ChapterlOsteology·9.compactbone.ticular surfaces.The depressions or tunnels are alwaysCertain irregular bones contain air-filled spaces orlodged or penetrated by blood vessels and nerves.sinuses lined by epithelium and are known as pneu-Important markings are summarized as the elevations,maticbones,forexample,theethmoid and maxillae.expanded ends for articulation, small flat area for ar-Theymake the skull light in weight, help in resonanceticulation,depressions, cavities and openings.of voice,and actas airconditioning chambersfortheA linear elevation is referred to as a line, ridgeinspiredair.or crest; a rounded elevation as a tubercle (small),Inaddition,therearesomesesamoid bonesinourtuberosity (large)，protuberance, trochanter or malle-body.Thesesamoidbonesarebonynodules foundolus; and a sharp elevation as a spine,spinous processembedded in the tendons or joint capsules.They haveor styloid process.The expanded end for articulationnoperiosteumand ossifyafterbirth.Theyarerelatedis named as ahead, condyle or epicondyle:and theto an articular or nonarticular bony surface,and thesmall flat area for articulation as a facet.Depressionssurfaces of contact are covered with hyaline cartilageare of variable shape and are described as the fossa,and lubricated byabursaor synovial membrane.Ex-depression, notch, groove or sulcus, etc. A cavityamples includethe patella,pisiformbone,etc.Func-within the bone mayberegarded as a sinus or an an-tions of thesesamoidbones aretoresistpressure,trum.A short perforation is called a foramen or fissureminimise friction,alter the direction of pull of theoraperture;and alonger passageisa canal orduct,ormuscle, and to maintain the local circulation.ameatus.I.Markings of BonesII.Structure of BonesWhen the surface of a bone is examined certainA living bone consists of the bony substance,elevations and depressions,known asbonemarkings,periosteum and endosteum,and bonemarrow, and isare seen. The elevations or projections are generallyabundant in blood and nerve supply (Fig.I-1-3)attached by tendons or ligaments, and are near the ar.ArticularcartilageArticularcapsuleSpongybonePeriosteumCompactboneTrabeculaeShortboneMarrowcavityLaminaPeriosteumextemaDiploeLaminainternaFlat boneLongbonenarrowFig.I-1-3Structure ofbones-扫描全能王创建
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the articular surfaces.The abundant periosteal blood.10.PARTILOCOMOTORSYSTEMvessels nourish the outer part of the underlying bonealso, so a bone from which the periosteum has been1.Bony substanceremoved will die. Periosteum has a rich nerve sup.ply which makes it the most sensitive part of a bone,Bony substance includes the compact bone andthat is why pain from the broken bone is severe.Thespongy or cancellous bone. The compact bone isperiosteum is made up of an outer or fibrous layer,dense in texture like ivory, but is extremely porous.and an inner or cellular layer. The outer layer is denseIt is an adaptation to bending and twisting forces (aand unites the periosteum to the underlying bonecombination of compression,tension and shear).Theby fibres. At the articular margin the periosteum iscompact bone forms the shaft of long bone, the ex-continuous with the capsule of joint. The inner layerternal layer of epiphyses and of other kinds of bones.In addition, it forms the outer and inner plates of thecontains osteoblasts and osteoclasts, which plays anflat cranial bones. In a light micrograph (Fig.I -1-4)important role in regeneration of the bone.The func-the basic functional unit of mature compact bone istion is most active during the period of development,the cylindrical osteon or Haversian system. Within angrowth, reconstruction and repairing of bones.Forosteon the osteocytes are arranged in concentric lay-the purpose of prevention of bony necrosis or delayeders around a central canal, or Haversian canal, whichhealing,itis necessaryto preserveperiosteum ascontains blood vessels supplying the osteon. Centralmuch as possible during operation.canal usually run parallel to the surface of bone.The membrane lying the inner surfaces of medullary cavity and of spaces within spongy bone isCentral canalsknown as the endosteum, which contains osteoblastsand osteoclasts also.Canaliculi3.Bone marrowConcentriclamellaeBone marrow is found in the medullary cavitiesof long bones and in spaces between the trabeculaewithin cancellous bones.There are twokinds of boneOsteonmarrow, the red and yellow. The red bone marrowLacunaeperformsthefiunction ofhemopoeisis (blood-forming)andconsists of many hemopoietic stem cells and devel-oping blood cells of varied periods; while the yellowbone marrow comprises a lot of fat, with no power ofFig.I-1-4 Light micrograph of osteonshaemopoiesis.The spongy or cancellous bone consists of a lot ofAt birth the marrow is red everywhere with wide-trabeculae which interweave witheach other to formspread active haemopoiesis. As the age advances, thea meshwork like a honeycomb.The trabeculae run inred marrow at many places atrophies and is replaceddirections suited to their function, and are arrangedby yellow, fatty marrow. By the sixth year, the redin line of the pressure and of the tension.The cancel-marrow in medullary cavities is gradually replaced bylous boneis anadaptationto compressiveforces.Itisthe yellow marrow. At about 18th year, the red mar-distributed in the interiorof epiphyses and of all otherrow is almost entirely replaced by the yellow one inbones of limbs. Red marrow persists in the cancellouskinds of bones.The spongy bone in the flat cranialbones isknown as the diploe.ends of long bones. In the axial bones, e.g. skull, ver-tebrae, sternum and ribs, and in the iliac crest the redmarrow is found throughout life. It is a useful method.Periosteum and endosteumto make a diagnosis of some blood diseases to do apuncture on the iliac crest (or on the spinous processPeriosteum is a membrane of fibrous connectiveofa lumbar vertebra, or on the stemum) to examinetissue, investing the whole of the bone except forthemarrowInsometypesofanemia, thedeathrate口扫描全能王创建O
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ChapterlOsteology.11.ofred ells ishigh, and thyellowmarrowmayrvetothered in anendeavor tosupport thebirthrate.V . Vasculature and Inner-vationof BonesIV.Chemical Compositionand Physical Properties ofBones are furnished with an abundance of bloodvessels.In a long bone, there arethree major sets ofBonesblood supply (Fig.I-1-5).①The nutrient arteries,accompanied by veins, enter the medullary cavityThe bone matrix is made up of organic and inor-through the nutrient foramina to supply the boneganic components. The organic components consistmarrow. As they penetrate the shaft, their branchespredominantly of collagen and proteoglycans, andextend along the central canal and supply the osteonsaccount for roughly one-third of the weight of theof compact bone. ②The metaphyseal vessels arebone. Collagen fibers give the bones resilience andthe second set of blood supply.These vessels providetoughness. They can tolerate stretching, twisting andblood to the epiphyseal plate, where the cartilage isbending,but when exposedto compression,theybendreplacedbythebone.③Theperiostealarteriesfromoutof the way easily.The collagen fibers also providethe periosteum, in company with veins, are the thirdan organic framework for the formation of mineralset of blood supply.They enter the shaft at numerouscrystal. Proteoglycans can organize collagen fibrespoints to supplythe superficial compactbone.Alland bind growth factors,which is important to thethree sets of vessels anastomosewitheach other ex-bonegrowth.tensively.The inorganic components or mineral salts andmainly thecalcium phosphateor Ca,(PO)2,whichArticularform almost two-thirds weight of the bone.The calci-cartilageBranchofumphosphateis deposited amongtheorganic frame-nutrient arterywork and interactswith calciumhydroxidetoformMetaphysealPeriosteumarterycrystals of hydroxyapatite.Calcium phosphate crystals give the bones hardness and rigidity.They canwithstand compression, but the crystals are likely toPeriostea-Periosteumshater whenexposedtotwisting,bending,or suddenarteriesimpacts.CompactbonePhysical properties of bones depend upon the bal-Connectionstosuperficial osteonsance between the organic and inorganic componentsNutrient artery-Marrowcavitywhich change with age. In infant or in child bones, or-ganic components are relatively more and the bones areNutrient foramensofer and not easy to be broken. Thus, a fracture in chil.dren are greenstick fractures (incomplete breaks causedby bending ofthebone)and heal fasterthan thoseinadultbons.Whieinthe bones inold ple,iogancomponents are comparatively more, and the bones areMetaphysealmore fragile and easer to be fractured.arteryAtest can be taken to demonstrate therelationshipEpiphysealbetween the chemical components and the physicalplateproperties of the bones. If we treat a bone with aFig.I-1-5 Blood supply of long bonemineral acid,wecanremovetheinorganicmatrixandleaveoganmatalSuchecimnixThe blood vessels of the short, flat and iregularandstildisplaysthe shapeoftheuntreated bone,forbones come from the periosteum. Large irregularexample,adealcifedribcan easily betied inaknot.bones like the hip bone also receive vessels from theIfaboneiscompletelybumtou,theorganicmatrinutrient arteries. The flat bones of the skull whichcan bermoved and the bone will b britle,cumblehave two layers of compact bone enclosing a layer ofand broken easily.cancellous bone (diploe) are supplied by numerous口扫描全能王创建可
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.12·PARTI LOCOMOTORSYSTEMlayeroftheeriosteumsoonproducesabonecollarvessels. In the diploe there are a lot of venous chan-thin layer ofbone around the shaftofcartilage model.nels known as the diploic veins. They communicateBlood vessels penetrate the cartilage and invade thewith both intracranial and extracranial veins, whichcenter region. Mesenchymal cells migrating with themay allow the spread of infections from outside oftheblood vessels differentiate into osteoblasts that beginskull to the bone itself and to intracranial structures.to producethe centerofossification,the primaryossi-These veins are also important during X-ray examina-fication center.Bone formation then spreads along thetion, because they are easily seen, especially in oldershaft.people,and may be confused with skullfractures.Bone remodeling occurs as the bone growth con-Veins runwith the arteries or leave thebone sep-tinues and a medullary or marrow cavity is created.arately. Lymphatic vessels are abundant in the perios-The shaft of the bone becomes thicker and thicker.teum.Nerves accompanythe blood vessels of bones,and the cartilage near the epiphysis is replaced by theand are distributed widelyto the periosteum (includingbone gradually.Thereby, the diameter and length ofthe endosteum),bony substance and bone marrow.the bone are increased.OfwhichthevasomotornervescontrolbloodvesselsAround the time of birth, the center of epiphysialwithin bones.cartilage begins to calcify.Capillaries and osteoblastsmigrate into the epiphysis, creating a secondary os-VI.Development of Bonessification center. The epiphysis is soon filled withspongy bone,and the thin cap of the original cartilageThe bones are derived from mesenchyme (em-model is remained and exposed to the joint cavity asbryonic cellular connectivetissue)bytwo differentthe articular cartilage.Then the secondary center ofpatterns,i.e.intramembranous ossification and endoossification grows toward the shaft until the shaft andchondral ossification.epiphyses are separated only by a thin plate of carti-lage, known as the epiphysial plate. Within the epiph-.Intramembranous ossificationysial plate, the chondrocytes continue to be dividedand enlarged, and the cartilage at the epiphysis side ofMesenchymal modelof bone is formed duringthethe epiphysial plate is gradually replaced by the bone.Overall, the thickness of the epiphyseal platedoesnotembryonic period and it begins to undergo the directossification in the fetal period. This type of bone de-change. On the shaft side of epiphyseal plate, osteo-blasts and capillaries continue to invade the cartilag-velopment is called the intramembranous ossification.inous lacunae and replace the dead of cartilage withthe livingbone.Endochondral ossification4It is obvious that the increase in the circumferenceof the bone is brought about by the deposition of newBy the time of 6 weeks old, the proximal bonesbone formed by the cells of the inner layer of peri-of limbs of an embryo, cither the humerus or femur,osteum; while the increase in the length of the bonehave been formed, but they are composed entirely oftakes place at the epiphysial cartilage, followed byhyaline cartilage.Then most of the hyaline cartilageossificationmodules are replaced by bones, and this kind of boneDuring the mature period, the rate of productiondevelopment is known as the endochondral ossificaofthe epiphyeal cartilage is slow down,and therattion, The formation of a long bone proceeds in theof osteoblast activity is accelerated.As a result, thefollowingmanners(Fig.l-1-6)epiphysial plate gets thinner and thinner, until it ul-Initially,the cartilage model isformed and then istimately disappears and becomes the epiphysial line.enlarged. Chondrocytes in the shaft of cartilage mod-This event is called the epiphysial closure, and nowel increase greatly in size,and the surrounding matrixthebonegrowth isstopped.Thecartilaginous epiphbegins to calcify. Due to the absence of nutrientsysial platecannotbeseenonradiographbecausethethese chondrocytes die and disintegrate. In the mean-cartlagedoes not aborbX-ray,but theepiphyialtime, the cells of perichodrium surrounding the shafline can be detected in X-rayfilmdifferentiate intoosteoblasts, and the perichodriumMost epiphyses inthe limbs begintoossify duringis converted into a periosteum.The inner osteogenicchiloowyarsaenghanD口扫描全能王创建合品
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Chapterl Osteology·13ULRboys. Most of the epiphyses become completely ossi-bone is finished entirely in the 25th year.fied during the 18th-20th years. The development ofEnlargingchondrocytes withinMarrowcalcifyingmatrixcavityEpiphysisPrimarycenterofossificationDiaphysisBonecollarBoneformatiorBloodSpongybyosteogenicbonevessellayerHyaline cartilageSpongyboneHyaline cartilageArticularcartilageEpiphysisMarrowcavityEpiphyseaplateMetaphysisPeriosteumDiaphysisCompactboneSecondaryossificationcenterFig.I-1-6 Endochondral ossificationprovide a framework for the attachment of soft tissueand organs.VII . Functions of BonesProtectionThe functions of bones can be summed below:The bones are connected by joints to form theSupportskeleton which protect important organs or viscera.The skull encloses the brain, the vertebrae shield theThebonysystemprovidesastructuralsupporforspinal cord, the ribs protect the heart and lungs, andu口口扫描全能王创建2
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