Bone histology：骨组织学

1、BONE PATHOLOGYBONE PATHOLOGYDariusz Borys MDOBJECTIVESOBJECTIVES Identify main functions of bone tissue Identify the major parts of a long bones Describe the cells found in bone tissue Describe the components of an osteon Compare and contrast intramembranous and endochondral ossification.BONE FUNCTI

2、ONBONE FUNCTION Support Protection (protect internal organs) Movement (provide leverage system for skeletal muscles, tendons, ligaments and joints) Mineral homeostasis (bones act as reserves of minerals important for the body like calcium or phosphorus) Hematopoiesis: blood cell formation Storage of

3、 adipose tissue: yellow marrow SHAPE OF BONESSHAPE OF BONESLong bones (e.g., humerus, femur)Short bones (e.g., carpals, tarsals, patella)Flat bones (e.g., parietal bone, scapula, sternum)Irregular bones (e.g., vertebrae, hip bones)BONE ANATOMYDiaphysis: long shaft of boneEpiphysis: ends of boneEpiph

4、yseal plate: growth plateMetaphysis: b/w epiphysis and diaphysisArticular cartilage: covers epiphysisPeriosteum: bone covering (pain sensitive)Sharpeys fibers: periosteum attaches to underlying boneMedullary cavity: Hollow chamber in bone- red marrow produces blood cells- yellow marrow is adiposeEnd

5、osteum: thin layer lining the medullary cavityBLOOD AND NERVE SUPPLY OF BONEBLOOD AND NERVE SUPPLY OF BONE Bone is supplied with blood by: Periosteal arteries accompanied by nerves supply the periosteum and compact bone Epiphyseal veins carry blood away from long bones Nerves accompany the blood ves

6、sels that supply bones The periosteum is rich in sensory nerves sensitive to tearing or tensionLONG BONESLONG BONESCompact Bone dense outer layerSpongy Bone (cancellous bone) honeycomb of trabeculae (needle-like or flat pieces) filled with bone marrowCOMPACT BONE: (OSTEON) EXTERNAL LAYERCOMPACT BONE

7、: (OSTEON) EXTERNAL LAYER- called lamellar bone (groups of elongated tubules called lamella)- majority of all long bones- protection and strength (wt. bearing)- concentric ring structure- blood vessels and nerves penetrate periosteum through horizontal openings called perforating (Volkmanns) canals.

8、COMPACT BONE: (OSTEON) EXTERNAL LAYERCOMPACT BONE: (OSTEON) EXTERNAL LAYER Central (Haversian) canals run longitudinally. Blood vessels and nerves.- around canals are concentric lamella- osteocytes occupy lacunae which are between the lamella- radiating from the lacunea are channels called canalicul

9、i (finger like processes of osteocytes)COMPACT BONECOMPACT BONE- Lacunae are connected to one another by canaliculi- Osteon contains: - central canal- surrounding lamellae- lacunae- osteocytes- canaliculiSPONGY BONE (CANCELLOUS BONE): INTERNAL SPONGY BONE (CANCELLOUS BONE): INTERNAL LAYERLAYER- trab

10、ecular bone tissue (haphazard arrangement).- filled with red and yellow bone marrow- osteocytes get nutrients directly from circulating blood.- short, flat and irregular bone is made up of mostly spongy boneHISTOLOGY OF BONEHISTOLOGY OF BONE Histology of bone tissueCells are surrounded by matrix.- 2

11、5% water- 25% protein- 50% mineral salts4 cell types make up osseous tissueOsteoprogenitor cellsOsteoblastsOsteocytesOsteoclastsCells of Bone Tissue Osteoprogenitor cells:- derived from mesenchyme- all connective tissue is derived- unspecialized stem cells- undergo mitosis and develop into osteoblas

12、ts- found on inner surface of periosteum and endosteum.Cells of Bone Tissue Osteoblasts:- bone forming cells- found on surface of bone (arrow)- no ability to mitotically divide- collagen secretors Osteocytes: - mature bone cells- derived form osteoblasts- do not secrete matrix material- cellular dut

13、ies include exchange of nutrients and waste with blood. Osteoclasts- bone resorbing cells- bone surface- growth, maintenance and bone repairAbundant inorganic mineral salts:- Tricalcium phosphate in crystalline form called hydroxyapatite Ca3(PO4)2(OH)2- Calcium Carbonate: CaCO3- Magnesium Hydroxide:

14、 Mg(OH)2- Fluoride and SulfateSKELETAL CARTILAGESKELETAL CARTILAGE Chondrocytes: cartilage producing cells. Lacunae: small cavities where the chondrocytes are encased. Extracellular matrix: jellylike ground substance. Perichondrium: layer of dense irregular connective tissue that surrounds the carti

15、lage. No blood vessels or nervesTypes of Cartilage Hyaline cartilage (glassy) Most abundant cartilage Provides support through flexibility Articular cartilages and costal cartilage, larynx, trachea, and nose Elastic cartilage contains many elastic fibers Able to tolerate repeated bending Ear and epi

16、glottis Fibrocartilage resists strong compression and strong tension An intermediate between hyaline and elastic cartilage Intervertebral discs and pubic symphysisBONE FORMATIONBONE FORMATIONThe process of bone formation is called ossificationBone formation occurs in four situations: 1) Formation of

17、 bone in an embryo 2) Growth of bones until adulthood 3) Remodeling of bone 4) Repair of fracturesBone Formation Formation of Bone in an Embryo cartilage formation and ossification occurs during the sixth week of embryonic development two patterns Intramembranous ossification Flat bones of the skull

18、 and mandible are formed in this way “Soft spots” that help the fetal skull pass through the birth canal later become ossified forming the skull Endochondral ossification The replacement of cartilage by bone Most bones of the body are formed in this way including long bonesIntramembranous Ossificati

19、on An ossification center appears in the fibrous connective tissue membrane Osteoblasts secrete bone matrix within the fibrous membrane Osteoblasts mature into osteocytesEnlargingchondrocytes withincalcifying matrixChondrocytes at the center of the growing cartilage model enlarge and then die as the

20、 matrix calicifies.Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of bone.Blood vessels penetrate the cartilage. New osteoblasts form a primary ossification center.The bone of the shaft thickens, and the cartilage near each epiphysis is replaced by shafts of bone.Blood ve

21、ssels invade the epiphyses and osteo-blasts form secondary centers of ossification.CartilagemodelBoneformationEpiphysisDiaphysisMarrowcavityPrimaryossificationcenterBloodvesselMarrowcavityBloodvesselSecondaryossificationcenterEpiphysealcartilageArticularcartilageReplacement of hyaline cartilage with

22、 boneMost bones are formed this way (i.e. long bones).Endochondral OssificationLongitudinal Bone Growth Longitudinal Growth (interstitial) cartilage continually grows and is replaced by bone Bones lengthen entirely by growth of the epiphyseal plates Cartilage is replaced with bone as quickly as it g

23、rows Epiphyseal plate maintains constant thicknessGROWTH IN LENGTHGROWTH IN LENGTH The growth in length of long bones involves two major events: Growth of cartilage on the epiphyseal plate Replacement of cartilage by bone tissue in the epiphyseal plate - osteoblasts located beneath the periosteum se

24、crete bone matrix and build bone on the surface - osteoclasts located in the endosteum resorbs (breakdown) bone.GROWTH OF CARTILAGE ON THE EPIPHYSEAL PLATE- epiphyseal plate (bone length)- 4 zones of bone growth under hGH.1- Zone of resting cartilage (quiescent):- no bone growth- located near the ep

25、iphyseal plate- scattered chondrocytes- anchors plate to bone2- Zone of proliferating cartilage (prolferation zone) - chondrocytes stacked like coins- chondrocytes divide3- Zone of hypertrophic (maturing) cartilage- large chondrocytes arranged in columns- lengthwise expansion of epiphyseal plate4- Z

26、one of calcified cartilage- few cell layers thick- occupied by osteoblasts and osteoclasts and capillaries from the diaphysis- cells lay down bone- dead chondrocytes surrounded by a calcified matrix. Matrix resembles long spicules of calcified cartilage. Spicules are partly eroded by osteoclasts and

27、 then covered in bone matrix from osteoblasts: spongy bone is formed. APPOSITIONAL BONE GROWTH Growing bones widen as they lengthen Appositional growth growth of a bone by addition of bone tissue to its surface Bone is resorbed at endosteal surface and added at periosteal surface Osteoblasts add bone tissue to the external surface of the diaphysis Osteoclasts remove bone from the internal surface of the diaphysisFigure 6-6BONE REMODELINGBONE REMODELING- bone continually renews itself- never metabolically at rest- enables Ca to be pulled from bone when blood levels are low- osteoclasts ar