midterms L6

Question 1

how many bones in the body and what is it made out of

Answer 1

206 bones
organic matrix ( 35%)
inorganic elements (65%)
calcium hydroxyapatite

Question 2

what are the bone forming cells.

Answer 2

osteoblasts and osteocytes
first the osteoblasts predominate but when the skeleton reaches maturity, the actions of the osteoblasts and osteoclast are equal until the 3rd decade where the osteoclast predominates

Question 3

what are the 2 pathways after formation of a bone

Answer 3

direct - intramembranous ossification
tree-existing cartilage - endochondral ossification

Question 4

what are 3 bone diseases

Answer 4

achondroplasia & Thanatophoric ( dwarfism)
Osteogenesis Imperfecta ( brittle bone disease)
osteopetrosis

Question 5

achondroplasia & Thanatophoric (dwarfism)

Answer 5

• congenital disease transmitted as an autosomal dominant
• caused by defects in the cartilage synthesis at growth plates due to the mutation of FGFR3 located on short are of chromosome 4 causing short limbs.
• FGFR3 is a receptor w tyrosine kinase which transmits intracellular signals, signals transmitted by FGF3 inhibits the proliferation and function of growth plate chondrocytes so normal growth is suppressed
• normal inteligence, trunk and head almost normal sizee
• thanatophoric dwarf: lethal, extreme shortening of limbs, extreme small thorax so can be a cause of fatal respiratory disease

Question 6

how else can achondroplasia occur

Answer 6

as a sporadic mutation,
ppl w achondroplasia their membranous ossification is unaffected so skull, face, and axinal skeleton develop normally
- 4 main types of osteogenesis imperfecta occur w diff clinical manifestations classified according to severity of bone fragility
- FGFR3
-sclera appears blue because it is thin

Question 7

osteogenesis imperfecta (brittle bone disease)

Answer 7

congenital disease inherited autosomal dominant
many genes can be mutated
mutations occur in genes that encode for collagen type 1 production, causing too little bone so extreme skeletal fragility susceptible to fractures
- there is a defect in alpha 1 or alpha 2 chains of type I collagen, most fractures happen in diaphysis

type II OI’s feature: fatal in utero
type I features: blue sclera in both eyes, deformed teeth and hearing loss

Question 8

osteopetrosis

Answer 8

several forms of it
congenital and rare diseases
- caused by dysfunction of osteoclasts ( decrease in turnover rate)
- we ave failure of normal bone reabsorption by osteoclasts causing thickened dense bones ( deficiency in carbonic anhydrase)
increased risk of fractures, recurrent infections due to reduced bone marrow size and activity and anaemia and extra medullary hematopoiesis

Question 9

metabolic bone diseases

Answer 9

osteomalacia and rickets
pages disease of bones
hyperparathyroidism
osteoporosis

Question 10

osteomalacia and rickets

Answer 10

it is an acquired condition characterised by reduced bone mass, leading to bone fragility and susceptible to fractures osteomalacia in adults and rickets in children
we have abnormal calcification and we have mineralisation due to deficiency in vitamin D the causes are: malnutrition, malabsorption, renal diseases
it can be associated with ageing or in postmenopausal women
Rickets symt: big head, opened gap in skull suture, pseudo fracture