bone tissue
DESCRIPTION
BONE TISSUE. DEVELOPMENT and GROWTH. FUNCTIONS. Support/Movement Protection Mineral reservoir Site of blood cell production Storage of fat. Skeletal Cartilage. Consists primarily of water Contains no nerves or blood vessels Surrounded by perichondrium Dense irregular connective tissue - PowerPoint PPT PresentationTRANSCRIPT
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BONE TISSUE
DEVELOPMENT and GROWTH
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FUNCTIONS
• Support/Movement• Protection• Mineral reservoir• Site of blood cell
production• Storage of fat
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Skeletal Cartilage
• Consists primarily of water• Contains no nerves or blood
vessels• Surrounded by perichondrium
– Dense irregular connective tissue– Maintains shape
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Skeletal Cartilage
• Basic components– Chondrocytes in lacunae– Extracellular matrix with jellylike ground
substance• 3 Types
– Hyaline– Elastic– Fibrocartilage
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Hyaline Cartilage
• Most abundant• Fiber not detectable• Locations
• Articular cartilage• Costal cartilage• Respiratory cartilage• Nasal cartilage
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Elastic Cartilage
• Contains more elastic fibers; more flexible• Found in ear and epiglottis
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Fibrocartilage
• Highly compressible• Great strength• Locations
– Knee– Vertebral disks
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Cartilage Growth
• Two methods– Appositional – adds to outside– Interstitial – growth from inside
• Growth stops during adolescence
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Bone Histology - Cell Types
• Osteocytes – mature bone cells – Osteoblasts – bone forming cells – Osteoclasts – bone destroyers
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BONE OSSIFICATION
Process by which tissue becomes bone
Also called osteogenesis
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Bone Formation
• Bone formation begins approx. 8 weeks into fetal development from a skeleton that is mostly fibrous membranes and cartilage
• Intramembranous ossification – bone forms from the fibrous membranes
• Endochondral ossification – bone forms from hyaline cartilage
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Intramembranous Ossification
• Osteoprogenitor (mesenchymal) cells in fibrous C.T. develop into osteoblasts
• Osteoblasts secrete collagen matrix• Calcification occurs in ossification centers;
forming a network of bone rather than layers• Bony plates form which are later converted into
compact bone• Flat bones only; skull & clavicles• Fontanelles are areas not ossified at birth
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ENDOCHONDRAL OSSIFICATION
• Forms most bones• Hyaline cartilage model in shape of the bone
initially; a pH change causes cartilage to calcify and the cells to die
• Primary ossification center forms as blood vessels from periosteum and osteoblasts invade calcified cartilage
• Matrix formed (osteoid= unmineralized bone matrix)• Ossification occurs = calcium salts deposited • Primary centers form before birth; Secondary centers
form 8th month dev.
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Epiphyseal Plate
• Cartilage region between primary and secondary ossification centers
• Responsible for postnatal bone growth• Zone of resting cartilage• Growth Zone – mitosis occurs • Transformation Zone – cartilage matrix
deteriorates• Osteogenic Zone - bone salts deposited
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Calcium regulation
• Calcium is most abundant mineral in the body; 99% located in the bone
• Regulated by two hormones: PTH (parathyroid hormone) and calcitonin
• PTH - raises blood calcium levels• Calcitonin - lowers blood calcium levels
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Hormones and Vitamin Effect on Bone Growth
• Testosterone• Estrogen• Growth Hormone• Throxine - • Vitamin D – calcium absorption
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Bone Types• Compact Bone
– also called dense bone
– hard, strong and solid bone that forms the outer layer of all bone
– provides support, protection and resists stress
• Contains osteons
• Cancellous – also called spongy
bone– found more toward
the inner portion of bone
– open lattice-work of struts and plates that serves to store bone marrow
• Trabeculae
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Osteons = Haversian System
• Haversian canal • Volkmann’s
canals• Lamellae• Lacunae• Canaliculi
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Bone Types
• Long – arms and legs• Short – wrist and ankle
– Sesamoid – forms within a tendon (patella)
• Flat – sternum, scapula, ribs, skull• Irregular – vertebrae & coxal bones
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Structure of a Long Bone
• Diaphysis• Epiphysis• Articular cartilage• Periosteum – connective tissue covering bone• Medullary cavity• Endosteum – connective tissue; lines inside
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Bone Fractures
• Open ( Compound) – penetrates skin
• Closed (Simple)• Partial/Complete - Greenstick• Comminuted – broken into 3 or
more pieces
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Bone Repair
• Formation of clot ( hematoma)• Callus ( soft followed by hard) • Mineralization of callus by calcium &
phosphorus• Remodeling