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THE SKELETAL SYSTEM

This article provides an overview of the structure and function of bones in the skeletal system. It covers topics such as bone types, parts of a bone, mature bone histology, bone growth and development, bone maintenance and repair, and calcium homeostasis.

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THE SKELETAL SYSTEM

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  1. THE SKELETAL SYSTEM

  2. I. BONE STRUCTURE & FUNCTION • FUNCTION • Support • Protection • Movement • Blood formation • Electrolyte Balance • Acid Base Balance

  3. I. BONE STRUCTURE & FUNCTION • Structure • Shape • Long bones • Short bones • Flat bones • Irregular bones

  4. Long bones Short bones

  5. Flat bones Irregular bones

  6. Classify the bone types to the left

  7. B. Structure 2. Parts of Bone • Epiphyses • Contains red bone marrow • Spongy bone and compact bone

  8. Structure • Parts of Bone • Diaphysis • Shaft of bone • Contains yellow bone marrow (stores fat) • Spongy and compact bone

  9. Structure • Parts of Bone • Periosteum • Epiphyseal plate • Allows for growth in bone • Found only in children

  10. B. Structure • Mature Bone Osseous Tissue

  11. 3. Mature Bone • Called Lamellar bone • Two kinds • Compact • Spongy (cancellous)

  12. 3. Mature Bone • Spongy (cancellous) • contains trabeculae • contains spaces

  13. 3. Mature Bone Compact Bone • Dense, few spaces • Haversian canals • Concentric Lamellae

  14. I. BONE STRUCTURE & FUNCTION • Background minerals • Histology • Matrix

  15. C. Histology • Bone cells

  16. Osteoblasts

  17. Osteocytes Osteoclasts

  18. Osteoclasts Osteocytes Osteoblasts

  19. Name C, D & E C = Osteoclast D = Osteoblast E = Osteocytes

  20. D. Membranes • Periosteum: • The external covering of bone

  21. D. Membranes • endosteum: • Found on internal bone surface • covers trabeculae of spongy bone • in marrow cavities

  22. II. BONE GROWTH & DEVELOPMENT • Intramembranous bones • originate between sheet-like layers of connective tissues • Two Patterns of Bone Formation

  23. II. BONE GROWTH & DEVELOPMENT • Endochondral bones • begin as masses of hyaline cartilage that bone tissue later replaces. • Two Patterns of Bone Formation

  24. II. BONE GROWTH & DEVELOPMENT • grow by interstitial growth at epiphyseal plates • rate of cartilage growth is balanced by replacement with bone • end of growth as cartilage cells slow down division • Growth in Long Bones

  25. II. BONE GROWTH & DEVELOPMENT • 2. bones grow in width by appositional growth • Osteoblasts in periosteum: secretes bone matrix • Osteoclasts in endosteum: removes bone matrix (a little slower) • Growth in Long Bones

  26. Appositional Growth • New bone forms at ridges around blood vessels • Periosteum becomes endosteum

  27. Appositional Growth • New lamella formed • More bone added forming osteon

  28. II. BONE GROWTH & DEVELOPMENT • 1. growth hormone from pituitary: stimulates growth in childhood • Gigantism: excessive growth hormone • dwarfism: not enough growth hormone or thyroid hormones • Hormones

  29. II. BONE GROWTH & DEVELOPMENT 2. thyroid: regulates activity of growth hormone 3. sex hormones: promote growth spurt, induce epiphyseal plate closure estrogen: maintains bone density • Hormones

  30. III. Bone Maintenance & Repair • Life long process • 2. Local areas of boneare destroyed and rebuilt • 3. Repairs microdamage caused by normal wear and tear • Bone remodeling:

  31. 1. Simple bone breaks cleanly, does not break through skin • Fractures

  32. 2. Compound broken ends protrude through the skin, risk of bone infection • Fractures

  33. 3. Greenstick Does not break completely • Fractures Greenstick: (children)

  34. III. Remodeling and Repair C. Repair 2. Spongy bone forms in area of hematoma 1.Hematoma forms

  35. C. Repair 4. Remodeling 3.Osteoblasts lay down new bone matrix

  36. III. Calcium Homeostasis • Has a very narrow range • Ca2+Required for • For normal muscle contraction • Nerve impulses • Blood Ca2+ Level

  37. III. Calcium Homeostasis • Abnormal levels • Hypocalcemia • causes marked jitteriness and convulsive seizures • Blood Ca2+ Level

  38. III. Calcium Homeostasis • Abnormal levels • Hypercalcemia • the most common life-threatening metabolic disorder associated with cancer • Blood Ca2+ Level

  39. III. Calcium Homeostasis • Major storage site for calcium • Calcium moves • Into bone as osteoblasts build new bone • Out of bone as osteoclasts break down bone • Bone’s Role

  40. III. Calcium Homeostasis • Parathyroid Hormone – Increases blood Ca2+ levels • Bone, Calcium and Hormones • Calcitonin • Decreases blood Ca2+ levels

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