Y khoa, y dược - Bones and skeletal tissues: Part A

6 Bones and Skeletal Tissues: Part ASkeletal CartilagesContain no blood vessels or nervesDense connective tissue girdle of perichondrium contains blood vessels for nutrient delivery to cartilageSkeletal CartilagesHyaline cartilagesProvide support, flexibility, and resilienceMost abundant typeElastic cartilagesSimilar to hyaline cartilages, but contain elastic fibersFibrocartilagesCollagen fibers—have great tensile strengthFigure 6.1Axial skeletonAppendicular skeletonHyaline cartilagesElastic cartilagesFibrocartilagesCartilagesBones of skeletonEpiglottisLarynxTracheaCricoidcartilageLungRespiratory tube cartilagesin neck and thoraxThyroidcartilageCartilage inexternal earCartilages innoseArticularCartilageof a jointCostalcartilageCartilage inIntervertebraldiscPubicsymphysisArticular cartilageof a jointMeniscus (padlikecartilage inknee joint)Growth of CartilageAppositionalCells secrete matrix against the external face of existing cartilageInterstitialChondrocytes divide and secrete new matrix, expanding cartilage from withinCalcification of cartilage occurs duringNormal bone growthOld ageBones of the SkeletonTwo main groups, by locationAxial skeleton (brown)Appendicular skeleton (yellow)Figure 6.1Cartilage inexternal earCartilages innoseArticularCartilageof a jointCostalcartilageCartilage inIntervertebraldiscPubicsymphysisArticular cartilageof a jointMeniscus (padlikecartilage inknee joint)Classification of Bones by ShapeLong bonesLonger than they are wide Short bonesCube-shaped bones (in wrist and ankle)Sesamoid bones (within tendons, e.g., patella)Classification of Bones by ShapeFlat bonesThin, flat, slightly curved Irregular bonesComplicated shapes Figure 6.2Functions of BonesSupportFor the body and soft organsProtectionFor brain, spinal cord, and vital organsMovementLevers for muscle actionFunctions of BonesStorageMinerals (calcium and phosphorus) and growth factorsBlood cell formation (hematopoiesis) in marrow cavities Triglyceride (energy) storage in bone cavitiesBone MarkingsBulges, depressions, and holes serve asSites of attachment for muscles, ligaments, and tendonsJoint surfacesConduits for blood vessels and nervesBone Markings: ProjectionsSites of muscle and ligament attachmentTuberosity—rounded projectionCrest—narrow, prominent ridge Trochanter—large, blunt, irregular surfaceLine—narrow ridge of boneTubercle—small rounded projectionEpicondyle—raised area above a condyleSpine—sharp, slender projectionProcess—any bony prominenceTable 6.1Bone Markings: ProjectionsProjections that help to form jointsHeadBony expansion carried on a narrow neckFacetSmooth, nearly flat articular surfaceCondyleRounded articular projectionRamusArmlike bar Table 6.1Bone Markings: Depressions and OpeningsMeatusCanal-like passagewaySinusCavity within a boneFossaShallow, basinlike depressionGrooveFurrowFissureNarrow, slitlike openingForamenRound or oval opening through a boneTable 6.1Bone TexturesCompact boneDense outer layerSpongy (cancellous) boneHoneycomb of trabeculae Structure of a Long BoneDiaphysis (shaft)Compact bone collar surrounds medullary (marrow) cavityMedullary cavity in adults contains fat (yellow marrow)Structure of a Long BoneEpiphysesExpanded ends Spongy bone interior Epiphyseal line (remnant of growth plate) Articular (hyaline) cartilage on joint surfaces Figure 6.3a-bProximalepiphysis(b)(a)EpiphyseallineArticularcartilagePeriosteumSpongy boneCompact boneMedullarycavity (linedby endosteum)Compact boneDiaphysisDistalepiphysisMembranes of BonePeriosteumOuter fibrous layerInner osteogenic layerOsteoblasts (bone-forming cells)Osteoclasts (bone-destroying cells)Osteogenic cells (stem cells)Nerve fibers, nutrient blood vessels, and lymphatic vessels enter the bone via nutrient foraminaSecured to underlying bone by Sharpey’s fibersMembranes of BoneEndosteumDelicate membrane on internal surfaces of boneAlso contains osteoblasts and osteoclastsFigure 6.3c(c)Yellowbone marrowEndosteumCompact bonePeriosteumPerforating(Sharpey’s) fibersNutrientarteriesStructure of Short, Irregular, and Flat BonesPeriosteum-covered compact bone on the outside Endosteum-covered spongy bone within Spongy bone called diploë in flat bones Bone marrow between the trabeculaeFigure 6.5Compactbone TrabeculaeSpongy bone(diploë)Location of Hematopoietic Tissue (Red Marrow)Red marrow cavities of adultsTrabecular cavities of the heads of the femur and humerusTrabecular cavities of the diploë of flat bonesRed marrow of newborn infantsMedullary cavities and all spaces in spongy bone Microscopic Anatomy of BoneCells of bonesOsteogenic (osteoprogenitor) cellsStem cells in periosteum and endosteum that give rise to osteoblastsOsteoblastsBone-forming cellsFigure 6.4a-b(a) Osteogenic cell(b) OsteoblastStem cellMatrix-synthesizingcell responsiblefor bone growthMicroscopic Anatomy of BoneCells of boneOsteocytesMature bone cellsOsteoclastsCells that break down (resorb) bone matrix Figure 6.4c-d(c) OsteocyteMature bone cellthat maintains thebone matrix(d) OsteoclastBone-resorbing cellMicroscopic Anatomy of Bone: Compact BoneHaversian system, or osteon—structural unitLamellaeWeight-bearingColumn-like matrix tubesCentral (Haversian) canalContains blood vessels and nervesFigure 6.6Structuresin thecentralcanalArtery withcapillariesVeinNerve fiberLamellaeCollagenfibersrun indifferentdirectionsTwistingforceMicroscopic Anatomy of Bone: Compact BonePerforating (Volkmann’s) canalsAt right angles to the central canalConnects blood vessels and nerves of the periosteum and central canalLacunae—small cavities that contain osteocytesCanaliculi—hairlike canals that connect lacunae to each other and the central canalFigure 6.7a-cEndosteum lining bony canalsand covering trabeculaePerforating (Volkmann’s) canalPerforating (Sharpey’s) fibersPeriosteal blood vesselPeriosteumLacuna (withosteocyte) (a)(b)(c)LacunaeLamellaeNerveVeinArteryCanaliculiOsteocytein a lacunaCircumferentiallamellaeOsteon(Haversian system)Central(Haversian) canalCentralcanalInterstitial lamellaeLamellaeCompactbone Spongy boneMicroscopic Anatomy of Bone: Spongy BoneTrabeculaeAlign along lines of stressNo osteonsContain irregularly arranged lamellae, osteocytes, and canaliculiCapillaries in endosteum supply nutrientsFigure 6.3b(b)LacunaeLamellaeNerveVeinArteryCanaliculusOsteocytein a lacunaCentralcanalChemical Composition of Bone: OrganicOsteogenic cells, osteoblasts, osteocytes, osteoclastsOsteoid—organic bone matrix secreted by osteoblastsGround substance (proteoglycans, glycoproteins)Collagen fibersProvide tensile strength and flexibilityChemical Composition of Bone: InorganicHydroxyapatites (mineral salts)65% of bone by massMainly calcium phosphate crystalsResponsible for hardness and resistance to compression