BONE STRUCTURE

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Histological structure

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What is Bone? – Mineralized connective tissue:

What is Bone? – Mineralized connective tissue BONE CELLS Osteoprogenitor cells Osteoblasts Osteocytes Osteoclasts MATRIX 1. Organic (1/3) Type I collagen ( 95% ) Ground substance - glycosamino- glycans , Bone proteins 2. Inorganic (2/3) Inorganic salts

Bone cells:

Bone cells Osteo progenitors (Pleuripotent stem cells) Osteoblasts ("bone makers") Osteocytes ("bone cells") Osteoclasts (“bone breakers”) remodeling MATRIX Ground substance Proteoglycans Glycoproteins Minerals Water Fibers

Cells of Bone (Primary/Temporary):

Cells of Bone (Primary/Temporary) Osteoprogenitor Osteoclast Osteoblast Osteocyte Osteoid

Bone cells -Function:

Bone cells -Function Osteoblasts – Matrix synthesis – Osteoid, Calcification PTH receptors Osteocyte – Maintanace of Matrix Osteoclast – Digestion of collagen, dissolving hydroxy apatite Calcitonin receptors BONE TUMOURS OSTESARCOMA METASTASES – Breast, lungs, kidney, prostate,thyroid

Bone cells- Medical application:

Bone cells- Medical application Rate of bone apposition – Bone growth Osteomalacia – Impaired mineralization Osteitis fibrosa cystica – osteoclast activity Osteopetrosis – “Marble bones” – Bone resorption defect Osteitis deformans (Paget’s disease) –Uncontrolled osteoclast activity followed by osteoblastic activity (incomplete)- Stops at osteoid level

Matrix:

Matrix Fibers – Collage Type I- Gene mutation in alfa 1or 2 OSTEOGENESIS IMPERFACTA Ground substance Proteoglycans – Chondroitin 4/6 Sulphate , Keratan Sulphate Glycoproteins – Osteocalcinin , Alkaline phosphatase Minerals – Calcium, Phosphate Water

Is Bone inert material or living tissue?:

Is Bone inert material or living tissue? FEATURES Vascularity Pattern of growth Subjected to disease Heals after injury Regenerative power Molding nature Disuse atrophy Overuse hypertrophy FUNCTIONS Supportive -structural frame work, attachment Movement -Lever Protection Blood cells Production Mineral storage Ca and P Storage of energy Immunological

Classification:

Classification REGION - Axial, Appendicular SHAPE - Long bones, short bones, irregular, pneumatic, sesamoid , accessory STRUCTURE Macroscopic – Compact Spongy Microscopic – Lamellar (Secondary Bone) Woven/fibrous (Primary Bone) DEVELOPMENT – Membranous Cartilaginous Membrano -cartilaginous

Structural regions of long bone:

Structural regions of long bone

Gross structure of typical long bone:

Gross structure of typical long bone Shaft – Thick compact bone+ medullary cavity Ends- Cancellous bone + thin compact layer Articular cartilage – No periosteum , avascular Periosteum – Fibrous + cellular Shape, nutrition, attachment fracture repair, sensitive Endosteum – Cellular -Repair and remodelling Nutrient foramen – mid shaft Bone marrow – Red, Yellow

Parts of a growing bone:

Parts of a growing bone Epiphysis (Secondary) Epiphyseal plate Metaphysis Diaphysis (Primary)

Types of Epiphyses:

Types of Epiphyses PRESSURE Articular Wt. transmission TRACTION Non-articular Muscle pull Ossifies later than Pressure ATAVASTIC Parasite ABERRANT Unusual

Metaphysis:

Metaphysis Epiphyseal end of diaphysis Active growth Before fusion end arteries, hair pin bends OSTEOMYELITIS

Blood supply of bones:

Blood supply of bones Long Bone Nutrient artery Metaphyseal arteries Epiphyseal arteries Periopsteal arteries Short Bone - Nutrient artery; Periopsteal arteries Vertebra - Body, Processes Rib - Nutrient artery; Periopsteal arteries

Nutrient artery:

Nutrient artery Mid shaft Tortuiosity 2/3 rd inner compact bone Hair pin loops Direction – away from growing end “To the elbow I go. From the knee I flee.”

Epiphyseal arteries:

Epiphyseal arteries Articular and epipyseal cartilages - continuous AVASCULAR NECROSIS Articular and epipyseal cartilages - not continuous

PowerPoint Presentation:

Spongy Bone- No HS

Osteon (Haversian system) :

Osteon (Haversian system) Central canal ( H aversian or osteonal canal) Transverse (Volkmann) canals Lacuna (pl. lacunae) Canaliculi ("tiny canals ") Lamellae (sing. lamella) Concentric,Intersititial , Circumferential

Compact bone:

Compact bone

COMPACT BONE:

COMPACT BONE

Sharpey’s fibers:

Sharpey’s fibers Connective tissue matrix Bundles of collagen fibers Connect Perisoteum to Bone Fibrous layer of Periosteum to outer circumferential and interstitial lamellae

Spongy Bone:

Spongy Bone Superimposed lamllae No Haversian system Lamellated trabeculae Red marrow

Lines of stresses:

Lines of stresses Wolf’s Law :Orientation of trabeculae Pressure lamellae – Lines of wt. transmission Tension lamellae – right angles to PL Realignment of new lines after #

Intramembranous Ossification:

Intramembranous Ossification CLEIDO-CRANIAL DYSOSTOSIS

Endochondral Ossification:

Endochondral Ossification

Endochondral Ossification:

Endochondral Ossification

Endochondral Ossification Defects – AD Inheritance:

Endochondral Ossification Defects – AD Inheritance Achondroplasia Thanatophoric Dysplasia Hypochondroplasia Mutation in FGFR 3 gene

Growing Bone:

Growing Bone BONE GROWTH 1. Appositional 2. Endochondral

Growth Plate:

Growth Plate

Zone of reserve cells Zone of Proliferation Zone of Hypertrophy Zone of calcification :

Zone of reserve cells Zone of Proliferation Zone of Hypertrophy Zone of calcification

Factors affecting growth of a bone:

Factors affecting growth of a bone Nutritional – Vit . A - Co-ordination of osteoblastic and osteoclastic activity Vit.C – Synthesis of organic matrix Vit.D – Absorption of Ca , P Rickets, Osteomalacia (Calcification deficiency) Calcium – Decalcification of bone Genetic factors – Chondro dystrophic foetalis

Factors affecting growth of a bone:

Factors affecting growth of a bone Hormonal – Pituitary - GH – Dwarfism; Gigantism, Acromegaly Thyroid - Calcitonin Parathyroid – PTH Decalcification Sex Hormones - Androgens, estrogens - Stimulators Mechanical factors Tensile forces – Bone formation Compressive forces – Bone resorption

Ossification Centre:

Ossification Centre

Rules of Ossification:

Rules of Ossification Primary centers - before birth except carpal and tarsal (except calcaneus, talus, cuboid) Secondary centers - after birth except lower end of femur, upper end of tibia, humerus C enter which appears first unites last except lower end if FIBULA

Rules of Ossification:

Rules of Ossification Center which appears later unites first except upper end of fibula Direction of nutrient artery - away from growing end except fibula Growing end is one where center appears first and unites last except fibula

Fracture Healing:

Fracture Healing Hematoma formation Macrophages Osteoclasts 2. Fibrocartilaginous callus formation Periosteum Endosteum 3. Bony callus formation Ossification (EC & IM) 4. Remodeling Sec.bone formation

Bone remodeling cycle:

Bone remodeling cycle

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