BONE Clavicle Fracture by mikesanye

VIEWS: 145 PAGES: 40

									                          BONE
•   206 bones in adult
    – 270 bones at birth
•   organization
    – axial skeleton- 80 bones
        • skull- 29 bones
        • vertebral column- 26 bones
        • thorax (ribs and sternum)- 25 bones
    – appendicular skeleton- 126 bones
        • pectoral girdle- 4 bones
        • upper limbs- 60 bones
        • pelvic girdle- 2 bones
        • lower limbs- 60 bones
              BONE FUNCTIONS

• support - attaches to most skeletal muscles
• movement - needs articulations
• protection - brain, heart, lungs, blood forming tissue,
  bladder
• mineral reserve - Ca, P, Na, K
• blood cell production
   – red marrow
• storage of energy
   – yellow marrow
             BONE FUNCTIONS

• acid-base balance
   – absorb or release alkaline salts
• detoxification
   – removes heavy metals and other foreign elements
     from the blood
                 Bone Problem


• Ann is a 55 year old white woman who is postmenopausal
  and who has done little exercise in her life
• Ann has experienced a fracture of the hip and is concerned
  about possible osteoporosis
• Ann does not understand the cause or treatment of
  osteoporosis
   – she decided to have a bone density test
                BONE TYPES

1. Compact or dense bone
2. Spongy or cancellous bone
 EXTERNAL ANATOMY OF LONG BONE

• diaphysis -- shaft
• epiphysis with proximal and distal ends
• medullary or marrow cavity
   – center of ________________
   – fat storage- yellow marrow
      • gelatinous bone marrow -- reddish jelly that replaces
        yellow marrow in old age
• endosteum
   – thin layer
   – lines ___________ cavity
   – dense irregular connective tissue
   – contains _______________ cells
 EXTERNAL ANATOMY OF LONG BONE

• periosteum
   – double layer of dense irregular connective tissue
       • outer fibrous layer
       • inner osteogenic layer
   – elastic fibers, blood vessels, bone cells
   – lines outside of bone
• sharpey’s fibers
   – ______________ fibers that penetrate into bone matrix
• no periosteum at ends- ___________ cartilage
 EXTERNAL ANATOMY OF LONG BONE

• Compact bone
   – outer surface of bone
• Spongy bone or _________________
   – central regions of flat bone
   – within epiphyses of long bones
   – reduces weight of bone
   – forms along lines of stress
   – contains _________ marrow
           RED BONE MARROW

• Major areas:
  – Ribs
  – Sternum
  – Vertebrae
  – Innominate bones
  – Head of femur
  – Head of humerus
     HISTOLOGY OF COMPACT BONE

• Haversian systems or osteons
   – Haverisan canals - contains blood vessels & nerves
   – Volkmann's canals - perpendicular to HC
      • connect HC to outside blood vessels
          – 1/2 liter of blood per minute
   – lamellae - ring of hard calcified intercellular substance
       • concentric
       • interstitial
       • circumferential
   – lacunae - spaces that contain _______________
   – canaliculi - connect osteocytes
       • connected by __________ junctions
             CELLS IN BONE

a. osteogenic cells
  - found in cellular layer of periosteum,
      endosteum and Haversian canals
  - ________ cells --> osteoblasts
                  CELLS IN BONE

b. osteoblasts
   - produce bone matrix
   - before calcium salts are
   deposited -- __________
   - promotes deposition of
   calcium in the matrix
   - osteoblasts become
   surrounded by bone and
   are
   now called ___________
   - not mitotic
OSTEOBLAST FORMING BONE
                    CELLS IN BONE

c. Osteocytes
   - cannot divide
   - two functions
          1. maintain and
          monitor protein and
          mineral content of
          matrix
          2. participate in repair
          of damaged bone
   - if released from lacunae
   can form ___________ or
   ______________cells
                 CELLS IN BONE

d. osteoclasts in Howship's
   lacunae
   - multinuclear- up to 50
   nuclei
   - derived from
   _____________
   - sends out projections
   toward bone and secrete
        two substances:
        1. ___________
                enzymes
        - acid phosphatase
        - from lysosomes and
        digest collagen
        2. acids- _______ and
        ___________ acids
   HISTOLOGY OF SPONGY BONE

• no haversian systems
• thin plates called
  ____________
• osteocytes in lacunae
   – canaliculi but link to
      surrounding red bone
      marrow
                MATRIX OF BONE

1. inorganic salts- 67%
    – hydroxyapatite- Ca10 (PO4)6(OH)2
    – other salts
    – Mg, Na, K, CO3- not in crystal form
    – strontium, uranium, plutonium, lead, gold
        • 9 of 14 of the major radioactive products from
          hydrogen bomb
    – function
        • allows bone to withstand __________
    – calcination
        • remove organic material by __________
              MATRIX OF BONE

2. organic framework or osteoid -- 33%
    collagenous fibers and chondrin
    function
        provide bone with great _________ strength
        ability to resist stretching and twisting
    acid treatment
       remove inorganic salts with acid
       leaves the protein
                  OSSIFICATION

•    begins 6th week of embryo
•    continues until about age of 25

•    types
    1. Intramembranous ossification
        • flat bones of skull, mandible and clavicle
        • called dermal bones
    2. Endochondral ossification
        • most of the bones in the body
        • formed from hyaline cartilage
  INTRAMEMBRANOUS OSSIFICATION

1. Mesenchyme cells --> osteoblasts --> osteocytes
   – osteoblasts secrete ___________ matrix
      • osteoid becomes mineralized thru
        crystallization of Ca salts -- using enzyme
        __________________
   – called ossification center

2. Blood vessels begin to grow
   – spicules meet and fuse together
  INTRAMEMBRANOUS OSSIFICATION

3. Spongy bone gives rise to compact bone on the
   outside

4. Ossification is incomplete at birth
    dense irregular CT left are called fontanels
    _______________ at birth
    most close by 12 months, all close by 24 months
     ENDOCHONDRAL OSSIFICATION

1. Hyaline cartilage (step 1)
    perichondrium

2. Bony collar (step 2)
    osteoblasts gather on inner surface of
     perichondrium -- begin laying down bone
     called the bony collar
    in the center, cartilage cells enlarging and
     dying
     ENDOCHONDRAL OSSIFICATION

3. Primary ossification center (steps 3 and 4)
   – cartilage cells dying and calcified matrix begins to
      degenerate
   – blood vessels enter matrix carrying:
       • ______________ to form bone
       • ______________ to dissolve bone forming
         marrow cavity
   – 3rd month of fetal life
     ENDOCHONDRAL OSSIFICATION

4. Secondary ossification center (step 5)
   – shortly after birth in the proximal epiphysis, a
     secondary ossification center forms
      • no marrow cavity forms
   – at two years old secondary ossification center
     forms at the distal epiphysis
   – two areas of cartilage left after 2 years old
      a. ___________ cartilage - on ends
      b. ___________ plate - between primary and
          secondary ossification centers
     ENDOCHONDRAL OSSIFICATION

5. End of endochondral ossification (step 6)
    for most bone, stops by ages of ________
    epiphyseal plate ossifies to form the epiphyseal
     line
    articular cartilage only remaining cartilage
       • found at the ends of the bone
     PRIMAR Y OSSIFICATION CENTER
             METAPHYSIS
1.    Zone of reserve cartilage

2.     Zone of cell proliferation
     •   chondrocytes multiply and become arranged into
         longitudinal columns of flattened lacunae

3.     Zone of hypertrophy
     •   chondrocytres cease to divide and hypertrophy
    PRIMAR Y OSSIFICATION CENTER
            METAPHYSIS

•       4. Zone of calcification
    •     minerals (Ca++) are deposited in matrix

•     5. Zone of bone deposition
    •    chondrocytes die
    •    osteoblasts invade and lay down trabeculae
    •    osteoclasts erode bone away and leave marrow
         cavity
    •    osteoblasts continue to lay down compact bone
         on the bony collar
        BONE GROWTH - LENGTH
• on epiphyseal side
   – chondrocytes continually reproduce by _________
• on diaphyseal side
   – chondrocytes swell and become surrounded by
     calcified matrix
   – chondrocytes die, bone replaces chondrocytes
   – bone is eroded away by osteoclasts, marrow cavity
     forms
• epiphyseal plate remains constant ______________
• epiphyseal plate becomes ossified- _____________
   – 18 years in females
   – 20 years in males
     BONE GROWTH - DIAMETER

 compact bone remains constant _____________
 marrow cavity increases in diameter
 balance between osteoblasts and osteoclasts not
      always same
     PIEZOELECTRIC EFFECT

 bone is deposited in proportion to compressional
  load
 compression causes a ________ potential at the
  site
    • remainder of bone has a _________ potential
  REQUIREMENTS FOR BONE GROWTH

1. Salts
    Ca & P
       • calcium is the most abundant mineral in body
          – stores 99% of calcium in bone
          – plasma - Ca++
      • stores 85-90% of P in bone
          – plasma - HPO4-2 and H2PO4-1


    Mg, F, Fe, and Mn
  REQUIREMENTS FOR BONE GROWTH

2. Vitamins
    Vit. A -- stimulates chondroitin sulfate synthesis
    Vit. K and B12 -- synthesis of proteins
    Vit. C -- collagen synthesis and stimulates
      osteoblast differentiation
    Vit. D3 -- forms calcitriol which causes increased
      absorption of Ca and P from intestine
  REQUIREMENTS FOR BONE GROWTH
3. Hormones
     calcitriol -- Ca & P absorption from small intestine
     other hormones:
       Growth hormone
       Thyroid hormones
       Glucocorticoids
       Insulin
     sex hormones (estrogen and testosterone)
       • stimulates osteoblast activity and closure of
         epiphyseal plate
       • Estrogen has a stronger effect so growth starts and
         stops earlier than with testosterone
       • anabolic steroids (testosterone) and prematurely
         close epiphyseal plate
  REQUIREMENTS FOR BONE GROWTH
3. Hormones (continued)
     Parathyroid hormone
       • from parathyroid gland
       • increases blood calcium - 10% fluctuation is normal
           – increase blood Ca by 30% --> neurons and
             muscles are unresponsive
           – decrease blood Ca by 35% --> neurons excite and
             may cause convulsions
       • works on three levels
           a. Bone
               » increases number & activity of osteoclasts
               » decreases activity of osteoblasts
  REQUIREMENTS FOR BONE GROWTH

3. Hormones (continued)
     Parathyroid hormone
       b. Kidney
           • increases reabsorption of Ca
           • increases excretion of P
       c. Intestine
           – activate vitamin D3 to calcitriol
               » cholesterol --> (UV light) --> Vit. D3 -->
                 calcidiol (liver) --> calcitriol (kidney, PTH)
               » increases absorption of Ca and P from
                 intestine
  REQUIREMENTS FOR BONE GROWTH

3. Hormones (continued)
     Parathyroid
       • Hyperparathyroidism
           – _________ PTH
           – depresses nervous system
           – brittle bones, kidney stones
       • Hypoparathyroidism
           – _________ PTH
           – increased excitability of nervous system
           – respiratory paralysis
  REQUIREMENTS FOR BONE GROWTH

3. Hormones (continued)
    Calcitonin
      • from parafollicular cells or C cells of the
        _________
      • decreases blood Ca
      • acts mainly on bone
          – decrease activity of osteoclasts
          – increases activity & number of osteoblasts
      • infants - _____________
      • adults - ______________
          – accounts for movement of 0.8 grams of Ca
            per day
              Problem - Osteoporosis
                    Treatments


   Hormone Replacement Therapy (HRT)
     types
      1. estrogen (ERT)
      2. estrogen + progestin (HRT)
     side effects
       nausea, bloating, breast tenderness, high blood
         pressure and blood clots
       issue of a relationship between breast cancer and
         estrogen use is still to be determined.
               Problem - Osteoporosis
                     Treatments

 Alendronate Sodium and Risedronate Sodium
    biphosphonates (bind to hydroxyapetites)
    reduces bone loss, increased bone density, and reduces
     risk of spine fractures and hip fractures
    side effects rare - abdominal pain, nausea, heartburn,
     irritation of esophagus
 Raloxifene
    selective estrogen receptor modulators (SERMs)
    produces increase in bone mass
    side effects rare - hot flashes and deep vein
     thrombosis
 Calcitonin
    side effect - may cause allergic reaction- flushing of face
     and hands, urinary frequency, nausea and a skin rash
            Problem - Osteoporosis
                  Prevention

 calcium
    1000 - 1300 mg per day
 vitamin D
    fortified dairy products, egg yolks, saltwater
     fish and liver
 exercise
    weight-bearing
 bone mineral tests

								
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