bones and skeletal tissue chapter 6. objectives know the functions of the skeletal system understand...
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Objectives• Know the functions of the skeletal system
• Understand how bones are classified
• Identify the macroscopic and microscopic features of bone
• Understand how bone is developed
• Know what a fracture is and how it is repaired
• Know some bone disorders
Skeletal System• Composed of bones, cartilages, and ligaments joined tightly
together to form a strong, flexible framework for the body
• Skeleton functions– Support – Protection– Movement – Electrolyte balance – Acid-base balance– Blood formation
• Osseous tissue– Connective tissue with a hardened matrix
• Deposition of calcium phosphate and other minerals– Part of the composition of a bone
http://www.amersol.edu.pe/class09/_09pdelaf/7th/science/webpages/skeleton.html
Classification of Bones
• Classified based on shape and corresponding function
• Four categories– Long bones– Short bones– Irregular bones– Flat bones
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General Features of Bones • Epiphysis
– Ends of the bone– Composed of cancellous (spongy) bone
• Diaphysis– Shaft of the bone– Composed of compact bone
• Medullary cavity– Contains yellow bone marrow
– Epiphyiseal plate
http://pathologyoutlines.com/bone.html
Histology• Four main types of bone cells
– Osteogenic (osteoprogenitor) cells• give rise to osteoblasts , osteocytes
– Osteoblasts• Bone-forming cells• Found along endosteum and
periosteum• Secrete osteocalcin
– Osteocytes• Former osteoblasts that have been
trapped in their lacunae• Maintain bony matrix• Strain sensors
– Octeoclasts• Bone-dissolving cells
• Matrix– composed of inorganic and
organic components
• Inorganic component– Hydroxyapaptite
• Composed mainly of CaPO4 salt
• Organic components – Protein and carbohydrate
• Collagen
• Bone is a composite
Compact Bone• Osteon (haversian system)
– Basic structural unit of compact bone
• Central (haversian) canal surrounded by concentric lamellae (matrix)
• Perforating canals– Transverse or diagonal passages
into the central canal– Originate at nutrient foramen
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Spongy Bone
• Composed by a network of trabeculae
• Spaces filled with red marrow
• Beams arranged to sustain stress
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Bone Development
• Ossification or osteogenesis– Formation of bone
• Two methods– Intramembranous ossification
– Endochondral ossification
Intramembranous Ossification
• Produces flat bones of skull and clavicles
• Starts with osteoid
• End with diploe
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Bone Growth and Remodeling
• Bone Elongation– Involves epiphyseal plates
• Hyaline cartilage between to transitional zones (metaphysis)
• Zones of mataphysis– Reserve cartilage– Cell proliferation– Cell hypertrophy– Calcification– Bone deposition
• Spongy bonenzdl.org
Bone Growth and Remodeling• Interstitial growth
– Result from growth of cartilage within the metaphysis– Finite process
• Epiphyseal line
• Appositional growth– Growth in diameter and thickness
• Circumferential lamellae
• Remodeling– Wolff’s law of bone
• The architecture of bone is determined by the mechanical stresses placed up it.
– Bone adapts to withstand stress
Physiology of Osseous Tissue• Mineral deposition
– Calcium and phosphate are allowed to reach their solubility product
• Precipitate in the matrix– Ectopic ossification
• Abnormal calcification of soft tissue– Calculus
• Mineral resorption– HCl secreted by osteoclasts– Acid phosphatase
• Absorbs collagen
Fractures and Repair
• Fracture– Break in the bone– Two types
• Stress• Pathological• See table 6-2
• Granulation tissue– Fibrous mass of
capillaries and cells within hematoma
medical-definitions.com