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BONE HISTOLOGY
Ma. Minda Luz M. Manuguid M.D.
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Osseous tissue
BONE is a specialized form ofconnective tissue composed of
specialized cells (Osteocytes)enclosed within shallow depressions(lacunae) widely scattered in a tough
organic matrix in which minerals havebeen precipitated.
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characteristics
composition: 20-30% organic matter;25% water; 40-50% inorganic
matter high tensile & compressive strength relatively lightweight; has some
elasticity dynamic tissue constantly
undergoing resorption & renewal
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functions
provide (with Cartilage) mechanicalsupport & protection of other
organs especially within the skull &
thoracic cage principal internal support of the body rigid structures for attachment of
tendons & muscles --- movement;locomotion
mobilizable storage depot for Calcium marrow is hematopoietic
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Bone components
parenchymal cells: OSTEOCYTES andOSTEOPROGENITOR CELLS;OSTEOBLASTS;
OSTEOCLASTS matrix/ extracellular fibers : OSSEIN
matrix/extracellular ground substance
inorganic: (mineralized) HYDROXYAPATITEcrystals organic: OSTEOID: Glycosaminoglycans,
Glycoproteins: KERATAN SULFATE;CHONDROITIN SULFATE; HYALURONIC
ACID
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Bone cells
OSTEOPROGENITOR CELLSrelatively undifferentiated
found on all free surfaces of Boneactive during normal bone growthpale oval to elongated nucleusacidophilic to faintly basophilic cytoplasm
active during normal bone growth & duringadult reorganization
can transform into Osteoblasts
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Bone cells
OSTEOBLASTS bone-forming cells found on the
advancing surfaces of growing bone ovoid nucleus with prominent nucleolus basophilic cytoplasm with extensive ER,
many ribosomes, numerous elongatedmitochondria, & well-developed Golgi
(+) alkaline phosphatase secrete bone matrix (osteoid) converted to Osteocytes
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Bone cells
OSTEOCYTES main parenchymal cells of mature bone
flattened, found inside lacunae with numerous fine processes insidecanaliculi radiating outward,communicating with other canaliculi &
with Haversian or Volkmanns canals can still secrete osteoid but to a lesser
degree than osteoblasts
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Bone cells
OSTEOCLASTS phagocytic, bone-destroying cells
multinucleated, syncitial formed bycoalescence/fusion of severalmacrophage-type cells; may have up to50 nuclei
associated with Howshipslacunae (+) acid phosphatase
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Bone matrix
Extracellular fibers type I collagen, 50-70 nm in diameter, in
cross-linkages of 67 nm periodicity called OSSEIN bone collagen
Amorphous ground substance organic: OSTEOID: Keratan sulfate,
Chondroitin sulfate, Hyaluronic acid
inorganic: HYDROXYAPATITE crystals(Ca PO4 OH ); Ca carbonate, Mg, F, Na,Citrate; may be extracted by a weakacid/chelating agent
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Bone morphology
Gross: Long bones femur, humerus,
Flat bones skull bones Short bones carpals, tarsals, Irregular bones patella,
ossicles
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BONE MORPHOLOGY:GROSS
Periosteum - outer coveringSharpeys fibers
Epiphysis - endsEpiphyseal Plate hyaline
cartilage - region of verticalgrowth of long bones
Metaphysis - broad neck areaDiaphysis shaftMarrow CavityEndosteum inner covering
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Parts of a Long bone
DIAPHYSIS shaft thick-walled hollowcylinder of compact bone with voluminouscentral medullary cavity
EPIPHYSIS end spongy bone covered bya thin peripheral cortex of compact bone;Epiphyseal plate- cartilage betweenepiphysis & diaphysis, only seen in growingbones
METAPHYSIS columns of spongy bonewhich unite the epiphyseal plate to thediaphysis
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Bone coverings
PERIOSTEUM / PERICRANIUM outerdense irregular connective tissue; inner layerof osteoblastsSharpeys fibers- coarse bundles of
collagenous fibers from the periosteum whichturn inward to penetrate the outercircumferential lamellae, anchoring theperiosteum to the underlying bone; especiallynumerous in skull bones
ENDOSTEUM / DURA MATER thin cellularmembrane lining the marrow cavity & thecavities between trabeculae of spongy bone
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BONE MORPHOLOGY:
MICROSCOPICMicroscopic:Compact bone Substantia compacta
apparently solid/continuous but containsmicroscopic spacesCancellous/Spongy bone Substantia
spongiosa 3dimensional lattice ofbranching bony spicules/trabeculaedelimiting a labyrinthine system ofintercommunicating spaces occupied bybone marrow.
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BONE MORPHOLOGY
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BONE HISTOLOGY
COMPACT BONE:Haversian
system/OSTEONLamellae layers of
osteocytes & bone matrixHaversian canals lie
parallel to long axis ofbone
Volkmanns canals oblique/ horizontal
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BONE MORPHOLOGY:MICROSCOPIC
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Bone histology
Lamella: Haversian lamellae- concentrically
arranged lamellae around alongitudinal vascular channel: 4 20 /osteon
interstitial/angular lamellae-irregular lamellae between osteons
inner circumferential lamellae justbeneath the endosteum outer circumferential lamellae just beneath the periosteum
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Bone histology
Lacunae - lenticular cavitieshousing bone cells
Canaliculi - slender tubularpassages radiating from lacunae &penetrating the interstitialsubstance to anastomose withother canaliculi & vascular spaces
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Bone histology
CANCELLOUS BONETrabeculaeBone marrow
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Cancellous (spongy) bone
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Bone marrow
Bone marrow- a mixture ofadipose & hematopoietic cells
Platelet precursors: megakaryoblasts
RBC precursors: Erythroblasts / normoblasts Reticulocytes
WBC precursors:
myeloblasts Lymphoblasts Monoblasts
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Bone marrow
Platelet precursors:MegakaryoblastsMegakaryocytes
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Osteogenesis
Bone is formed from periosteal osteoblastsor from pre-existing connective tissue, mostcommonly hyaline cartilage
Endochondral ossificationIntramembranous ossification - periosteal bonegrowth
Hormonal requirements: parathormone,
growth hormone,Nutritional requirements:Vitamins C, D & minerals, esp CaProtein
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Endochondral ossification
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Endochondral ossificaton
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Calcium metabolism &
bone remodelingHormone controlParathormone secreted by the chief cells
of the parathyroid gland, it promotes release
of Calcium from bone, thus raising blood CalevelsCalcitonin secreted by the parafollicular
C cells of the thyroid gland, it promotesincorporation of Calcium into bone, thus
lowering blood Ca levelsOther hormones: GH, Thyroxine, Estrogen
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Bone remodeling
Nutritional requirements:Proteins
Vitamins: A, C, DMinerals: Ca, PO4
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Bone disorders
Osteoporosis poor mineralization ofbone due to deficiency of Calcium
Osteomalacia / Rickets softening or
demineralization of bone due to adeficiency of vitamin D in adults /children (bone deformities may
become permanent)
Osteoma benign bone growthOsteosarcoma malignant neoplasm ofbone
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Thats all !