Bone structure and type

types of bone, structure of bones

1. Bone Structure and
Types
Sukhbir Kaur

2. Introduction:
•Bone:Itisarigidorganthatconstitutespartofthevertebrate
skeleton.
•Function:Tosupportandprotectthevariousorgansofthebody.
•Bonescomeinavarietyofshapesandsizesandhaveacomplex
internalandexternalstructure.
•Theyarelightweightyetstrongandhard,andserve
multiplefunctions.
•Inthehumanbodyatbirth,thereareover270bones,butmany
ofthesefusetogetherduringdevelopment,leavingatotalof206
separatebonesintheadultnotcountingnumerous
smallsesamoidbones.
•Thelargestboneinthebodyisthefemurorthigh-bone,andthe
smallestisthestapesinthemiddleear.
•Bonetissueisahardtissue,atypeofdenseconnectivetissue.It
hasahoneycomb-likematrixinternally,whichhelpstogivethe
bonerigidity.

3. Bone Structure
ØMatrix:Itismadeupof(90and
95%)collagenfibers,andtheground
substance.Itiscomposedoforganicand
inorganicmatter.
vInorganiccomponentismadeup
ofhydroxyapatitecrystals(thisisthebone
mineralthatgivesbonestheirrigidityand
tensilestrength)and
vOrganiccomponentcollagen,anelastic
proteinwhichgivescompressivestrength.
Thecollagenofboneisknownasossein.
ØBoneisformedbythehardeningofthis
matrixaroundentrappedcells.

4. Bone Tissue and Composition
•Bonetissue,orosseoustissue,isthe
majorstructuraland
supportiveconnectivetissueofthe
body.
•Bonetissueformstherigidpartof
thebonesthatmakeuptheskeleton.
•Bonetissuerefersspecificallyto
thebonemineralmatrixthatformsthe
rigidsectionsoftheorgan,andthe
bonecellswithinit.
•Therearethreetypesofbonetissue:
corticalbone,cancellousboneand
subchondralbone.

5. Types of Bone Tissue
1.Cortical Bone
•Thehardouterlayerofbones
composedofcorticalbonealso
calledCOMPACTBONE.
•Corticalreferringtotheouter
(cortex)layer.Thehardouterlayer
givesboneitssmooth,white,and
solidappearance,andaccountsfor
80%ofthetotalbonemassofan
adulthumanskeleton.

6. Alsoknownastrabecularor
spongybonetissue,istheinternal
tissueoftheskeletalboneandis
opencellporousnetwork.Thin
formationsofosteoblastscovered
inendosteumcreateanirregular
networkof
spaces,knownastrabeculae.
Withinthesespacesarebone
marrowandstemcellsthatgive
risetoplatelets,RBC’sand
WBC’s.
2.Cancellous Bone

7. 3.Subchondralbone/tissue
•Subchondralbone”isbonethatsits
underneathcartilageinajoint.
Subchondralboneisfoundinlarge
jointslikethekneesandhips,aswell
asinsmalljointslikethoseofthe
handsandfeet.
•Thisisthesmoothtissueattheendsof
bones,whichiscoveredwithanother
typeoftissuecalledcartilage.
•Thefunctionofthesubchondralbone
istoattenuateforcesgenerated
throughlocomotion,withthe
compactsubchondralboneplate
providingfirmsupportandthe
subchondraltrabecularcomponent
providingelasticityforshock
absorptionduringjointloading.

8. Osteon and Structure Of Cortical Bone
•Corticalboneconsistsofmultiple
microscopiccolumns,eachcalled
anosteon.
•Itconsistsofconcentricringscalled
lamellaewhichareformedbythe
osteoblaststhateventuallydifferentiate
intoosteocytes.Theseosteocytesare
locatedalongthelamellaeinspaces
calledLacunae.
•Inthecentreoftheosteonisacanal
calledtheHaversiancanal.Thiscontains
thebloodvessels,lymphvesselsand
neurons.

9. •Bonecontainsmanyofthese
individualosteons.Theadjacent
Haversiancanalsofthese
osteonsareconnectedby
Volkmann’scanals.
•Thecolumnsaremetabolically
active,andasboneis
reabsorbedandcreated,the
natureandlocationofthecells
withintheosteonwillchange.

10. Bonemarrowistheflexibletissueintheinterior
ofbones.Inhumans,redbloodcellsareproducedby
coresofbonemarrowintheheadsoflongbonesina
processknownashaematopoiesis.
Bonemarrowisalsoakeycomponentof
thelymphaticsystem,producingthelymphocytesthat
supportthebody’simmunesystem.
•Thetwotypesofbone
marroware"red
marrow“,whichconsists
mainly
ofhaematopoeitictissue
and"yellowmarrow“,
whichismainlymadeup
offatcells.
RBC’s,platelets,and
mostwhitebloodcells
ariseinredmarrow.Both
typesofbonemarrow
containnumerousblood
vesselsandcapillaries.
Bone marrow

11. BoneMarrow
•Alsoknownasmyeloidtissue,red
bonemarrow,canbefoundinalmost
anybonethatholdscancelloustissue.
•Innew-borns,allsuchbonesare
filledexclusivelywithredmarrow
orhaematopoieticmarrow.
•Inadults,redmarrowisfound
mainlyintheflatbones,suchas
thepelvis,sternum,
cranium,ribs,vertebraeandscapula,
andinthecancellousmaterialat
theepiphysealendsoflongbones
suchasthefemurandhumerus.

12. Atbirth,allbonemarrowsarered.Withage,moreandmoreofitisconvertedtotheyellow
type;onlyaroundhalfofadultbonemarrowisred.
Yellowmarrowisfoundinthemedullarycavity,thehollowinteriorofthemiddleportionof
longbones.
Incasesofseverebloodloss,thebodycanconvertyellowmarrowbacktoredmarrowto
increasebloodcellproduction.

13. FunctionoftheBonecellsistoworkinharmonyto
maintainabalancebetweenboneformationand
resorption,ultimatelytocontrolbonestructureand
function.Theyareresponsibleforthegrowing,shaping,and
maintenanceofbones.
4types:
•Osteoblast:Itisfoundinthegrowingportionsofbone,
includingendosteumandperiosteumandisresponsible
forformingnewbone.
•Osteoclast:Osteoclastsarethecellsresponsibleforbone
resorption,thustheybreakdownbone.Osteoclastsare
largecellswithmultiplenucleilocatedonbonesurfaces.
•Osteocyte:Maintainmineralconcentrationofmatrix.
•Osteoprogenitorcells:Developintoosteoblasts.
Boneisconstantlyremodelledbytheresorptionof
osteoclastsandcreatedbyosteoblasts.
Types of Bone Cells and their functions

14. Bone Cells :^I
•Bone is a metabolically active tissue composed of several types
of cells.
•Osteoblastsare mononucleate bone-forming cells. They are
located on the surface of osteon seams and make aproteinmixture
known asosteoid, which mineralizes to become bone.
•Osteocytesare mostly inactive
osteoblast.Theyoriginate from
osteoblasts that have migrated
into and become trapped and
surrounded by bone matrix that
they themselves produced.The
spaces they occupy are known
aslacunae.

15. There are five types of bones in the human body: Long, Short, Flat, Irregular, and Sesamoid.
TYPES OF BONES

16. Types of Bones
1.Longbonesaremuchlongerthan
theyarewide.Theyconsistof3
differentsections
•Epiphysis-containsspongyboneor
cancellousboneandalsocontainred
bonemarrowthatsynthesiseRBC’s.
•Metaphysis-containsanimportant
sectioni.e.Epiphysealplate
responsibleforlengtheningand
elongatinglongboneasorganism
actuallygrows.
•Diaphysis-long,curvedshaftthat
containscompactbonethatis
responsibleforgivingbone,its
strongness.

17. Theyarecapableofresistingvery
hightensileandcompressiveforces
duetowhichlongbonessupport
majorityofourbody’sweight.We
havemanydifferenttypesoflong
bonesinourbody.
Example:i)Clavicle(collarbone)
ii)Humerus,radius,ulna(arm)
iii)Femur,tibia,fibula(leg)
iv)Metacarpals
Long Bone (cont...)

18. 2.Shortbonesareroughlycube-shaped,andhaveonlya
thinlayerofcompactbonesurroundingaspongyinterior.
Theyareaslongaswide.Theyfunctionbyproviding
supportaswellasstabilitytootherbones.Theyarelocated
atthewrist(carpals)andankle(tarsals).
3.Flatbonesarethinandgenerallycurved,withtwo
parallellayersofcompactbonessandwichingalayerof
spongybone.Theyhavealargesurfacearea.
They:a)protectourinternalorgansandtissue
b)Serveasattachmentpointformusclebecauseoftheir
largesurfacearea.
Example:i)Skull(cranium)-flatbonesfuseheretoprotect
ourbrain.
ii)RibcageandSternum-thisactsnotonlyasattachment
pointofmusclebutalsoprotectheart,lungsandvascular
tissueinthisregion.
iii)Scapula(shoulderbladebone)
iv)Pelvis(hipbone)

19. 4.Sesamoidbonesarebonesembeddedin
tendons.Thisboneisinshapeofsesameseed.
ExampleofsesamoidboneisPatella(kneecap).
5.Irregularbonesdonotfitintotheabove
categories.Theyconsistofthinlayersofcompact
bonesurroundingaspongyinterior.Asimpliedby
thename,theirshapesareirregularand
complicated.Thus,theyhaveauniqueshapeand
function.Theyhelpinprotectionandsupportof
body.
Example:i)Maxilla(upperjawbone)and
Mandible(lowerjawbone)-theyhelptoeatand
ingestfood.
ii)Sacrum
iii)Vertebrae(cervicalandlumbar)-theyare
responsibleforprotectingourspinalcord.

20. Bonesconsistoflivingcellsembeddedinamineralizedorganicmatrix.
Thismatrixconsistsoforganiccomponents,mainlyTypeICollagen–
"organic"referringtomaterialsproducedasaresultofthehumanbody–
andinorganiccomponents,primarilyhydroxyapatiteandothersalts
ofcalciumandphosphate.Thecollagenfibersgiveboneitstensilestrength,
andtheinterspersedcrystalsofhydroxyapatitegiveboneitscompressive
strength.
Collagenconsistsofstrandsofrepeatingunits,whichgivebonetensile
strength,andarearrangedinanoverlappingfashionthatpreventsshear
stress.Thefunctionofgroundsubstanceisnotfullyknown.
Twotypesofbonecanbeidentifiedmicroscopicallyaccordingtothe
arrangementofcollagen:
Wovenandlamellar.

21. Woven Bone
Wovenbone,(alsoknown
asfibrousbone)whichis
characterizedbyahaphazard
organizationofcollagenfibersthat
occursinitiallyinallfetalbones.It
ismechanicallyweaker,witha
smallernumberofrandomly
orientedcollagenfibers,butforms
quickly;itisforthisappearanceof
thefibrousmatrixthattheboneis
termedwoven.Itissoonreplaced
bylamellarbone.
Afterafracture,wovenboneforms
initiallyandisgraduallyreplacedby
lamellarboneduringaprocessknown
as"bonysubstitution."Comparedto
wovenbone,lamellarboneformation
takesplacemoreslowly.

22. Ithasaregularparallelalignmentof
collagenintosheets("lamellae")and
ismechanicallystrong.Itishighly
organizedinconcentricsheetswitha
muchlowerproportionofosteocytes
tosurroundingtissue.Itmakesits
firstappearanceinhumansin
thefetusduringthethirdtrimester,is
strongerandfilledwithmany
collagenfibersparalleltoother
fibersinthesamelayer(these
parallelcolumnsarecalledosteons).
LamellarBone

23. Thank you