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His right elbow appears broken, and part of the bone in the upper arm…

- - - - suspected rickets
- - - - Osteogenic cells
        
        also called osteoprogenitor cells
        
        mitotically active stem cells in endosteum and periosteum
        
        when stimulated, differentiate into different types of bone cells
        
        some remain as osteogenic cells
      - Osteoblasts
        
        bone forming cells that secrete unmineralized bone matrix called osteoid
        
        actively mitotic
      - Osteocytes
        
        amitotic mature bone cells in lacunae
        
        maintain bone strength and act as stress or strain sensors
        
        respond to mechanical stimuli on bone - both positive and negative
        
        communicate information to osteoblasts and osteoclasts so bone remodeling can occur
      - Bone lining cells
        
        flat cells on bone surfaces believed to also help maintain matrix
        
        called periosteal cells on outer surface, endosteal cells on internal surface
      - Osteoclasts
        
        derived from the same hematopoietic stem cells that become macrophages
        
        giant, multinucleate cells that function in bone resorption
        
        when active, located in depressions called resorption bays
        
        cells have ruffled borders that increase surface area for enzyme degradation of bone
        
        also helps seal off area from surrounding matrix
    - - Spongy
        
        made up of a honeycomb of small, needle-like or flat pieces of bone called trabeculae
        
        organized around lines of stress
        
        open spaces are filled with red or yellow bone marrow
        
        red marrow produces red blood cells, platelets, and many white blood cells
        
        yellow marrow produces fat, cartilage, and bone
      - Compact (Lamellar)
        
        dense outer layer on bone that appears smooth and solid
        
        consists of osteon (Haversian system), canals and caniculi, and interstitial and circumferential lamellae
    - - Epiphysis
        
        Location of epiphyseal plate
        
        where bone growth occurs
        
        ends of long bones that consist of compact bone externally and spongy bone internally
        
        articular cartilage covers joint surfaces
      - Diaphysis
        
        tubular shaft that forms long axis of bone
        
        compact bone surrounds medullary cavity that contains yellow marrow in adults
      - Metaphysis
        
        where the epiphysis and diaphysis meet
      - Membranes
        
        Periosteum
        
        white, double layered membrane that covers external surfaces except joints
        
        Osteogenic Layer
        
        inner layer abutting bone and containing primitive osteogenic stem cells that give rise to most bone cells
        
        Fibrous Layer
        
        outer layer consisting of dense irregular connective tissue consisting of Sharpey's fibers that secure bone to matrix
        
        contains many nerve fibers and blood vessels that continue on to the shaft through nutrient foramen openings
        
        anchoring points for tendons and ligaments
        
        Endosteum
        
        delicate connective tissue membrane covering internal bone surface
        
        covers trabeculae of spongy bone tissue
        
        lines canals that pass through compact bone
        
        contains osteogenic cells that can differentiate into other bone cells
  - - - Plate has 5 zones:
        
        Resting zone
        
        area of cartilage on epiphyseal side of plate that is relatively inactive
        
        Proliferation zone
        
        area of cartilage on diaphyseal side is rapidly dividing
        
        Hypertrophic zone
        
        area with older chondrocytes closer to diaphysis; cartilage lacunae enlarge and erode, forming interconnected spaces
        
        Calcification zone
        
        surrounding cartilage matrix calcifies; chondrocytes die and deteriorate
        
        Ossification zone
        
        chondrocyte deterioration leaves spiculesof calcified cartilage at plate junction
        
        spicules are eroded by osteoclasts and covered with new bone by osteoblasts, forming spongy bone
        
        medullary cavity enlarges as spindles are eroded
      - Epiphyseal plate closes at the end of adolescence
        (18 for women, 21 for men)
        
        no more longitudinal growth of bone
  - - - bone forms by replacing hyaline cartilage
      - bones are called cartilage (endochondral) bones
      - form most of skeleton
        
        essentially all bones inferior to the skull except the clavicle
      - Five major steps:
        
        Bone collar forms around diaphysis of cartilage model.
        
        Central cartilage in diaphysis calcifies then develops cavities.
        
        Periosteal bud invades cavities, leading to formation of spongy bone
        
        Diaphysis elongates and medullary cavity forms
        
        Epiphysis ossify.
        
        Hyaline cartilage remains only in epiphyseal plate and articular cartilage
    - - bone develops from fibrous membrane
      - called membrane bones
      - forms frontal, parietal, occipital, temporal, and clavicle bones
      - Four steps involved:
        
        Ossification centers are formed when mesenchymal cells cluster and become osteoblasts.
        
        Osteoid is secreted then calcified.
        
        Woven bone is formed when osteoid is laid down around blood vessels, resulting in trabeculae
        
        outer layer of woven bone forms periosteum
        
        Lamellar bone replaces woven bone and red bone marrow forms.
  - - - function of osteoclasts
      - secrete enzymes and protons that break down matrix
      - acidity converts calcium salts to soluble forms
      - also phagocytize dead osteocytes and demineralized matrix
    - - new bone matrix laid down by osteoblasts
      - osteoid seam: band of unmineralized bone matrix that marks area of new matrix
      - calcification front: abrupt transition zone between osteoid seam and mineralized bone
  - - - torn blood vessels hemorrhage, causing a blood clot called a hematoma to form
      - site is swollen, painful, and inflamed
    - - capillaries grow into hematoma, phagocytic cells clear debris
      - fibroblasts secrete collagen fibers to span break and connect broken ends
      - fibroblasts, cartilage, and osteogenic cells begin reconstruction of bone
    - - new trabeculae appear in fibrocartilagenous callus
      - callus is converted to spongy bone
    - - excess material on diaphysis exterior and within medullary cavity is removed
      - compound bone laid down to reconstruct shaft walls
      - final structure resembles original structure
  - - - includes bone cells and osteoid
      - resilience of bone is due to sacrificial bonds in/between collagen molecules that stretch/break to dissipate energy and prevent fractures
        
        if no additional trauma, bonds reform
    - - Hydroxyapatites (mineral salts)
      - make up 65% of bone composition
      - consists mainly of calcium phosphate crystals between collagen fibers
      - responsible for hardness and resistance to compression
  - - - Displaced or non displaced
        
        Displaced: ends are out of normal alignment
        
        Nondisplaced: ends retain normal position
      - Complete or incomplete
        
        Complete: broken all the way through
        
        Incomplete: not broken all the way through
      - Compound (open) or simple (closed)
        
        Compound: skin is penetrated
        
        Simple: skin is not penetrated
    - - Comminuted: bone broken into three or more fragments
      - Compression: bone is crushed
      - Spiral: ragged break occurs due to twisting forces
      - Epiphyseal: epihysis separates from the diaphysis at the epiphyseal plate
      - Depressed: broken bone is pressed inward
      - Greenstick: bone breaks incompletely, like a green twig; only one side breaks, the other bends
- - - - Surgery
        
        closed reduction
      - Antibiotics
        
        risk of cellulitis and osteomyelitis
      - Immobilization of joint/bone
      - Physical therapy
  - - - requires traction