BONES AND BONE TISSUES(学习资料).ppt

,BONES AND BONE TISSUES,CHAPTER 69/16/07,Introduction,One of the most remarkable tissues of the human bodyFar from inert and lifeless,bones are living,dynamic structuresBones serve a wide variety of very diverse functions within usNoted for their strength and resiliency during life,bones will remain long after we are gone,Chapter Outline,Skeletal cartilagesBonesDisorders of bonesThe skeleton throughout life,Location and Basic Structure,Cartilages are found throughout the adult human body,Location and Basic Structure,Initially our skeleton is made up of fast growing cartilages and fibrous membranesGradually our skeletal cartilages are replaced by boneUpon reaching adulthood the skeleton becomes almost fully ossifiedOnly a few cartilages remain in the adult skeleton,Location and Basic Structure,A typical cartilage is composed of connective tissue cartilageIt contains no nerves or blood vesselsIt is surrounded by a layer of dense irregular connective tissue called the perichondrium which resists outward expansion of the tissue when subjected to pressure,Location and Basic Structure,Each type of cartilage contains a high proportion of water which makes them resilient after compressionCartilage is 60-80%waterThe water allows nutrients to diffuse rapidly through a loose matrix,Basic structure,type&location,There are three types of cartilage tissue:hyaline,elastic,and fibrocartilageEach type consists of chondrocytes living in an extracellular matrixEach contains a matrix of jellylike ground substance of complex sugar molecules that attract and hold water that is laced with connective tissue fibers,Hyaline cartilages,The most prevalent type of cartilage Its high proportion of collagen fibers give it flexibility and resilience while providing supportUpon examination the tissue appears white,frosted,and smooth,Hyaline cartilages,The chondrocytes appear spherical Each chondrocyte occupies a cavity in the matrix called a lacuna The only type of fiber in the matrix is a collagen unit fibril,Hyaline cartilage locations,Articular-covers the end of bonesCostal-connect ribs to breastboneLaryngeal-skeleton of larynxTracheal&bronchial-reinforce the respiratory passagesFetal-forms the embryonic skeleton,Elastic cartilage,Elastic cartilage is similar to hyaline cartilage but its matrix contains many more elastic fibers in addition to collagen fibersIts elastic fibers enable it to withstand repeated bendingFound only in the external ear and the epiglottis,Fibrocartilage,The tissue consists of parallel rows of thick collagen fibers alternating with rows of chondrocytesTissue is highly compressible and has great tensile strengthFound in thick pad-like structures like the menisci of the knee or the discs of the vertebral column,Growth of Cartilage,A cartilage grows in two waysAppositional growth occurs when cells in the surrounding perichondrium secrete new matrix next to existing cartilage tissue(growth from the outside)Interstitial growth occurs when the chondrocytes within the cartilage divide and secrete new matrix,expanding the cartilage(growth from within),Growth of Cartilage,Cartilage stops growing in the late teens when the skeleton itself stops growingChondrocytes stop dividing and growth stopsCartilage regenerates poorly in adults with most of the“healing”reflecting the ability of the remaining chondrocytes to secrete additional extracellular matrix,BONES,SECTION II,Bones,Bones of the skeleton are organs that contain several different tissuesBones are dominated by bone tissue but also contain Nervous tissue and nervesBlood tissue and vesselsCartilage in articular cartilagesEpithelial tissue lining the blood vessels,Function of Bones:,Bones perform several important functions:SupportMovement ProtectionMineral storage Blood cell formation and energy storage,Function of Bones,Support,Bones provide a hard framework that supports the body Bones provide support for internal organs,Function of Bone,Movement,Skeletal muscle attached to bones use the bones as levers to move the bodyArrangement of bones and joints determine the movements possible,Function of Bone,Protection,Fused bones provide a brain case that protects this vital tissueSpinal cord is surrounded by vertebraeRib cage protects vital organs,Function of Bones,Mineral Storage,Bone serves as a mineral reservoirPhosphate and calcium ions can be released into the blood steam for distributionDeposition and removal are ongoing,Function of Bones,Blood cell formation,Hematopoiesis occurs within the red marrow cavities of the long bonesThe yellow marrow cavities are involved in fat storage,CLASSIFICATION OF BONE,SECTION III,Classification of Bone:,Bones vary in shape and sizeThe unique shape of each bone fulfills a particular needBones are classified by their shape as long,short,flat,or irregular boneBones differ in the distribution of compact and spongy osseous tissues,Classification of Bones,Classification:Long Bone,Long bones have a long shaft and two distinct endsClassification is based on shape not sizeCompact bone on exterior w/spongy on the interior,Classification:Short Bones,Short bones are roughly cubelikeThin compact bone layer surrounding spongy bone massShort bones are often carpal,tarsal and sesamoid bones,Classification:Flat Bones,Flat bones are thin,flattened and usually curvedParallel layer of compact bone with spongy bone layer betweenSkull,sternum and ribs are examples,Classification:Irregular Bone,Irregular bones dont fit into the previous categoriesComplicated shapesConsist of spongy bone with a thin layer of compactExamples are hip bones&vertebrae,Gross Anatomy of Bones,SECTION IV,Gross Anatomy,LandmarksDiaphysis Proximal epiphysisDistal epiphysisMembranesPeriosteumEndosteum,Diaphysis,Long tubular diaphysis is the shaft of the boneCollar of compact bone surrounds a central medullary or marrow cavityIn adults,cavity contains fat,Epiphysis,The epiphyses are the ends of the boneThe joint surface of the epiphysis is covered with articular cartilageEpiphyseal line separate diaphysis and epiphysis,Blood Vessels,Unlike cartilage bone is well vascularizedNutrient arteries serve the diaphysisThe nutrient artery runs inward to supply the bone marrow and the spongy bony,Medullary cavity,The interior of all bones consists largely of spongy boneThe very center of the bone is an open or marrow cavityThe cavity is filled with yellow bone marrow,Membranes,Periosteum covers outer bone surfaces except the ends of the epiphysisThe membrane has two sublayersSuperficial layerOsteogenic layer,Membranes,The superficial layer consists of dense irregular connective tissue which resists tension placed on a bone during bendingThe osteogenic layer abuts the compact bone and contains bone-depositing cells called osteoblasts and osteoclasts that are responsible for bone remodeling,Membranes,During periods of bone growth or deposition the osteogenic cells differentiate into osteoblastsOsteoblasts produce the bone tissue that forms the circumferential lamellae that encircle the perimeter of the bone,Membranes,Periosteum is richly supplied with nerves and blood vesselsThe periosteum is supplied by branches of the nutrient artery and epiphyseal vessels,Membranes,The periosteum is secured to the underlying bone by perforating fibers(Sharpeys fibers)Thick bundles of collagen fibers run from the periosteum into the bone matrix,Membranes,Internal bone structures are covered by a thinner connective tissue membrane the endosteumIt also contains the osteoclasts and osteoblasts necessary for bone remodeling,Membranes,The endosteum covers the trabeculae of spongy bone and lines the central canals of osteons,Short,Irregular and Flat Bones,Bones consist of thin layers of compact bones over spongy boneNo shaft,epiphysis or marrow cavitySpongy area between is a diploeFlat sandwich of bone is common in bones of skull,Bone Design and Stress,The internal anatomy of each bone reflects the stresses most commonly placed upon itBones are subjected to compressive forces in weight bearing and tension forces when muscle pulls upon themOften weight bearing loads are applied off center which threatened to bend the bone,Bone Design and Stress,Bending compresses the bone on one side and compresses it on the otherCompression and tension are greatest at the external surfaces of the bone,Bone Design and Stress,Compact bone occurs at the external surfaces to resist these tension and compression forcesInternal bone structures are not subjected to these forces and thus spongy bone is sufficient,Bone Design and Stress,As there are only limited tension and compression forces at the bones center the hollow medullary cavity does not impact a long bones weight bearing capacity,Bone Design and Stress,Spongy bone is not a random network of bone fragmentsThe trabeculae align along stress lines in an organized patterns of tiny struts that provide internal support for the bone,Bone Markings,Bones are shaped by the tissues that act upon and around themBones display bulges,depressions and holes which serve as sites of muscle,ligament and tendon attachment,points of articulation,or as conduits for blood vessels and nervesProjections from the bone surface include heads,trochanters,spines,and othersDepressions include fossae,sinuses,foramina,and grooves,Bone Markings,Tuberosity-a large rounded projection which may be roughenedtibial tuberosity,Bone Markings,Crest-A narrow ridge of bone;usually prominentCrest of the ilium,Bone Markings,Trochanter-A very large,blunt,irregularly shaped processGreater trochanter of femur,Bone Markings,Line-Narrow ridge of bone;less prominent than a crestIntertrochanteric line,Bone Markings,Tubercle-Small rounded projection or processadductor tubercle,Bone Markings,Epicondyle-raised area on or above a condylemedial epicondyle of the humerous,Bone Markings,Spine-A sharp,slender,often pointed projectionSpinous process of vertebrae,Bone Markings,Head-Bony expansion carried on a narrow neckhead of the humerus,Bone Markings,Facet-Smooth,nearly flat articular surfacefacet on transverse process of thoracic vertebrae,Facet,Bone Markings,Condyle-Rounded articular projectionlateral condyle of femur,Bone Markings,Ramus-Armlike bar of boneramus of the pubis,Bone Markings,Meatus-canal-like passagewayExternal auditory meatus,Bone Markings,Sinus-Cavity within a bone,filled with air and lined with mucous membranenasal sinus,Bone Markings,Fossa-Shallow,basinlike depression in a bone often serving as an articular surfaceOlecranon fossa,Bone Markings,Groove-a narrow furrow in the surface of the boneradial groove,Bone Markings,Fissure-Narrow,slitlike opening,Bone Markings,Foramen-Round or oval opeing through a boneForamen magnum,Compact Bone,Compact bone appears very denseIt actually contains canals and passageways that provide access for nerves,blood vessels,and lymphatic ducts The structural unit of compact bone is the osteon or Haversian systemEach osteon is an elongated cylinder running parallel to the long axis of the boneFunctinally each osteon represents a weight bearing pillar,Compact bone,Compact Bone,Structurally,an osteon is a group of concentric rings of bone tissue surrounding a central canalEach of the concentric rings called lamella is a layer of bone matrix in which the collagen fibers and mineral crystals align and run in a single directionFibers of adjacent lamella run in roughly opposite direction,Compact bone,Compact bone,An Osteon,Each osteon is a group of hollow tubes of bone matrixEach matrix tube contain lamellaCollagen fibers in each layer run in opposite directionsOrientation resists torsion stresses,Compact Bone,The alternating pattern of lamella orientation is optimal for withstanding torsion,stressesThe lamella of bone also inhibit crack propagationWhen a crack reaches the edge of a lamella,the forces causing the crack are dispersed around lamellar boundaries,thus preventing the crack from progressing into deeper parts of the bone and causing fracture,An Osteon,Running through the core of each osteon is the central or Haversian canalThe canal contains small blood vessels that supply the cells of the osteon,Central or Haversian Canal,The canal is lined by endosteumThe canal contains the blood supply for the osteon,Perforating(Volkmanns)Canal,Canals lie at right angles to long axis of boneConnect the vascular supply of the periosteum to those of the central canal and medullary cavity,Compact Bone,Osteocytes are the mature bone cells occupying the small spaces in the solid matrix called lacunaThin tubes called canaliculi run through the matrix connecting,Compact Bone,Osteocytes occupy small cavities or lacuna at the junctions of lamellaFine canals called canaliculi connect the lacuna to each other and to the central canalCanaliculi tie all the osteocytes in an osteon together,Compact Bone,Canaliculi run through the matrix connecting neighboring lacunae to one another and to the nearest capillaries such as those in the central canalWithin the canaliculi,the extensions of neighboring osteocytes touch each other and form gap junctions,Compact Bone,Gap junctions allow nutrients diffusing from the capillaries to cross these junctionsNutrients are then passed from one osteocyte to the next,Compact Bone,The passage of nutrients through gap junctions occurs throughout an entire osteonThis direct transfer from cell to cell is the only way to supply osteocytes with nutrients as the intervening bone matrix is too solid and impermeable to act as a diffusion medium,Compact Bone,Osteocytes remain in the matrix they have secretedLive cells appear to be needed to maintain the matrixLoss of osteocytes from the matrix results resorbtion of the matrix,Compact Bone,Not all lamellae in compact bone occur in osteonsInterstitial lamellae are incomplete lamellae lying between the cylindrical osteonsThese represent remnants old osteons cut by bone remodeling,Spongy Bone,Spongy bone occurs at the ends of long bones and surrounding the medullary cavityIt is less dense and complex than compact bone,Spongy Bone,Trabeculae are the dominate feature Trabeculae contain irregularly arranged lamallae and osteo-cytes interconnected by canaliculiThere are no osteons presentOsteocytes receive nutrients from capillaries in endosteum,Spongy Bone,Trabeculae align along lines of stressFunction as struts of bone,Chemical Composition of Bone,The organic components of bone are:Osteoblasts(bud cells)Osteocytes(mature cells)Osteoclasts(large cells which resorb matrix)Osteoid(organic part of the matrix)Osteoid makes up 1/3 of the matrixIncludes proteogylcans,glycoproteins,&collagenThese components,particularly collagen contribute to the flexibility and tensile strength of bone to resist stretching and twisting,Chemical Composition of Bone,The inorganic components of bone(65%by mass)consist of hydroxyapatites or mineral salts,largely calcium phosphateTiny crystals of calcium salts are deposited in and around the collagen fibers of the extracellular matrix