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Bones and Skeletal Tissue. Chapter 6. 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 - PowerPoint PPT Presentation
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Bones and Skeletal Tissue
Chapter 6
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
massasoit-bio.net
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
Structure of Bone
Figure 5.1
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
ask.com
Spongy Bone
• Composed by a network of trabeculae
• Spaces filled with red marrow
• Beams arranged to sustain stress
commons.wikimedia.org
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
massasoit-bio.net
Endochondral Ossification• Bone develops from a hyaline model
trjohn.blogspot.com
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
Bone Disorders• Osteoporosis
– Sever loss of bone density • Osteoclast more active than osteoblasts
• Osteosarcoma– Most common and deadly form of bone cancer
• Metastasizes quickly
• Osteogenesis imperfecta– Brittle bones
• Defect in collagen deposition
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