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BONE

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Title: BONE


1
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

2
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

3
BONE FUNCTIONS
  • acid-base balance
  • absorb or release alkaline salts
  • detoxification
  • removes heavy metals and other foreign elements
    from the blood

4
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

5
BONE TYPES
  • 1. Compact or dense bone
  • 2. Spongy or cancellous bone

6
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

7
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
  • sharpeys fibers
  • ______________ fibers that penetrate into bone
    matrix
  • no periosteum at ends- ___________ cartilage

8
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

9
RED BONE MARROW
  • Major areas
  • Ribs
  • Sternum
  • Vertebrae
  • Innominate bones
  • Head of femur
  • Head of humerus

10
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

11
CELLS IN BONE
  • a. osteogenic cells
  • - found in cellular layer of periosteum,
  • endosteum and Haversian canals
  • - ________ cells --gt osteoblasts

12
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

13
OSTEOBLAST FORMING BONE
14
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

15
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
  • - dissolve bone salts

16
HISTOLOGY OF SPONGY BONE
  • no haversian systems
  • thin plates called ____________
  • osteocytes in lacunae
  • canaliculi but link to surrounding red bone
    marrow

17
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 __________

18
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

19
OSSIFICATION
  • begins 6th week of embryo
  • continues until about age of 25
  • types
  • Intramembranous ossification
  • flat bones of skull, mandible and clavicle
  • called dermal bones
  • Endochondral ossification
  • most of the bones in the body
  • formed from hyaline cartilage

20
INTRAMEMBRANOUS OSSIFICATION
  • 1. Mesenchyme cells --gt osteoblasts --gt
    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

21
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

22
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

23
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

24
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

25
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

26
PRIMARY OSSIFICATION CENTERMETAPHYSIS
  • Zone of reserve cartilage
  • Zone of cell proliferation
  • chondrocytes multiply and become arranged into
    longitudinal columns of flattened lacunae
  • Zone of hypertrophy
  • chondrocytres cease to divide and hypertrophy

27
PRIMARY OSSIFICATION CENTERMETAPHYSIS
  • 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

28
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

29
BONE GROWTH - DIAMETER
  • compact bone remains constant _____________
  • marrow cavity increases in diameter
  • balance between osteoblasts and osteoclasts not
    always same

30
PIEZOELECTRIC EFFECT
  • bone is deposited in proportion to compressional
    load
  • compression causes a ________ potential at the
    site
  • remainder of bone has a _________ potential

31
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

32
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

33
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

34
REQUIREMENTS FOR BONE GROWTH
  • 3. Hormones (continued)
  • Parathyroid hormone
  • from parathyroid gland
  • increases blood calcium - 10 fluctuation is
    normal
  • increase blood Ca by 30 --gt neurons and muscles
    are unresponsive
  • decrease blood Ca by 35 --gt neurons excite and
    may cause convulsions
  • works on three levels
  • a. Bone
  • increases number activity of osteoclasts
  • decreases activity of osteoblasts

35
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 --gt (UV light) --gt Vit. D3 --gt
    calcidiol (liver) --gt calcitriol (kidney, PTH)
  • increases absorption of Ca and P from intestine

36
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

37
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

38
Problem - OsteoporosisTreatments
  • Hormone Replacement Therapy (HRT)
  • types
  • estrogen (ERT)
  • 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.

39
Problem - OsteoporosisTreatments
  • 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

40
Problem - OsteoporosisPrevention
  • 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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