Anatomy ch 6

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cswett
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38620
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Anatomy ch 6
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2010-10-04 23:05:03
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Anatomy Bone Homeostasis
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Anatomy, Bone structure
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  1. Functions of Skeletal System
    • 1. Support
    • 2. Protection
    • 3. Assistance in Movement
    • 4. Mineral homeostasis
    • 5. Blood cell production (Red bone marrow)
    • 6. Triglyceride storage (yellow bone marrow)
  2. hemopoiesis
    red bone marrow producing red blood cells, white blood cells, and platelets
  3. diaphysis (is - single)
    • bone's shaft or body
  4. epiphyses (es- plural)
    distal and proximal ends of the bone
  5. metaphyses
    regions in the mature bone where the diaphysis joins the epiphyses
  6. epiphyseal plate
    part of the metaphysis - a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length
  7. epiphyseal line
    in a mature bone the cartilage of the epipyseal plate is replaced by bone
  8. Articular cartilage
    thin layer of hyaline cartilage covering the part of the eipihysis where the bone forms an articulation (joint) with another bone
  9. periosteum
    • tough sheath of dense irregular CT that surround the bone surface wherever it is not covered by articular cartilage
    • bone-forming cells of periosteum enable bone to grow in thickness but not length
    • protect the bone, assists in fracture repair, helps nourish bone tissue, and serves as attachment point for ligaments and tendons
  10. perforating (Sharpey's) fibers
    thick bundles of collagen fibers that extend from the periosteum into the extracellular bone matrix (attaches periosteum to bone)
  11. medullary cavity
    marrow cavity - space within the diaphysis that contains fatty yellow bone marrow in adults
  12. endosteum
    • thin membrane that lines the medullary cavity
    • contains single layer of bone-forming cells and a small amount of CT
  13. calcification
    • mineralization - minerals form crystals in presence of collagen fibers
    • crystals laid over collagen fibers
    • crystals - hardness
    • collagen fibers - tensile strength
  14. tensile strength
    resistance to being stretched or torn apart
  15. Four types of bone cells
    • 1. Osteogenic cells
    • 2. Osteoblasts
    • 3. Osteocytes
    • 4. Osteoclasts
  16. Osteogenic cells
    • stem cells (from mesenchymal cells)
    • only bone cells to undergo cell division - produces osteoblasts
    • located in the periosteum, endosteum, and in bony canals with blood vessels
  17. osteoblasts
    • produce new bone matrix
    • when they are completely surrounded by bone matrix, osteoblasts transform into osteocytes
  18. osteocytes
    • mature bone cells located in lacunae (little lake)
    • maintain the bone tissue
  19. osteoclasts
    ruffled border
    • break down bone - resorption
    • large, multinucleated cells - numerous monocytes joined
    • located in endosteum
    • ruffled border - plasma membrane is deeply folded - contains powerful lysosomal enzymes and acids to break down bone matrix
  20. resorption
    • performed by osteoclasts
    • breakdown bone extracellular matrix - part of normal bone development, growth, maintenance, and repair
  21. compact bone
    • contains few spaces - dense
    • form superficial part of bones (right below periostium)
    • 80% of all bones in body
    • basic unit is an osteon
  22. osteon - Haversian system
    • 1. Volkmann's canals (Perforating canals) - run perpendicular to bone surface - house blood vessels, lymphatic vessels, & nerves
    • 2. Central canal - parallel to bone surface (center of osteon) - surrounded by concentric lamellae
    • 3. Concentric lamellae - rings of bony matrix
    • 4. Lacunae - little lake - openings between concentric lamellae that house osteocytes
    • 5. Canaliculi - tiny canals through which osteocyte extensions form different lacunae connect to each other and to the central canal
  23. interstitial lamella
    • located in spaces between osteons
    • remnants of broken down osteons
  24. circumferential lamellae
    lamellae that encircles the bone just beneath the periosteum or encircle the medullary cavity
  25. spongy bone
    trabeculae
    • Trabeculae - loose network of thin beams
    • contain lacunae with osteocytes and canaliculi - no osteons
    • make up most of short, fat and irregular bone (deep part- surface is compact bone)
    • found in long bones in the epiphyses and around medullary cavity
    • reduced weight of skeleton
    • able to withstand stress form many directions
    • protect and support red bone marrow - site of hemopoiesis (blood production)
  26. Blood supply to long bones
    4 types of arteries:
    • 1. Periostial arteries - supply periosteum and superficial part of diaphysis
    • 2. Nutrient arteries - enter through nutrient foramen and sends proximal and distal branches out (supplies deeper part of diaphysis and medullary cavity
    • 3. Metaphyseal arteries - supply red bone marrow and metaphyses
    • 4. Epiphyseal arteries - supply epiphyses
  27. ossification or osteogenesis
    types of ossification
    • process of bone formation
    • 1. embryonic skeleton - template of CT and hyaline cartilage
    • 2. ossification of template occurs - 6th or 7th week of embryonic development in one of two ways:

    • A. Intramembranous ossification
    • B. endochondral ossification
  28. Intramembranous ossification
    4 steps
    • bone building within membranes -bone forms in or on CT membranes
    • results in flat bones
    • 1. Ossification centers develop where osteoblasts are actively producing matrix
    • 2. Osteocytes form and matrix calcifies with the arrival of minerals
    • 3. Trabeculae develop and form spongy bone
    • 4. Periosteum develops and compact bone replaces spongy bone at the surface
  29. Endochondral ossification
    • within cartilage - hyaline cartilage template becomes ossified
    • results in most bones
    • 1. Development of cartilage model from mesenchymal cells - chondrocytes produce hyaline model surrounded by perichondrium (turns to perichondrium when produces bone)
    • 2. Growth of cartilage model in length and width - chondrocytes enlarge and burst - release acids to foster calcification - other chondrocytes die leaving empty spaces (lacunae)
    • 3. Development of primary ossification centers -a region where bone tissue replaces cartilage - osteoblasts lay down spongy bone - Osteoblasts develop in deep regions of periochondreum and produce the Periosteal Bone Collar
    • 4. Development of medullary cavity - osteoclasts break down newly formed spongy bone leaving cavity in shaft
    • 5. Development of secondary ossification center - branches of epiphyseal arteries grow into epiphyses and stimulates ossification
    • 6. Formation of articular cartilage and epiphyseal plates - remnants of hyaline cartilage become articulating (joint) cartilage - hyaline cartilage remnents between diphysis and epiphyses form epiphyseal plate
  30. interstitial growth
    appositional growth
    • interstitial growth - growth from within - increase in length
    • appositional growth - increase in thickness - addition of extracellular matrix material to the periphery by new chondroblasts that develop from the perichondrium
  31. Epiphyseal plate
    4 zones of growth plate
    • layer of hyaline cartilage in the metaphysis of a growing bone
    • Zones:
    • 1. Zone of resting cartilage - layer nearest the epiphysis
    • 2. Zone of proliferating cartilage - large chondrocytes undergo interstitial growth as they divide and secrete extracellular matrix
    • 3. Zone of calcified cartilage - extracellular matrix calcifies and adds to diaphysis
  32. bone remodeling
    bone resorption
    bone deposition
    • bone remodeling -ongoing replacement of old bone tissue by new bone tissue
    • bone resorption - removal of minerals and collagen fibers from bone by osteoclasts
    • bone deposition - addition of minerals and collagen fibers to bone by osteoblasts
  33. Fracture
    8 types of fracture
    • Fracture - any break in any bone
    • 1. Open (Compound fracture) - protrudes through skin
    • 2. Closed (simple) fracture - not protrude through skin
    • 3. Comminuted fracture - bone splinters and produces fragments
    • 4. Greenstick fracture - shaft is not completely broken (only in children - nones not fully ossified)
    • 5. Impacted fracture - one broken end driven inside other broken end
    • 6. Pott's fracture - at ankle - both tibia and fibula are involved
    • 7. Colles' fracture - distal end of radius is displaced posteriorly
    • 8. Stress fracture - minute tears - commonly tibia - due to exercise or osteoporosis
  34. Steps in repair of bone fracture:
    • 1. Formation of fracture hematoma - blood leaking from torn vessels clot around the fracture (6 to 8 hours) blood stops - nearby bone tissue dies - phagocytes and osterclasts remove damaged tissue (several weeks)
    • 2. Fibrocartilaginous callus formation - a mass of repair tissue consisting of collagen fibers and cartilage that bridges the broken ends of the bone (3 weeks)
    • 3. Bony callus formation - fibrocartilage is converted into spongy bone (called bony callus lasts 3 to 4 months)
    • 4. Bone remodeling - bone remodeling of callus - spongy bone turned into compact bone around periphery.
  35. parathyroid hormone (PTH)
    • secreted by parathyroid gland
    • hormone that increses the blood calcium level (negative feedback system)
  36. calcitriol
    hormone that promotes absorption of calcium from foods in the gastrointestional tract into the blood
  37. demineralization
    the loss of calcium and other minerals from bone extracellular matrix
  38. Axial skeleton
    bones that lie around the longitudinal axis of the human body - skull, ribs, sternum, vertebral column
  39. appendicular skeleton
    bones of upper and lower limbs plus the girdles that connect the limbs to the axial skeleton
  40. long bones
    • greater length than width
    • consist of a shaft and variable number of extremities
    • are curved for strength
    • consist of mostly compact bone in diaphysis with spongy bone in epephises
  41. short bone
    • somewhat cube-shaped and are nearly equal in length and width
    • spongy bone except at surface - thin layer of compact bone
    • carpals, tarsals
  42. flat bone
    thin and composed of two parallel layers of compact bone enclosing a layer of spongy bone

    cranial bones, ribs
  43. sesamoid bone
    • shaped like a sesame seed
    • develop in certain tendons where there is considerable friction, tension, and physical stress

    patella
  44. irregular bones
    complex shapes - cant be grouped elsewhere - very in amount of compact and spongy bone

    • vertebra
    • hip bones
    • facial bones
  45. sutural bone (wormian bone)
    small bones located in sutures between cranial bones

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