaning its not as strong as it should be.
due to kidney disease (would usually activate vit D), covering up from sun, surgery or drugs that prevent vit D absorption
what is primary osteoporosis
type 1
occurs in postmenopausal women due to increased osteoclast number
type 2
occurs in both men and women due to loss of osteoblast function
what is secondary osteoporosis
results of drug therapy resulting in affected bone remodelling and therefore bone loss
also caused by bone metabolic bone diseases
how does osteoporosis happen
incomplete filling of osteoclast resorption bays resulting in vertebral compression and loss of bone tissue. gives hunched back
