W:Ok,lastnightyouweresupposedtoreadanarticleabouthumanbones.Arethereanycommentsaboutit?
M:Well,tobeginwith,Iwassurprisedtofindouttherewassomuchgoingoninbones.Ialwaysassumedtheywereprettylifeless.
W:Well,that’sanassumptionmanypeoplemake.Butthefactisthatbonesaremadeofdynamiclivingtissuethatrequirescontinuousmaintenanceandrepair.
M:Right.That’soneofthethingsIfoundsofascinatingaboutthearticle---thewaythebonesrepairthemselves.
W:Ok.Socanyoutellushowthebonesrepairthemselves?
M:Sure.See,therearetwogroupsofdifferenttypesofspecializedcellsinthebonethatworktogethertodoit.Thefirstgroupgoestoanareaofthebonethatneedsrepair.Thisgroupofcellsproducesthechemicalthatactuallybreaksdownthebonetissue,andleavesaholeinit.Afterthatthesecondgroupofspecializedcellscomesandproducesthenewtissuethatfillsintheholethatwasmadebythefirstgroup.
W:Verygood.Thisisaverycomplexprocess.Infact,scientistswhostudyhumanbonesdon’tcompletelyunderstandityet.Theyarestilltryingtofindouthowitallactuallyworks.Specifically,becausesometimesafterthefirstgroupofcellsleavesaholeinthebonetissue,forsomereason,thesecondgroupdoesn’tcompletelyfillinthehole.Andthiscancauserealproblems.Itcanactuallyleadtoadiseaseinwhichthebonebecomesweakandiseasilybroken.
M:Ok,Igetit.Soifthescientistscanfigureoutwhatmakesthespecializedcellswork,maybetheycanfindawaytomakesurethesecondgroupofcellscompletelyfillstheholeinthebonetissueeverytime.That’llpreventthediseasefromeveroccurring.
Questions22to25arebasedontheconversationyouhavejustheard.
22.Whatistheconversationmainlyabout?
23.Whatisthefunctionofthefirstgroupofspecializedcellsdiscussedintheconversation?
24.Whatdoesthewomansayaboutscientistswhostudythespecializedcellsinhumanbones?
25.Accordingtotheman,whatisoneimportantpurposeofstudyingspecializedcellsinhumanbones?
