Skeletal System.pdf

Tortora language point wise taken by book

1. Bones and Skeletal System
BY: Dr.Tanvi H. Desai
(M.Pharm, Ph.D)

2. Introduction
•Aboneismadeupofseveralbonetissuesbone,cartilage,denseconnective
tissue,epithelium,adiposetissue,andnervoustissue.
•Theentireframeworkofbonesandtheircartilagesconstitutestheskeletal
system.
•Movementssuchaswalkingrequireinteractionsbetweenbonesandmuscles.
•Thebones,muscles,andjointstogetherformanintegratedsystemcalledthe
musculoskeletalsystem.
•Thebranchofmedicalscienceconcernedwiththepreventionorcorrectionof
disordersatthemusculoskeletalsystemiscalledorthopedics(orthocorrect;
pedi=child).

3. Functions of bone and the skeletal system
Bonetissueconstitutesabout18%oftotalbodyweightandperformsseveral
basicfunctions.
1.Support:Itservesasthestructuralframework,supportssofttissuesand
providesattachmentforthetendonsofmostskeletalmuscles.
2.Protection:Theskeletonprotectsvitalinternalorgansfrominjury,eg,
cranialbonesprotectthebrain,vertebrae(backbones)protectsthespinal
cord,andtheribcageprotectstheheartandlungs.
3.AssistsMovement:Mostskeletalmusclesattachtobonesandbringabout
movementsbypullingduetotheircontraction
4.MineralHomeostasis:Bonesstoneseveralminerals,especiallycalciumand
phosphorus,whichstrengthenthebone.

4. Onbodydemand,bonereleasesmineralsintothebloodtomaintaincritical
mineralbalances(homeostasis)fordistributiontootherpartsofthebody.
5.BloodCellProduction:Redbonemarrow(aconnectivetissue)withincertain
bonesproducesRBCs,WBCsandplatelets,aprocesscalledhemopoiesis.
•Redbonemarrowconsistsofdevelopingbloodcells,fibroblasts,adipocytes,
andmacrophageswithinnetworkofreticularfibres.
•Itoccursindevelopingbonesofthefoetusandinsomeadultboneslikethe
pelvis,ribs,breastbone,vertebrae,skull,andendsofthebonesofthearm
andthigh.
•6.Triglyceridestorage:Yellowbonemarrowconsistsmainlyofadiposecells,
whichstoretriglycerides(foodreserve).

5. STRUCTURE OF BONE
•Atypicallongboneconsistsof
followingparts:
•1.Diaphysis(growingbetween):Itis
thebodyofthebone,whichislong,
cylindrical,mainportionofthebone.
•2.Epiphyses(growingover):Theseare
thedistalandproximalendsofthe
bone.

6. 3.Metaphyses(Between):Thesearetheregionsofmaturebonewherethediaphysisjoins
theepiphyses.
Ingrowingboneitrepresentstheepiphysealplate(alayerofhyalinecartilagethatallows
thegrowthofboneinlength).
Ataboutages18-21whenaboneceasestogrow,cartilaginousepiphysealplateisreplaced
bybone,nowcalledepiphysealline.
4.Articularcartilage:Itisathinlayerofhyalinecartilagecoveringthatpartofepiphysis
wherethebonearticulateswithanotherbone.
Itreducesfrictionandabsorbsshockatfreelymovablejoints.+

7. •5.Periosteum:Itisatoughsheathofdenseirregularconnectivetissuethat
surroundsthebonesurfacewherethereisnocartilage.
•Itsboneformingcellsenablebonetogrowinthickness,butnotinlength.
•Periosteumalsoprotectsthebone,assistsinfracturerepair,helpstonourish
bonetissue,andservesasanattachmentpointforligamentsandtendons.
•6.Medullarycavity(Marrowcavity):Itisthespacewithinthediaphysisthat
containsfattyyellowbonemarrowinadults.
•7.Endosteum:Itisathinmembranethatlinesthemedullarycavity.Itcontains
asinglelayerofboneformingcellsandasmallamountofconnectivetissue.

8. TYPES OF BONES
•Almostallbonesofthebodycanbeclassifiedintofivemaintypesbasedonshape:long,
short,flat,irregularandsesamoid
1.Longbones:Theyhavegreaterlengththanbreadth,consistofashaftandavariable
numberofextremities(ends),andareslightlycurvedforstrength.
•Longbonesconsistmostlyofcompactbonetissueintheirdiaphysisbuthaveconsiderable
amountsofspongybonetissueintheirepiphyses.
•Examples:Femur(thighbone),tibiaandfibula(legbones),humerus(armbone),ulnaand
radius(forearmbones),andphalanges(fingersandtoes).
2.Shortbones:Thesearesomewhatcubeshapedandnearlyequalinlengthandwidth.
•Theyconsistofspongybonetissuesurroundedbyathinlayerofcompactbonetissue.
•Examples:Carpalbones(exceptpisiform;sesamoid)andthetarsal(ankle)bones(except
calcaneousorhealbone;irregular).

9. 3.Flatbones:Theyaregenerallythinandcomposedoftwonearlyparallelplatesof
compactbonetissueenclosingalayerofspongybonetissue.
Examples:Cranialbones,thesternum(breastbone),ribs,andscapulae(shoulder
blades).
4.Irregularbones:Theyhavecomplexshapeandvaryintheamountofspongyand
compactbonetissue.
Examples:Thevertebrae(backbones),hipbones,certainfacialbones,andthe
calcaneous.
5.Sesamoidbones(bonelikeasesameseed):developincertaintendonswhere
thereisconsiderablefriction,tension,andphysicalstress,suchaspalmsandsoles
(fewmminsize).
Theyprotecttendonsfromexcessivewearandtear(ઘસારો).
Examples:Twopatellae(kneecaps),locatedinquadricepsfemoristendon.
Onthebasisoflocation,anadditionaltypeofsmallsuturalbonesarelocatedin
sutures(immovablejoints)betweencertaincranialbones.Theirnumberisvariable
frompersontoperson.

10. Divisions of the skeletal system
•Theadulthumanskeletonconsistsof206namedbones,mostofwhicharepaired(rightand
leftsidesofthebody).
•Theskeletonofinfantsandchildrenhavemorethan206bones(somefuselater,eg,hip
bonesandsomebonesofvertebralcolumn).
•Bonesoftheadultskeletonaregroupedintotwoprincipaldivisions:theaxialskeletonand
theappendicularskeleton.
•1.Theaxialskeletonconsistsofbonesarrangedalongthelongitudinalaxis(goingfrom
headtotail).
•Thepartsoftheaxialskeletonaretheskull,auditoryossicles(earbones),hyoidbone,
vertebralcolumn,sternum,andribs.
•2.Theappendicularskeletonconsistsofthebonesofthegirdlesandtheupperandthe
lowerlimbs.
•Thepartsoftheappendicularskeletonarepectoral(shoulder)girdles,bonesoftheupper
limbs,pelvic(hip)girdles,andbonesofthelowerlimbs.

12. AXIAL SKELETON
•1Skull
•Theskullissituatedontheupperendofvertebralcolumnanditsbonystructureisdividedintotwo
parts:
•Thecranium
•Theface
A.Cranium:Itisformedbyflatandirregularbonesthatprovideabonyprotectiontothebrain.
•Ithasabaseuponwhichthebrainrestsandavault(roof)thatsurroundsandcoversit.
•Inadults,thesuturesbetweenthebonesareimmovable.
•Theboneshavevariousperforations(gaps)suchasforaminaandfissures(narrowpassge)through
whichnervebloodandlymphvesselspasses.
•Thecraniumconsistof;
•1Frontalbone 2Parietalbones
•2Temporalbones 1Occipitalbone
•1Sphenoidbone 1Ethmoidbone

14. •Frontalbone:Itistheforeheadbone.
•Itformspartofeyesocketsandthenoticeablepoints
abovetheeyes,thesupraorbitalmargins.
•Justabovethesupraorbitalmarginswithinthebone,
therearetwoair-filledcavitieswhichhaveopeninginto
thenasalcavity.
•Thecoronalsuturejoinsthefrontalandparietalbones.
•Parietalbones:Thesebonesformthesidesandroofof
theskull.
•Theyarticulatewitheachotheratthesagittalsuture,
withthefrontalboneatthecoronalsuture,withthe
occipitalboneatthelambdoidalsutureandwiththe
temporalbonesatthesquamoussutures.

15. •Temporalbones:Theseboneslieoneoneachsideoftheheadand
formimmovablejointswiththeparietal,occipital,sphenoidand
zygomaticbones.
•Thesquamouspartarticulateswiththeparietalbone.
•Thezygomaticprocessarticulateswiththezygomaticbonetoformthe
zygomaticarch.
•Themastoidpartcontainsthemastoidprocess,athickenedportion
behindtheear.
•Thetemporalbonearticulateswiththemandibleatthetemporo-
mandibularjoint.
•Occipitalbone:Itformsthebackofheadandbaseofskull.
•Ithasimmovablejointswiththeparietal,temporalandsphenoid
bones.
•Sphenoidbone:Itoccupiesthemiddleportionofbaseofskullandit
articulateswiththeoccipital,temporal,parietalandfrontalbones.

16. •Ethmoidbone:Itoccupiestheanteriorpartof
baseoftheskullandhelpstoformtheorbital
cavity,thenasalseptumandthelateralwallsof
thenasalcavity.
•Itisverydelicatebonecontainingmanyair
sinusesthatopensintothenasalcavity.
•(B) Face:
•Thefaceisformedby13bonesinadditionto
thefrontalbone.
•Thisincludes;
•2Cheekbones 1Maxilla
•2Nasalbones 2Lacrimalbones
•1Vomer 2Palatinebones
•2Inferiorconchae 1mandible

17. •Cheekbones:Itformstheprominencesofthe
cheeks,partofthefloorandlateralwallsoforbital
cavities.
•Maxilla(Upperjawbone):Itformstheupperjaw,
theanteriorpartofroofofthemouth,thelateral
wallsofthenasalcavityandpartofthefloorof
orbitalcavities.
•Thealveolarprocessprojectsdownwardsand
carriestheupperteeth.
•Nasalbones:Thesearetwosmallflatboneswhich
formthepartofthelateralandsuperiorsurfaces
ofthenose.
•Lacrimalbones:Thesearesmallbonespresent
posteriorandlateraltothenasalbonesandform
partofthemedialwallsoftheorbitalcavities.

18. •Vomer:Itisathinflatbonewhichextendsupwards
fromthehardpalatetoformthenasalseptum.
•Palatinebones:ThesearetwoL-shapedbones.
•Thehorizontalpartsofbonesunitetoformposterior
partofhardpalateandtoformpartofthenasal
cavity.
•Inferiorconchae:Itisascroll-shapedbonewhich
formspartofnasalcavity.
•Thesuperiorandmiddleconchaearepartsofthe
ethmoidbone.
•Mandible:Itistheonlymovableboneoftheskull.
•Eachhalfconsistsoftwomainparts:acurvedbody
withthealveolarridgecontaininglowerteethanda
ramusprojectsupwardstotheposteriorendofthe
body.

19. •HyoidBone:Itisahorse-shoeshapedbonelying
intheneckjustbelowthemandible.
•Itdoesnotarticulatewithanyotherbonebutis
attachedtothestyloidprocessofthetemporal
bone.
•Itgivesattachmenttothebaseofthetongue.
•Sinuses:Sinusescontainingairarepresentinthe
sphenoid,ethmoid,maxillaryandfrontalbones.
•Theyallcommunicatewiththenasalcavityand
arelinedwithciliatedmucousmembrane.
•Itsfunctionsaretotonethevoiceandtoliftthe
bonesofthefaceandcranium.

20. Vertebral column
•Structures
•Thevertebralcolumn(spineorbackbone)iscomposedofaseriesofbonescalled
vertebrae.
•Thevertebralcolumn,thesternum,andtheribsformtheskeletonofthetrunkofthe
body.
•Thevertebralcolumnconsistsofboneandconnectivetissue;thespinalcordthatit
surroundsandprotectsconsistsofnervousandconnectivetissue.
•Theaveragelengthofvertebralcolumnisabout71cminadultmaleandabout61cmin
adultfemale.
•Thetotalnumberofvertebraeduringearlydevelopmentis33.
•Asachildgrows,severalvertebraeinthesacralandcoccygealregionsfuse.
•Thevertebralcolumnintheadulttypicallycontains26vertebrae.

21. •These are distributed as follows:
•7 cervical vertebrae (cervic-= neck) are in the neck region.
•12 thoracic vertebrae (thorax = chest) are posterior to the thoracic cavity.
•5 lumbar vertebrae (lumb-= loin) support the lower back.
•1 sacrum (= sacred bone) consists of five fused sacral vertebrae.
•1 coccyx (= cuckoo; resembles the bill of cuckoo bird) usually consists of four fused
coccygeal vertebrae.
•The cervical, thoracic, and lumbar vertebrae are movable, but the sacrum and
coccyx are not.

23. •FunctionsofVertebralColumn
•Itfunctionsasastrong,flexiblerodwithelementsthatcanmoveforward,backward,and
sideways,andcanrotate.
•Itformstheaxisonwhichbodyweightisreceived.
•Allthemovablevertebraehaveacanalinthemandallarearrangedinsuchawaythat
theymakeonecontinuouspassageorneuralcanalthroughwhichthespinalcordruns
fromheadtotail.
•Itprovidesprotectiontothespinalcord.
•Thefirstvertebra(atlas)articulateswiththeskullanditprovidessupporttoheadaswell
asitsup-downandsidewaymovements.
•Itservesasapointofattachmentfortheribs,andtogethertheyprotectthevitalorgans
likeheartandlungs.
•Italsoprovidesapointofattachmenttopelvicgirdleandmusclesoftheback.
•Manyinternalorgansgetsupportorsuspensionwithit

24. •Intervertebral Discs
•Intervertebraldiscsarefoundbetweenthe
bodiesofadjacentvertebraefromthesecond
cervical(C₂)vertebratothesacrum.
•Eachdischasanouterfibrocartilaginousring
(annulusfibrosus)andaninnersoft,pulpy,
highlyelasticsubstancecallednucleuspulposus.
•Thediscsformstrongjoints,permitvarious
movementsofthevertebralcolumn,andabsorb
verticalshock.
•Undercompression,theyflattenandbroaden
withage,nucleuspulposushardensand
becomeslesselastic.

25. •PartsofaTypicalVertebra:
•Vertebraetypicallyconsistofabody,avertebralarch,and
severalprocesses.
1.Body:Itisthick,discshaped,weightbearinganterior
partofavertebra.
•Itssuperiorandinferiorportionsareroughnedforthe
attachmentofdiscs.
•Theanteriorandlateralsurfacescontainnutrientforamina
openingsthroughwhichbloodvesselsdelivernutrients
andoxygenandremovecarbondioxideandwastesfrom
bonetissue.
2.Vertebralarch:Twoshort,thickprocesses(pedicles:a
smallstalklikestructureconnectinganorganorotherpart
tothebody)projectposteriorlyfromthevertebralbodyto
unitewiththeflatlaminatoformthevertebralarch.

26. •Togetherwiththebodyitformsvertebral
(spinal)foramenforthepassageofspinal
cordandconnectivetissue.
•Thepediclesexhibitsuperiorandinferior
indentationscalledvertebralnotches.
•Whenthevertebralnotchesarestackedon
topofoneanother,theyformanopening
betweenadjoiningvertebraeonbothsidesof
thecolumn.
•Eachopening,calledanintervertebral
foramen,permitsthepassageofasingle
spinalnervethatpassestoaspecificregion
ofthebody.

27. 3.Processes:Sevenprocessesarisefrom
thevertebralarch:
apairoftransverseprocessesatthepoints
wherelaminaeandpediclesjoin,
asinglespinousprocessposteriorlyfromthe
junctionofthelaminae;
andtwosuperiorandtwoinferiorarticular
processeswhichprovidearticulating
surfaces(facets)withthesuperiorand
inferiorvertebraerespectively.

28. Bones of the thorax
•Theskeletalpartofthethorax(chest),thethoraciccage,consistsofsternum,costal
cartilages,ribsandthebodiesofthethoracicvertebrae.
•Thethoraciccageisnarroweratthesuperiorendandbroaderatitsinferiorend
andisflattenedfromfronttoback.
•Functions:Itenclosesandprotectstheorgansinthethoracicandsuperior
abdominalcavities.
•Itprovidessupportforthebonesoftheshoulder(pectoral)girdleandupperlimbs.
•1Sternum:Thesternum(breastbone,about15cmlong)isaflat,narrowbone
locatedinthecenteroftheanteriorthoracicwallandconsistsof3parts:
•themanubrium(handlelikesuperiorpart),
•thebody(themiddleandlargestpart),and
•thexiphoidprocess(swordshapedinferior,smallestpart).

30. 2.Ribs:
•Twelvepairsofribsgivestructuralsupporttothesidesofthoraciccavity.
•Theyincreaseinlengthfrom1to7,andthendecreaseinlengthfrom8to12.
•Eachribarticulatesposteriorlywiththecorrespondingthoracicvertebra.
•Thefirst1-7pairsofribshaveadirectanteriorattachmenttothesternumbyastripof
hyalinecartilage(costalcartilage),providingelasticitytothethoraciccage.
•Theseribsarecalledtrue(vertebrosternal)ribsformingsternocostaljointswiththe
sternum.
•Theremaining5pairs(8-12)arecalledfalseribs(eitherattachindirectlytothesternumor
donotattachtosternum).
•Thecartilagesof8-10pairsofribsattachtooneanotherandthentothecartilagesof7th
pairofribs;thesearecalledvertebrochondralribs.

31. •The11thand12thpairsarecalledfloating(vertebral)ribsanddonotattachtothe
sternumatall.
•Costochondritis(inflammationofoneormorecostalcartilages)causeslocal
inflammationandpainandmimicsthechestpainassociatedwithaheartattack
(anginapectoris).
•Theposteriorportionoftheribconnectstoathoracicvertebrabyitshead
(vertebrocostaljoint)andthearticularpartofatubercle(abonyeminenceonthe
temporalboneintheskull).
•Intercostalspaces(betweenribs)areoccupiedbyintercostalmuscles,bloodvessels,
andnerves.
•Thecostalcartilagesaresufficientlyelasticinyoungerindividualstopermit
considerablebendingwithoutbreaking.
•Specialribrefractorsareusedtocreateawideseparationbetweenribstogain
accessforsurgeryoflungsorotherstructures.

32. Appendicular skeleton
•Theappendicularskeletonconsistsofthepectoralgirdle
withtheupperlimbsandthepelvicgirdlewiththe
lowerlimbs.
•1Pectoral(ShoulderGirdle):Thehumanbodyhastwo
pectoralgirdlesthatattachthebonesoftheupperlimbs
totheaxialskeleton.
•Thepectoralgirdlesconsistsof:1Clavicleand1Scapula
a.Clavicle(CollarBone):Itis'S'shapedlongbonewhich
hasadoublecurve.
•Themedialendisroundedandarticulateswiththe
manubriumofthesternumtoformthesternoclavicular
joint.

33. •Thebroad,fat,lateralendtheacromialend,articulates
withtheacromionofthescapulaformthe
acromioclavicularjoint.
•Theclavicleprovidesthebonylinkbetweentheupperlimb
andtheaxialskeleton.
b.Scapula:Itisalarge,flat,triangularshapedbone,lyingon
theposteriorchestwallsuperficialtotheribs.
•Atthelateralanglethereisathinarticularsurfacecalledas
glenoidcavityinwhichtheheadofthehumerusfitsand
formstheshoulderjoint.
•Ontheposteriorsurfacethereisaspinousprocesscalled
asacromionprocess.
•Acromionprocessarticulateswiththeclavicleatthe
acromioclavicularjoint.
•Thecoracoidprocess,aprojectionfromtheupperborder
ofthebone,givesattachmenttomusclesthatmovethe
shoulderjoint.

34. •2 Upper Limbs (Upper Extremity): Each upper limb has 30
bones in three locations.
•It consists of:
•The 1 Humerusin the arm
•The 1 Ulna and 1 Radius in the forearm
•The 8 Carpals in the carpus (wrist)
•The 5 Metacarpals in the metacarpus (palm)
•The 14 Phalanges (bones of the digits) in the hand
•Humerus:Itisthelongestandlargestboneoftheupper
limb.
•Itarticulatesproximallywiththescapulaanddistallytothe
elbowwithtwobonestheulnaandtheradius.
•Theproximalendofthehumerushasroundedheadthat
articulateswiththeglenoidcavityofthescapula.
•Neckispresentdistaltotheheadofhumerus.
•Thegreatertubercleisalateralprojectionpresentdistalto
theneck.

35. •Thelessertubercleprojectsanteriorly.
•Betweenthetwotuberclesthereisagroovecalledasintertubercularsulcus.
•Theshaftofthehumerusisroughlycylindricalatitsproximalend,butit
becomesflattenedandbroadatitsdistalend.
•Atthemiddleoftheshaft,thereisaroughenedV-shapedareacalledas
deltoidtuberosity.
•Thecapitulumisaroundedknobthatarticulateswiththeheadoftheradius.
•Thetrochlealocatedmedialtothecapitulumarticulateswiththeulna.
•Themedialepicondyleandlateralepicondyleareroughprojectionspresent
oneithersideofdistalendofthehumerus.

36. •Ulna:Ulnaandradiusarethetwobonesof
theforearm.
•Theulnaisrelativelylongerthantheradius.
•Attheproximalendoftheulna,olecranon
processispresent.
•Thetrochlearnotchisalargecurvedarea
betweentheolecranonandcoronoidprocess.
•Theradialnotchisapointthatarticulates
withtheheadoftheradius.
•Thedistalendoftheulnaconsistsofahead.
•Atthedistalendofulnastyloidprocessis
present.

37. •Radius:Theradiusisthesmallerboneoftheforearmandis
locatedonthelateralsideoftheforearm.
•Theradiusisnarrowatitsproximalendandwidensatits
distalend.
•Theproximalendoftheradiushasadisc-shapedheadthat
articulateswiththecapitulumofthehumerusattheelbow
joint.
•Theulnaandradiusarticulatedirectlyattheirproximaland
distalends.
•Theproximalendoftheradiusarticulateswiththeradial
notchoftheulnawhichiscalledasproximalradioulnar
joint.
•Aroughareaoftheneckiscalledasradialtuberosity.
•Theshaftoftheradiustothedistalendformastyloid
process.
•Abroadandfibrousconnectivetissuecalledas
interosseousmembranejoinstheshaftsofradiusandulna.

38. •Thedistalendoftheradiusarticulateswiththree
bonesofthewrist(thelunate,thescaphoid,and
thetriquetrum)toformtheradiocarpaljoint.
•TheCarpels(Wrist):Itistheproximalregionof
thehand.Itconsistsofeightsmallbones
arrangedintwotransverserowsconsistingof
fourboneseach.
•Itconsistsof:
•Proximalrow:Scaphoid,lunate,triquetrum,pisiform.
•Distalrow:Trapezium,trapezoid,capitate,hamate.
•Thebonesoftheproximalrowareassociated
withthewristjoint.
•Thebonesofthedistalrowformjointswiththe
metacarpalbones.

39. •TheMetacarpus(Palm):Itistheintermediateregionof
thehand.Itconsistsoffivebonescalledmetacarpals.
•Itconsistsof:
•Proximalbase
•Intermediateshaft
•Distalhead
•Themetacarpalbonesarenumberedas1-5,starting
withthethumb.
•Thebasesarticulatewiththedistalrowofcarpalbones
toformthecarpometacarpaljoints.
•Theheadsarticulatewiththeproximalphalangesto
formthemetacarpophalangealjoints.
•Phalanges(FingerBones):Itmakesupthedistalpartof
thehand.
•Thereare14phalangesinthefivedigitsofeachhand.

40. •Asingleboneofadigitiscalledasaphalanx.
•Eachphalanxconsistsof:
•Proximalbase
•Intermediateshaft
•Distalhead
•Thethumbhastwophalangesandotherfourdigits
havethreephalanges.
•Thefirstrowofphalanges(proximalrow)articulates
withthemetacarpalbonesandsecondrowof
phalanges.
•Thesecondrowofphalanges(middlerow)articulates
withtheproximalrowandthethirdrowcalledasdistal
row.
•Jointsbetweenphalangesarecalledinterphalangeal
joints.

41. •Pelvic(Hip)Girdle:Itconsistsoftwohipbones
calledaspelvicbones.
•Thehipbonesunitetogethertoformthepubic
symphysis.
•Thehipbonesunitetogetherposteriorlywith
thesacrumatthesacroiliacjoints.
•Thecompleteringcomposedofthehipbones,
pubicsymphysis,andsacrumformsadeep,
basinlikestructurecalledasthebonypelvis.
•Thebonypelvisprovidesastrongsupportfor
thevertebralcolumn,pelvicandlower
abdominalorgans.

42. •Ahipboneconsistsofthreebones:
•Ilium✓
•Pubis
•Ischium
•Ilium:
•Itisthelargesthipbone.
•Itiscomposedofasuperiorwingandaninferior
body.
•Thebodyhelpstoformtheacetabulum,the
socketfortheheadoffemur.
•Thesuperiorborderofiliumiscalledastheiliac
crest.
•Theiliaccrestendsspinethatserveaspointsof
attachmentforthemusclesofthetrunk,hip,and
thighs

43. •Ischium:Itistheposteriorportionofthehipbone.
•Itiscomposedofasuperiorbodyandaninferiorramus.
•Theramusistheportionofischiumthatfuseswiththepubis.
•Togethertheramusandthepubissurroundtheobturatorforamen,the
largestforamenintheskeleton.
•Pubic:Itistheinferiorpartofhipbone.
•Theacetabulumisadeepfossaformedbytheilium,ischiumandpubis.
•Itfunctionsasthesocketthatacceptstheroundedheadofthefemur.

44. •4 Lower Limb (Lower Extremity):
•Each lower limb consists of 30 bones in four
locations.
•They consists of:
•Femur in the thigh
•Patella (knee cap)
•Tibia and fibula in the leg
•7 tarsals in the tarsus (ankle)
•5 metatarsals in the metatarsus
•14 phalanges (bones of the digits) in the foot

45. •Femur(ThighBone):Itisthelongest,heaviestand
strongestboneofthebody.
•Itsdistalendarticulateswiththetibiaandpatella.
•Theproximalendconsistsofaroundedheadthat
articulateswiththeacetabulumofthehipboneto
formthehipjoint.
•Theneckisaconstrictedportionpresentdistaltothe
head.
•Thedistalendofthefemurconsistsofmedialcondyle
andlateralcondyle.
•Thesearticulatewiththemedialandlateralcondyles
ofthetibia.
•Adepressedareabetweenthecondylesonthe
posteriorsurfaceiscalledtheintercondylarfossa.

46. •Patella(KneeCap):Itisasmall,
triangularbonelocatedanteriortothe
kneejoint.
•Itconsistsoftwoparts:
•Base:Itisbroadproximalendofpatella.
•Apex:Itispointeddistalend.
•Theposteriorsurfacecontainstwo
articularsurfaces,
•oneformedialcondyleofthefemurand
•anotherforlateralcondyleofthefemur.

47. •Tibia:Tibiaorshinboneisthelargerandweight
bearingboneoftheleg.
•Itarticulatesatitsproximalendwiththefemur
andfibula,andatitsdistalendwiththefibulaand
thetalusboneoftheankle.
•Theproximalendoftibiaisexpandedintolateral
condyleandmedialcondyle.Thesearticulatewith
thecondylesofthefemur.
•Thetibiaatitsanteriorsurfaceconsistsoftibial
tuberosity.
•Thedistalendoftibiaformsthemedialmalleolus.
•Medialmalleolusarticulateswiththetalusofthe
ankle.

48. •Fibula:Thefibulaisparallelandlateraltothetibia,butitissmaller.
•Theproximalheadofthefibulaarticulateswiththelateralcondyleofthe
tibiatoformtheproximaltibiofibularjoint.
•Thedistalendisarrowheadshapedandconsistsofaprojectioncalledas
lateralmalleolusthatarticulateswiththetalusoftheankle.
•Thetibiaandfibulaareconnectedbyaninterosseousmembrane.
•Thefibulaarticulateswiththetibiaatthefibularnotchtoformthedistal
tibiofibularjoint.

49. •Tarsals, Metatarsals and
Phalanges:
•Tarsals(Ankle):Itistheproximalregionof
thefoot.Itconsistsofseventarsalbones.
•Theyconsistoftalusandcalcaneuslocatedin
theposteriorpartofthefoot.
•Thetalusisthemostsuperiortarsalbone.
•Thecalcaneusisthelargestandstrongest
tarsalbone.
•Theanteriortarsalbonesarethenavicular,
threecuneiformbones,andthecuboid.

50. •Jointsbetweentarsalbonesarecalledasintertarsaljoints.
•Metatarsus:Itistheintermediateregionofthefoot,consistsoffive
metatarsalbonesnumbered1-5fromthemedialtolateralposition.
•Eachmetatarsalconsistsof:
•Proximalbase
•Intermediateshaft
•Distalhead
•Themetatarsalsarticulateproximallywiththefirst,second,andthird
cuneiformboneandwiththecuboidtoformthetarsometatarsaljoints.
•Distallytheyarticulatewiththeproximalrowofphalangestoform
metatarsophalangealjoints.

51. •Phalanges:Itisthedistalcomponentofthefoot.
•Thephalangesarenumberedfrom1-5beginningwiththegreattoe,frommedial
tolateral.
•Eachphalanxconsistsof:
•Proximalbase
•Intermediateshaft
•Distalhead
•Thetoehastwolargephalangescalledproximalanddistalphalanges.
•Theotherfourtoesconsistofthreephalangesproximal,middleanddistal.
•Jointsbetweenphalangesofthefootarecalledinterphalangealjoints.

52. Organization of skeletal muscle
•1SkeletalMuscleTissue.Skeletal
musclesaremadeupofhundredsto
thousandsofcellswhicharecalledas
musclefibres.
•Themusclefibresareofelongated
shapes.
•Theoutermostlayerencirclingthe
entiremusclecalledasepimysium.
•Perimysiumsurroundsagroupof10to
100ormoremusclefibresseparating
themintobundlescalledasfascicles.
•Endomysiumisasheathofareolar
connectivetissuethatpenetratesthe
interiorofeachfascicleandseparates
individualmusclefibresfromone
another.

53. •Theepimysium,perimysiumandendomysiumbindsthefibresintohighlyorganized
structureandblendstogetherattheendofmusclestoformtendonswhicharerope
shapedbutsometimesittakessheetlikestructurecalledasaponeurosis.
•Thetendonattachesthemuscletobones.
•SkeletalMuscleFibre:Itisroughlycylindricalinshape.
•Theylieparalleltooneanotherwithalternatedarkandlightstrips.
•Individualfibremaybeverylong,upto25cminthelongestmuscle.
•Eachcellhasseveralnucleiwhicharesituatedjustunderthecellmembranecalled
assarcolemma.
•Thecytoplasmofmusclecellsiscalledassarcoplasm.
•Skeletalmusclefibrescontainmanymitochondriawhichareusedforproductionof
ATPfromglucoseandoxygen.

54. •Sarcoplasmalsocontainsredcoloured,oxygen
bindingproteincalledasmyoglobinwhich
storesoxygenwithinthemolecule.
•MyofibrilsandSarcoplasmicReticulum:At
highermagnification,thesarcoplasmappears
stuffedwithlittlethreads.
•Thesesmallstructuresarecalledasmyofibrils.
•Myofibrilsareabout2µmindiameter.
•Afluid-filledsystemofmembranoussacscalled
assarcoplasmicreticulum(SR),encircleseach
myofibrils.
•Inrelaxedmusclefibre,theSRstorescalcium
ions.
•Releaseofcalciumfromtheterminalcisternsof
theSRtriggersmusclecontraction.

55. •FilamentsandSarcomere:Withinmyofibrilsaresmallerstructurecalledasfilaments.
•Twotypesoffilamentsarepresent:
•Thinfilament
•Thickfilament
•Thinfilamentsare8mmindiameterand1-2µmlong.
•Thickfilamentsare16mmindiameterand1-2μmlong.
•Boththesethinandthickfilamentsareinvolvedincontraction.
•Thefilamentsinthemyofibrilsdonotextendtheentirelengthofamusclefibre.

56. •Insteadtheyarearrangedincompartmentscalledas
sarcomere,thebasicfunctionaluniteofmyofibrils.
•Z-discsseparateonesarcomerefromthenext.
•Sarcomereistherepeatingcontractileunitsofmyofibril.
•Itisasegmentconsistingofahighlyorganizedassemblyof
filamentssurroundedbytwoZlines.
•Twoimportantproteinsnamelyactinandmyosinformthin
andthickfilamentsrespectively.
•Thefilamentspartlyoverlapandslidepasteachotherduring
contraction.
•VerticalproteinplatescalledZdiscsformthesideboundaries
ofasarcomere.
•Duringcontraction,thethickfilamentspullthethinfilaments
towardsthecenterofthesarcomeres.
•Thismovementcausesthesarcomere,myofibrilsandthe
musclefibrestoshorten.

57. •Muscleprotein:Myofibrilsaremadeupofthreetypesofproteins.
1.Contractileprotein:Ithelpsincontractionprocess.
2.Regulatoryprotein:Itregulatesthecontractionprocessbyswitchingonorshuttingthe
process.
3.Structuralprotein:Itkeepsthickandthinfilamentsinproperalignmentandresponsiblefor
myofibrilelasticityandextensibility.
•Thickfilamentsaremadeupofproteincalledasmyosin.
•Thinfilamentsaremadeupofproteincalledasactin.
•Smalleramountoftworegulatoryproteins,tropomyosinandtroponinarealso
partofthinfilament.

58. Physiology of muscle contraction
•SlidingFilamentMechanismofMuscleContraction:
•Thelengthofskeletalmuscleshortensduringcontractionbecausethethickandthinfilamentsslide
overoneanother.
•Theprocessisknownastheslidingfilamentmechanism.
•Thethickfilamentscontain300myosinmolecules.
•Itconsistsoftwoparts:
•Myosintail
•Myosinheads
•Myosintailformstheshaft(tube)ofthethickfilamentandheadsprojecttowardsthethinfilament.
•Thinfilamentscontainactin,troponinandtropomyosin.Attheonsetofcontraction,thesarcoplasmic
reticulumreleasescalciumions(Ca+2)intothecytosol.
•There,theybindtotroponinandcausethetroponin-tropomyosincomplexestomoveawayfrom
myosinbindingsiteonactin

59. •Oncethebindingsitesarefree,therepeatingsequenceofeventsofthe
contractioncycleoccursthatcausesthefilamentstoslideoneachother.
•Thecontractioncycleconsistsoffoursteps:
1.ATPHydrolysis:ThemyosinheadincludesanATP-bindingsiteandanATPase,an
enzymethathydrolysesATPintoADP(adenosinediphosphate)andaphosphate
group.
•Thishydrolysisgivesenergytomyosinhead.
•ADPandaphosphategroupremainattachedtothemyosinhead.
2.Attachmentofmyosintoactintoformcross-bridges:Theenergizedmyosinhead
attachestothemyosinbindingsiteonactinandreleasesthepreviouslyhydrolysed
phosphategroup.

60. Whenthemyosinheadsattachtoactinduringcontraction,theyarereferredtoas
crossbridges.
3.Powerstroke:Oncethecross-bridgesareformed,thepowerstrokeoccurs.
•Thecross-bridgerotatestowardsthecentreofthesarcomereandreleasesthe
ADPmolecule.
•Thecross-bridgegeneratesaforcewhichslidesthethinfilamentoverthethick
filament.
4.Detachmentofmyosinfromactin:Attheendofthepowerstroke,thecross-
bridgeremainsfirmlyattachedtoactinuntilitbindsanothermoleculeofATP.
AsATPbindstotheATPbindingsiteonthemyosinhead,themyosinheaddetaches
fromactin

62. Neuromuscular Junction (NMJ)
•Theneuronsthatstimulatetheskeletalmuscle
fibrestocontractarecalledsomaticmotor
neurons.
•Neuromuscularjunctionisthesynapsebetweena
somaticmotorneuronandaskeletalmusclefibre.
•Asynapseisaregionbetweentwoneurons,or
betweenaneuronandatargetcells(between
somaticmotorneuronandmusclefibre).
•Synapsecontainsasmallgap,calledassynaptic
cleftwhichseparatesthetwocells.
•Thefirstcellcommunicateswiththesecondcellby
releasingachemicalcalledasneurotransmitter.
•AttheNMJ,theendofthemotorneuroncalledas
axonterminal,dividesintoaclusterofsynaptic
endbulbs.

63. •Inthecytosolwithineachsynapticendbulbcontainshundredsofmembrane
enclosedsacscalledsynapticvesicles.
•Insideeachsynapticvesiclearethousandsofmoleculesofacetylcholine(Ach),
theneurotransmitter,releasedattheNMJ.
•Theregionofthesarcolemmaoppositethesynapticendbulbs,calledthe
motorendplateisthemusclefibrepartoftheNMJ.
•Withineachmotorendplateare30to40millionacetylcholinereceptorsare
presentandprovidesalargesurfaceareaforAchbinding.
•Aneuromuscularjunctionincludesallthesynapticendbulbsononesideof
thesynapticcleft,plusthemotorendplateofthemusclefibreontheother
side.