The Skeletal System Name:_________________________________________Class:__________Date:____________

Vocabulary

Term Definition

bone marrow Softconnectivetissueinspongybone;makesbloodcells.cartilage Denseconnectivetissuethatprovidesasmoothsurfaceforthemovementofbonesat

joints.compact bone Denseouterlayerofbonethatisveryhardandstrong.growth plate Areaofgrowingtissueneartheendsofthelongbonesinchildrenandadolescents.ligament Bandoffibrousconnectivetissuethatholdsbonestogether.periosteum Tough,fibrousmembranethatcoverstheoutersurfaceofbone.skeletal system

Allthebody'sbones,cartilage,andligaments.

spongy bone Light,porousinnerlayerofbonethatcontainsbonemarrow.

Are bones alive? Fromseeingaskeleton,youmightthinkthatbonesarejustdead,hollowstructures.Butinalivingperson,thosehollowspacesarefulloflivingcells.Boneshaveabloodsupplyandnerves.Bonesarealivingtissue.

Your Skeleton Howimportantisyourskeleton?Canyouimagineyourbodywithoutit?Youwouldbeawobblypileofmuscleandinternalorgans,andyouwouldnotbeabletomove.Theadulthumanskeletonhas206bones,someofwhicharenamedbelow(Figurebelow).Bonesaremadeupoflivingtissue.Theycontainmanydifferenttypesoftissues.Cartilage,adenseconnectivetissue,isfoundattheendofbonesandismadeoftoughproteinfibers.Cartilagecreatessmoothsurfacesforthemovementofbonesthatarenexttoeachother,likethebonesoftheknee.Ligamentsaremadeoftoughproteinfibersandconnectbonestoeachother.Yourbones,cartilage,andligamentsmakeupyourskeletalsystem.Theskeletalsystemismadeupofbones,cartilage,andligaments.Theskeletalsystemhasmanyimportantfunctionsinyourbody.Whatbonesprotecttheheartandlungs?Whatprotectsthebrain?

Functions of Bones Yourskeletalsystemgivesshapeandformtoyourbody,butitalsoplaysotherimportantroles.Themainfunctionsoftheskeletalsysteminclude:Support.Theskeletonsupportsthebodyagainstthepullofgravity,meaningyoudon'tfalloverwhenyoustandup.Thelargebonesofthelowerlimbssupporttherestofthebodywhenstanding.Protection.Theskeletonsupportsandprotectsthesoftorgansofthebody.Forexample,theskullsurroundsthebraintoprotectitfrominjury.Thebonesoftheribcagehelpprotecttheheartandlungs.Movement.Bonesworktogetherwithmusclestomovethebody.Makingbloodcells.Bloodcellsaremostlymadeinsidecertaintypesofbones.Storage.Bonesstorecalcium.Theycontainmorecalciumthananyotherorgan.Calciumisreleasedbytheboneswhenbloodlevelsofcalciumdroptoolow.Themineral,phosphorusisalsostoredinbones.Structure of Bones

Bonescomeinmanydifferentshapesandsizes,buttheyareallmadeofthesamematerials.Bonesareorgans,andrecallthatorgansaremadeupoftwoormoretypesoftissues.Thetwomaintypesofbonetissuearecompactboneandspongybone.1.Compactbonemakesupthedenseouterlayerofbones.2.Spongyboneisfoundatthecenteroftheboneandislighterandmoreporousthancompactbone.Boneslooktough,shiny,andwhitebecausetheyarecoveredbyalayercalledtheperiosteum.Manybonesalsocontainasoftconnectivetissuecalledbonemarrowintheporesofthespongybone.Bonemarrowiswherebloodcellsaremade.

Bone Growth Earlyinhumandevelopment,theskeletonconsistsofonlycartilageandotherconnectivetissues.Atthispoint,theskeletonisveryflexible.Asthefetusdevelops,hardbonebeginstoreplacethecartilage,andtheskeletonbeginstoharden.Notallofthecartilage,however,isreplacedbybone.Cartilageremainsinmanyplacesinyourbody,includingyourjoints,yourribcage,yourears,andthetipofyournose.Ababyisbornwithzonesofcartilageinitsbonesthatallowgrowthofthebones.Theseareas,calledgrowthplates,allowthebonestogrowlongerasthechildgrows.Bythetimethechildreachesanageofabout18to25years,allofthecartilageinthegrowthplatehasbeenreplacedbybone.Thisstopsthebonefromgrowinganylonger.Eventhoughbonesstopgrowinginlengthinearlyadulthood,theycancontinuetoincreaseinthicknessthroughoutlife.Thisthickeningoccursinresponsetostrainfromincreasedmuscleactivityandfromweight-liftingexercises.Review

1. Arebonesalivingorgan?2. Whatarethethreecomponentsoftheskeletalsystem?3. Listfourfunctionsoftheskeletalsystem.4. Nameanddescribethetwotypesoftissuethatmakeupabone.