2.6 Anatomy Chapter 6

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susaneers
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36788
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2.6 Anatomy Chapter 6
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2010-09-25 17:41:57
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Bones Skeletal Tissue
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Bone/Cartilage Characteristics
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  1. The Skeletal System.
    Function
    Characteristics
    • Function:
    • 1. provide support and shape to the body
    • 2. provide attachment sites for muscle (impt for movement)
    • 3. protection
    • 4. acts as a storage depot for essential minerals ( Calcium and phosphate)
    • 5. blood-cell formation, fat storage (red/yellow marrow)
    • [6. Energy metabolism: osteoblasts secrete hormones related to blood sugar)

    • Characteristics:
    • 1. composed of bones, cartilages, and joints
  2. Hyaline Cartilage
    Characteristics
    Location in skeletal system
    • Characteristics:
    • 1. Most abundant
    • 2. Chondrocytes appear spherical
    • 3. Made of collagen fibers
    • 4. Resists compression well (bc of large amts of water)
    • 5. Provides support through flexibility and resilience

    • Location:
    • 1. articular cartilage
    • 2. cartilage attaching ribs to sternum
    • 3. most cartilage in respiratory structures
    • 4. forms embryonic skeleton
  3. Elastic Cartilage
    Characteristics
    Location
    • Characteristics:
    • 1. similar to hyaline, but matrix has elastic fibers as well as collagen
    • 2. more elastic, more tolerant to repeated bending

    • Location:
    • 1. Epiglottis
    • 2. External Ear
  4. Fibrocartilage:
    Characteristics
    Location
    • Characteristics:
    • 1. resists both strong compression and strong tension
    • 2. consists of thick collagen fibers surrounding chondrocytes in lacunae

    • Location:
    • 1. anulus fibrosis portion of vertebral discs
    • 2. articular discs of joints, ex. Knees
    • 3. pubic symphysis
  5. Growth of Cartilage:
    Appositional growth: "from outside"; chondroblasts in perichondrium actively secrete matrix

    Interstitial growth: "from within"; chondrocytes within the cartilage divide and secrete new matrix

    cartilage stops growing in late teens, and cells do not divide again
  6. Extracellular Bone Matrix Composition
    • 35% organic components (collagen)
    • - contribute flexibility and tensile strength
    • - baking at high temperature destroys organic portion

    • 65% inorganic hydroxyapatites (mineral salts: calcium phosphate)
    • - provide exceptional hardness to resist compression, endurance
    • - soaking in acid dissolves mineral salts
  7. Bone Cell Types
    • 1. Osteogenic cells: stem cells that differentiate into bone-forming osteoblasts
    • 2. OsteoBlasts: cells that actively produce and secrete organic components of bone matrix
    • 3. Osteoid: bone matrix secreted by osteoblasts (crystallized calcium salts within)
    • 4. Osteocytes: function to keep bone matrix healthy; no longer producing new osteoid
    • 5. OsteoClasts: cells responsible for bone resorption (derived from white blood cells; secrete HCl and lysosomal enzymes)
  8. Bone Classification:
    1. Long Bones
    2. Short Bones
    3. Flat Bones
    4. Irregular Bones
    • 1. Long bones: longer than they are wide; consists of a shaft and two ends
    • most bones in limbs: humerus, femur, tibia, fibula, ulna, radius, phalanges, metacarpals
    • 2. Short bones: typically cube-shaped; sesamoid bone: "sesame seed-shaped"
    • occur in wrist and ankle: tarsals, carpals; coccyx, patella
    • 3. Flat bones: thin, flattened, usually curved
    • most cranial bones, ribs, sternum, scapula, clavicle
    • 4. Irregular bones: anything that doesn't fit into the previous categories
    • vertebrae, coxal, mandible, sacrum
  9. Gross Anatomy of Bones
    • Diaphysis/ epiphyses
    • Articular cartilage
    • Periosteum: two sublayers: superficial layer of dense irregular connective tissue (resists tension), deep layer consisting of osteoblasts and osteoclasts (bone remodeling)
    • Endosteum: covers internal bone surfaces (also osteogenic)
    • Perforating (Sharpey's) fibers: bundles of collagen that connect periosteum to bone matrix
  10. Bone Markings:
    Sites of Muscle and Ligament Attachment
    Tuberosity, Crest, Trochanter, Line, Tubercle, Epicondyle, Spine, Process

    Surfaces that form Joints
    Head, Facet, Condyle

    Depressions/ Openings
    (for vessels and nerves)
    Foramen, Groove, Fissure, Notch
    (others)
    Fossa, Meatus, Sinus
    • Sites of Muscle and Ligament Attachment
    • 1. Tuberosity - Large rounded projection; roughened
    • 2. Crest - Narrow ridge of bone; usually prominent
    • 3. Trochanter - Large, blunt, irregularly shaped process (only on femur)
    • 4. Line - Narrow ridge of bone; less prominent than crest
    • 5. Tubercle - Small, rounded projection or process
    • 6. Epicondyle - Raised area on or above a condyle
    • 7. Spine - Sharp, slender, often pointed projection
    • 8. Process - Any bony prominence

    • Surfaces that form Joints
    • 1. Head - bony expansion carried on a narrow neck
    • 2. Facet - smooth, nearly flat articular surface
    • 3. Condyle - rounded articular projection, often articulating with a fossa

    • Depressions/ Openings
    • (for vessels and nerves)
    • 1. Foramen - round/oval opening through a bone
    • 2. Groove - Furrow
    • 3. Fissure - Narrow, slit-like opening
    • 4. Notch - Indentation at the edge of a structure
    • (others)
    • 5. Fossa - Shallow, basin-like depression, often an articular surface
    • 6. Meatus - Canal-like passageway
    • 7. Sinus - Cavity within a bone, filled with air and lined with mucous membrane
  11. Microscopic Structure of Compact Bone
    • Central (Haversian) Canal: carries blood vessels, nerves, lymphatic vessels
    • Osteocyte: mature bone cells in Lacunae: chambers
    • Concentric Lamellae: circular tubes surrounding a central canal like rings in a tree trunk
    • Interstitial Lamellae: incomplete remnants of Circumferential Lamellae: at internal and external layer of compact bone
    • Osteon: central canal and all concentric lamellae surrounding it
    • Canaliculi: tiny canals going outward from central canal to lacunae; provides connecting network for nutrient supply
    • Perforating (Volkmann's) Canals: run perpendicular to central canal, from periosteum to bone interior
  12. Bone Development and Growth
    Intramembranous Ossification
    • Membrane bones form directly from mesenchyme without cartilaginous model
    • - All bones in skull except base, and clavicles
    • Week 8 of embryonic development: mesenchymal cells cluster and become osteoblasts that secrete organic bone matrix that become mineralized --> become osteocytes
    • New bone tissue forms btwn blood vessels that result in woven bone tissue, mesenchyme condenses externally and becomes periosteum.
    • Trabeculae at periphery thicken and form compact bone, sandwiching an internal spongy bone.
  13. Bone Development and Growth
    Endochondral Ossification
    • All bones from the base of the skull down, except clavicles
    • - first modeled in hyaline cartilage, gradually replaced by bone
    • - begins late in second month of development, not complete until early adulthood
    • - increases in length and width

    • 1. Bone collar forms around diaphysis
    • 2. Cartilage calcifies in center of diaphysis
    • 3. Periosteal bud (blood vessel) invades internal cavity, forming spongy bone (primary ossification center)
    • 4. Diphysis elongates, medullary cavity forms; secondary ossification centers appear in epiphyses
    • 5. Epiphyses ossify; cartilaginous epiphyseal plates form (hylaine cartilage only in epiphyseal plate and articular cartilages)
  14. Anatomy of Epiphyseal Plate
    • Resting Zone: cartilage cells nearest epiphysis; small and inactive
    • Proliferation Zone: cartilage cells forming tall stacks, top cells divide quickly, pushing epiphyseal plate further away, lengthening bone
    • Hypertrophic Zone: older chondrocytes enlarge and signal matrix to calcify
    • Calcification Zone: matrix becomes calcified, chondrocytes die, leaving trabeculae
    • Ossification Zone: trabeculae covered with bone tissue by osteoblasts
  15. Repair of Bone Fractures
    • Simple fracture: bone breaks cleanly, does not penetrate the skin
    • Compound fracture: bone breaks in multiple pieces; penetrates skin
    • Closed reduction: bone ends realigned by physician (no surgery required)
    • Open reduction: bones realigned by pins/wires (through surgery)
    • Healing requires 6-8wks for a simple fracture in healthy young adults

    • 1. Hematoma formation (inflammation occurs)
    • 2. Fibrocartilaginous callus formation: new blood vessels form, proliferation of osteoblasts, filling of cavity with soft callus which becomes dense CT containing fibro- and hyaline cartilage.
    • 3. Bony callus formation: Within a week, bone trabeculae form via endochondral ossification and unite the two fragments
    • 4. Bone remodeling occurs: months after repair, bone remodels due to mechanical stresses
  16. Bone Diseases
    Osteoporosis
    Osteomalacia and Rickets
    • Osteoporosis: "bone porous condition"
    • low bone mass and deterioration of microscoopic architecture
    • - bone resorption outpaces bone deposition (osteoclast activity > osteoblast activity)
    • - treated by supplemental calcium and vitamin D

    • Osteomalacia and Rickets: "soft bones"
    • bones are inadequately mineralized (lack of vitamin D and calcium phosphate)
    • - calcification does not occur, bone softens and weakens
    • - epiphyses in children become thickened
    • - cured by drinking vitamin D-fortified milk, or sunlight exposure

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