L13 Ossif And Bone Dis Flashcards
LO1:
INTRAMEM:
-primit CT mesenchyme precedes bone dev. Bones dev part/wholly by this proc incl flat ones of skull. Occs within condensats of mesenchyme tiss, not repl hyal cartil. Eg flat bones of skull (parietal, occipital, tempor, frontal), maxilla, mandible, pelvis prob mixt, clavicle (medial end endoch, Lat intramem, is 1st bone start ossif, one of last to finish), scapula some endoch. Cont ribs to thicken not length. Apposit growth.
-small clust mesenchyme SC form tight clust=nidus MSCs become osteoprogen it cells-each dev incr Golgi and RER. Become osteoblasts and lay ECM cont T1 Coll=osteoid- Mineralises= rudim bone spicules surr by osteoblasts, cont osteocytes. Spicules join=trabec which merge=woven bone-repl by lamellae of compact bone event. Vasc mesenchyme tiss.
14wk fetus parietal- trabec radiate from cent pt. min deposit in trabec radiate out from prim ossif cent.
Compact bone dur post natal dev indisting from endoch ossified bone.
LO2: desc how morph and/or mech props of bone can change in dis.
LO3: expl role of abn in composit of bone ma and activ of bone cells in causing changes.
LO4: outl conseqs of 4 diff and contr bone dis for affected indiv and soc. Oseteogenesis imperf T1 Coll gene. Osteoporosis metab bone dis incr resorp. Achondroplasia GoF fibrob GFR3 gene. Rickets/osteomalacia if low vitD.
LO5: desc genet basis and histol changes in osteogenesis imperfecta, and poten medico legal imp.
-oseteogenesis imperfecta- autos domin grp hermit disorders of CT. mut in gene for T1 Coll. 1/10000. T1 Coll abund so affs skel, jnts, ears, ligs, teeth, sclerae, skin. T1-4 var severity and symps. Aff synth of T1 Coll dur ossif=bone brittle, prone fracture. Sev may= die bef birt, less sev= disab and deform.
Poss confus with delib inj. Frac calluses and bowing. Jnt displ=bone fus. Done deform, thin and atten.
-eff of sex horms on bone- infl dev of ossif centres. Androgens male, oestrog fem but both have both. They induce sec sex chars and cause pub growth spurt. Precocious sexual mat eg early pub (can be stim by sex horm prod tum) can cause premat closure/fus GP. If decr sex horm epiph plates may persist later=tall.
-eff of thyr horm on bone- delet effs of neonatal hypoth. Can Rev by thyroxine admin. If untreated=perman neurol dam (cretinism) and other abn eg short stature.
-lack GH from pit can aff epiph cartil=pit dwarfism. Incr GH can= incr growth long bones=gigantism. In ad GP fused so incr GH not incr length but may incr width=periosteal growth=acromegaly.
LO6: desc radiol and histol changes in osteoporosis. List comm RFs. Expl imp as frac risk in eld.
-OP aff 1/3 wom and 1/2 men over 50. Incr bone abs rel to format. Metab bone dis- min bone decr in mass to. Pt no longer provs adeq mech supp. Decr mass trabec partic relev to incr frac. Atten and weak. Osteoclasts breakd but not repl by osteoblasts calcif. Assoc with aging. Decr bone ma, struc dens= incr frac esp spine comp, hip, wrist. Eas detec by DEXA scan bone dens.
-bone mass peak 25-35 yr. decr 50-60s. USA 15% hip frac by 80, 25% by 90. 1.2m frac/yr. fatal complics 12-20%. In whites wom 2x risk hip frac as men. 8x risk verteb frac. Age and post menop loss main RFs. Prim OP T11 and 2 most comm.
T1 postmen op=incr osteoclasts no as decr oestrog.
T2 senile OP gen over 70, atten osteoblasts func.
Other RFs- genet- peak bone mass higher in balks.
Insuff diet Ca- recomm postmen op 800mg/d, Ca tabs often with vitD.
Insuff Ca abs and vitD- decr renal activat of vitD with age of not supplem or confined indoors.
Exercise- I mob of bone=incr loss, stress stim osetoblasts.
Smoking- in wom correl.
LO7: outl cause and morph feats of achondroplasia.
-comm form short limb dwarfism. 1/15000 LB. norm net and AV lifesp. Autos domin pt mut in fibrob GFR3 gene=GoF=incr endoch ossif, decr prolif chondroc in GP cartil, decr cell hypert, decr cartil ma prod= decr act of epiph GP.
Short limbs. Trunk often norm length. Vault of skull large. Face small. Flat nose. Over 80% par not have-is new mut. Mean ad height 131cm male, 125 fem. homoz die.
Epiph GP-narr plate, decr cartil prolif. Transverse barrs of bone seal off plate. Most prominent shorten proxim segm.
LO8: expl imp of vitD in norm bone dev.
- vit D metab- UV/diet to liver and kidn for hydroxylat and activ=incr bone remod, incr blood Ca. PTH also incr bone reabs and kidn reabs so incr blood Ca. PTH also incr vitD active format.
- most vitD synth in skin by UV act. Some diet. Both hydroxyl in liver=active 1,25 dihydroxyvitD3= incr Ca abs by SI and prom min of bone by osteoblasts. W/o vitD=poor min, pliable ma. Bones bend under weight. Also incr frac. In childhood growing bones are aff=rickets. Simil proc in ad-bones become pliable dur remod=osteomalacia eg if cant go outside/low vitD diet.
LO9: desc feats of bones aff by rickets and osteomalacia and diff btw them. Desc imp of diet and behav faces in prev both.
-rickets- kids. Bones not harden as vitD defic. Comm in Asian UK. UV/diet. Insuff Ca deposit. Esp long bones, soft and malf. Distort skull bone=bossing. Enlarge costs chondrobl juncs of ribs=rickety rosary.
-osteomalacia- sig Ca defic/lack vitD due to decr diet int, low UV expos, decr int abs, kidn/liv dis, decr hydroxylat vitD.
Comm symp- bone pain, back ache, musc weakn, no obv deform. Trabec lot unmin bone cav surf (osteoid)=weak. Insuff Ca stim. Cortic and trabec. Osteoid lay of trabec thicker. Norm amnt bone ma, decr min. OP is decr ma. Comm frac- nof, pubic Ramos, spine, ribs.
LO1: desc proc of intramem and endochondral ossif as rel to bone growth.
Both inv repl exist CT by bone- growth and diff.
ENDOCHONDRAL:
-repl exist hyaline cartil templ with bone. How most bones dev. Eg long bones in fetus-cartil epiphyses, bony diaphysis at 14wk. 14wk hyaline cartil mod precurs of most bones, subseq mineralisat. Dev long bones grow by endoch ossif. Cartil skel=reduc dam. Calcif diaphysis and metaphysics. Epiphyseal growth plates of hyal cartil in dev bone. Cartil to bone beneath GP=grow out from GP. GP long bone dissap after cessation growth.
-long bone dev by endoch ossif- 5-5 wk init small cartil mod. 6-8 wk collar of periosteal bone at edge of shaft. 8-12 wk cent cartil calcify, nutr art penet, supp oseteogenic cells, prim ossif centre formed in mid shaft. Postnatal medulla to cancel bone, cartil forms epiphys GPs, epiph devs secondary centres of ossif. GP calcif tow shaft. Prepubertal epiph ossify and GP contin move apart=lengthen bone. Mat ad epiph GP repl by bone. Hyal artic cartil persists.
Periosteal ossif=incr width is intramem.
-ext remod long bone- as shaft grows. Shaft elong as cartil grows under GP and repl by bone. Bone reabs and added to keep shape epiph. Epiph enlarges by growth of cartil and repl by bone. Epiph GP top of metaph. Cols of calcif cartile tx down from GP and become min.
-LS of epiph GP of infant long bone-
Top zone of reserve cartil-no cellul prolif by mitosis, or active ma prod.
Zone of prolif- chondroc div=cols, cells enlarge and sec ma. ECM forced. Btw cols.
Zone of hypertrophy- cells enlarge, cartil ma compressed to Lin bands btw cell cols.
Zone of calcif cartil- enlarged cells degen and ma calcify.
Zone of resorption- calcif ma direc contact marrow cav. BV and CT invade reg occupied by dying chondroc, leave calcif cartil as spicules btw them. Bone laid down on cartil spicules. Osteoclasts, blasts, BV and bone. Osteoid=non calcif bone, is precurs laid down by osteoblasts. Osteoclasts up to 5 nuc, formed by fus.
