Chapter 6: Bones and Skeletal Tissues. Axial skeleton Appendicular skeleton Hyaline cartilages...

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Transcript of Chapter 6: Bones and Skeletal Tissues. Axial skeleton Appendicular skeleton Hyaline cartilages...

  • Chapter 6: Bones and Skeletal Tissues

  • Axial skeletonAppendicular skeletonHyaline cartilagesElastic cartilagesFibrocartilagesCartilagesBones of skeletonEpiglottisLarynxTracheaCricoidcartilageLungRespiratory tube cartilagesin neck and thoraxThyroidcartilageCartilage inexternal earCartilages innoseArticularCartilageof a jointCostalcartilageCartilage inIntervertebral discPubicsymphysisArticular cartilageof a jointMeniscus (padlikecartilage in knee joint)

  • Skeletal CartilagesContain no blood vessels or nervesDense connective tissue girdle of perichondrium contains blood vessels for nutrient delivery to cartilage3 types:Hyaline cartilagesProvide support, flexibility, and resilienceMost abundant typeElastic cartilagesSimilar to hyaline cartilages, but contain elastic fibersFibrocartilagesCollagen fibershave great tensile strength

  • 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 age

  • Bones of the SkeletonTwo main groups, by locationAxial skeleton: long axis of body: skull, vertebral column, rib cageAppendicular skeleton: upper and lower limbs that attach to axial skeleton

  • Types of bonesLong bones: longerthan wideShort bonesCube shaped bones (in wrist and ankle)Sesamoid bones (within tendons, e.g., patella)Flat bones: thin, flat, slightly curvedIrregular bones:complicated shapes

  • Functions of BonesSupport for the body and soft organsProtection for brain, spinal cord, and vital organsMovement: Levers for muscle actionStorage of minerals (calcium and phosphorus) Storage of growth factors (like insulin-like growth factor) in bone matrixBlood cell formation (hematopoiesis) in marrow cavities Triglyceride (energy) storage in bone cavities

  • Bone MarkingsBulges, depressions, and holes serve asSites of attachment for muscles, ligaments, and tendonsJoint surfacesConduits for blood vessels and nerves

  • Bone Markings: ProjectionsSites of muscle and ligament attachmentTuberosityrounded projectionCrestnarrow, prominent ridge Trochanterlarge, blunt, irregular surfaceLinenarrow ridge of boneTuberclesmall rounded projectionEpicondyleraised area above a condyleSpinesharp, slender projectionProcessany bony prominence

  • Bone MarkingsProjections that help to form jointsHead: bony expansion carried on a narrow neckFacet: Smooth, nearly flat articular surfaceCondyle: Rounded articular projectionRamus: Armlike bar

  • Bone Markings: Depressions and OpeningsMeatus: Canal-like passagewaySinus: Cavity within a boneFossa: Shallow, basinlike depressionNotch: indentation at the edge of a structureGroove: FurrowFissure: Narrow, slitlike openingForamen: Round or oval opening through a bone

  • Bone TexturesCompact boneDense outer layerSpongy (cancellous) boneHoneycomb of trabeculae Spongy boneCompact bone

  • Structure of a Long BoneDiaphysis (shaft)Compact bone collar surrounds medullary (marrow) cavityMedullary cavity in adults contains fat (yellow marrow) EpiphysesExpanded ends Spongy bone interior Epiphyseal line (remnant of growth plate) Articular (hyaline) cartilage on joint surfaces

  • ProximalepiphysisEpiphyseallineArticularcartilageSpongy boneCompact boneMedullarycavity Compact boneDiaphysisDistalepiphysis

  • Membranes 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 Sharpeys fibersEndosteumDelicate membrane on internal surfaces of boneAlso contains osteoblasts and osteoclasts

  • Yellow bone marrowEndosteumCompact bonePeriosteumPerforating(Sharpeys) fibersNutrientarteries

  • TrabeculaeBone marrowbetween trabeculaeSpongy bone called diplo in flat bonesStructure of short, irregular and flat bonesPeriosteum-covered compact bone on the outside Endosteum-covers the trabeculae

  • Location of Hematopoietic Tissue (Red Marrow)Red marrow cavities of adultsTrabecular cavities of the heads of the femur and humerusTrabecular cavities of the diplo of flat bonesRed marrow of newborn infantsMedullary cavities and all spaces in spongy bone

  • Osteogenic cellOsteoblastStem cells in periosteum and endosteum that give rise to osteoblastsMatrix-synthesizingcell responsiblefor bone growthMicroscopic Anatomy of Bone

  • Microscopic Anatomy of BoneOsteocyteMature bone cellthat maintains thebone matrixOsteoclastBone-resorbing cell

  • Structuresin thecentralcanalArtery withcapillariesVeinNerve fiberLamellaeCollagenfibersrun indifferentdirectionsTwistingforceCompact Bone: Haversian system, or osteonstructural unitCentral (Haversian) canalContains blood vessels and nervesLamellaeWeight-bearingColumn-like matrix tubes

  • Endosteum lining bony canalsand covering trabeculaePerforating (Volkmanns) canal: Perpendicular to central canal. Connects blood vessels and nerves of the periosteum with central canalPerforating (Sharpeys) fibersPeriosteal blood vesselPeriosteumLacuna (withosteocyte) LacunaeLamellaeNerveVeinArteryCanaliculiOsteocytein a lacunaCircumferentiallamellaeOsteonCentral(Haversian) canalCentralcanalInterstitial lamellaeLamellaeCompactbone Spongy bone

  • Microscopic Anatomy of Bone: Spongy BoneTrabeculaeAlign along lines of stress to resist stressNo osteonsContain irregularly arranged lamellae, osteocytes, and canaliculiCapillaries in endosteum supply nutrients

  • Composition of BoneOrganicOsteogenic cells, osteoblasts, osteocytes, osteoclastsOsteoidorganic bone matrix secreted by osteoblastsGround substance (proteoglycans, glycoproteins)Collagen fibersProvide tensile strength and flexibilityInorganicHydroxyapatites (mineral salts)65% of bone by massMainly calcium phosphate crystalsResponsible for hardness and resistance to compression

  • Bone DevelopmentOsteogenesis (ossification)bone tissue formationStagesBone formationbegins in the 2nd month of developmentPostnatal bone growthuntil early adulthoodBone remodeling and repairlifelong

  • Two Types of OssificationIntramembranous ossificationMembrane bone develops from fibrous membraneForms flat bones, e.g. clavicles and cranial bonesEndochondral ossificationCartilage (endochondral) bone forms by replacing hyaline cartilageForms most of the rest of the skeleton

  • Mesenchymal cellCollagen fiberOssification centerOsteoid (boneMatrix)Osteoblast Ossification centers appear in the fibrous connective tissue membrane. Selected centrally located mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center.1Intramembranous ossificationOsceocytesOsteoidNewly calcified bone matrixOsteoblast Bone matrix (osteoid) is secreted within the fibrous membrane and calcifies. Osteoblasts begin to secrete osteoid, which is calcified within a few days. Trapped osteoblasts become osteocytes.2

  • Mesenchyme condensing to form the periosteumBlood vesselTrabeculae of woven bone Osteoid laid down between blood vessels in a random manner. The result is a network of trabeculae called woven bone. Vascularized mesenchyme condenses and becomes the periosteum.3Fibrous periosteumOsteoblastPlate of compact boneDiplo (spongy bone) cavities contain red marrow Trabeculae just deep to the periosteum thicken, and are later replaced with mature lamellar bone, forming compact bone plates. Spongy bone (diplo), consisting of distinct trabeculae, persists internally and its vascular tissue becomes red marrow.4Woven bone and periosteum form. Lamellar bone replaces woven bone, just deep to the periosteum. Red marrow appears.4

  • Bone collar forms around hyaline cartilage model. Cartilage in the center of the diaphysis calcifies and then develops cavities.Periosteal bud invades the internal cavities and spongy bone begins to form.Diaphysis gets longer, medullary cavity forms, ossification continues. 2o ossification center develops.Epiphyses ossify. After, hyaline cartilage is only in the epiphyseal plates and articular cartilages.Hyaline cartilageArea of deteriorating cartilage matrixEpiphyseal blood vesselSpongy bone formationEpiphyseal plate cartilageSecondary ossification centerBlood vessel of periosteal budMedullary cavityArticular cartilageChildhood to adolescenceBirthWeek 9Month 3Spongy boneBone collarPrimary ossification center12345Endochondral ossificationUses hyaline cartilage blueprintHyaline cartilage breaks downBefore ossification

  • Postnatal Bone GrowthHow bones widen (appositional growth):Osteoblasts beneath periosteum secret bone matrixOsteoclasts on bone surface remove bone

    How bones widenCartilage divide and hypertrophy and are eventually replaced by bone (see next slide)

    Hormonal regulation of bone growth Growth hormone stimulates epiphyseal plate activityThyroid hormone modulates activity of growth hormoneTestosterone and estrogens (at puberty)Promote adolescent growth spurtsEnd growth by inducing epiphyseal plate closure

  • ArticularcartilageBone of epiphysisEpiphyseal plateBone of diaphysisMarrow cavityCartilageCalcified cartilageBoneGH stimulates the lengthening of bones at the epiphyseal plate. GH stimulates osteoblast activity & the proliferation of epiphyseal cartilage. New bone tissue replaces cartilage in this region. GH stimulates bone thickness by activating osteoblasts under the periosteum.

  • CartilageCalcified cartilageBoneRestingchondrocytesEpiphyseal plateDiaphysisBone of epiphysis