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Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones Bone Structure Development Bone Homeostasis: Remodeling & Repair Homeostatic Imbalances of Bone Developmental Aspects

Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

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Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones Bone Structure Development Bone Homeostasis: Remodeling & Repair Homeostatic Imbalances of Bone Developmental Aspects. Ch. 6: Bone & Skeletal Tissue Skeletal system includes bone & cartilage - PowerPoint PPT Presentation

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Page 1: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Ch. 6: Bone & Skeletal TissueSkeletal CartilagesClassification of BonesFunctions of BonesBone StructureDevelopmentBone Homeostasis: Remodeling & RepairHomeostatic Imbalances of BoneDevelopmental Aspects

Page 2: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Ch. 6: Bone & Skeletal TissueSkeletal system includes bone & cartilageSkeletal Cartilages

Structure, types, locationsAll types of sk cart have chondros, extracell mtx, fibersHyaline c

most common, flexible, resilient, contain fine collagen fibersArticular, costal, respiratory (vb), nasal (ext nose)

Elastic clike hyaline; more elastic fibers; tolerate repeated bending; epigolttis, ext ear

FibrocartCross between hyal cart (chondros) & dense reg conn tiss (thick coll fibers); high tensile strengthResist high pressure & stretchMenisci in knees, intervert discs

GrowthAppositional; Interstitial

Page 3: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.1

Page 4: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Ch. 6: Bone & Skeletal TissueClassification of Bones

Axial vs appendicularBy shape: long, short, flat, irregular

Functions of BonesSupportProtectionMovementStorage of minerals, growth factors, fatHematopoesis

Forces•Tension•Compression•Bending

Page 5: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.2

Page 6: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Ch. 6: Bone & Skeletal TissueBone Structure

Gross AnatomyBone Markings – See Table 6.1Texture

Compact (lamellar): dense outer layer, naked eye smoothSpongy (cancellous): trabeculae, red or yellow marrow

Typical long bone structureDiaphysis: compact bone collar over marrow-filled medullary cavityEpiphyses: bone ends, compact over spongy, articular (hyaline) cartilage;

epiphyseal line (remnant of epiphyseal plate)Membranes: periosteum, endosteum, osteoblasts/clasts

Short, irregular, flat bone structureCompact over spongy; no marrow cavity

Hematopoetic tissue (red marrow): Trabecular parts of long bones (esp. heads of femur, humerus in adult) &

flat bones

Microscopic AnatomyChemical Composition

Page 7: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Table 6.1

Page 8: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Table 6.1

Page 9: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.3

Page 10: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.3a

Page 11: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.3b

Page 12: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.3c

Page 13: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.5

Page 14: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Ch. 6: Bone & Skeletal TissueBone Structure

Gross AnatomyMicroscopic Anatomy

Cell types: osteogenic, osteoblasts, osteocytes, osteoclastsCompact bone

Microscopic passageways; osteons (Haversian systems)Multiple lamellae per osteon; alternating collagen fiber orient’nCentral canal; osteocytes btn lamellae

Spongy boneTrabeculae align with stress; no osteons

Chemical Composition (skeleton = 14-17% of total adult body weight i.e. ~ 10 kg)

OrganicCells & osteoid (ground substance & collagen fibers)

Inorganic (2/3 of skeleton weight – Trotter & Peterson, J Bone Jt Surg Am 1962)

Hydroxyapatite crystals (mainly calcium phosphate) (40% of hydroxyapatite is Ca; total body Ca ~ 2.5 – 3 kg for normal 70 kg person)

Page 15: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.6

Page 16: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

College or Department name here

Bone architecture(a) macroscopic bone,(b) osteons with circular arrangements of differently oriented collagen fibers. (c) collagen fiber = bundles of collagen fibrils. (d) collagen fibril = staggered arrangement of collagen molecules with embedded mineral crystals (blue). (e) collagen molecule triple helix.Collagen: tensile and bending strength.Hydroxyapatite (calcium phosphate): compressive strength

Reinforced concrete “Rebar” (steel reinforcing bars): tensile

and bending strength. Concrete:compressive strength.

Above: channel.nationalgeographic.com/series/la-hard-hats/all/Photos#tab-Photos/11

Left: www.bnl.gov/nsls2/sciOps/chemSci/softMatter.asp

Page 17: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.6

Page 18: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.6a

Page 19: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.6b

Page 20: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.6c

Page 21: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Ch. 6: Bone & Skeletal TissueDevelopment

Ossification (= osteogenesis)

Forming the bony skeletonIntramembranous ossifEndochondral ossif

Postnatal bone growthLength of long bones: epiphyseal plateHormonal regulation

GH. Sex hormones: growth spurt, epi plate closure

Page 22: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.8.

Page 23: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.8

Page 24: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.9

Page 25: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.10

Page 26: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.11

Page 27: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.15

Page 28: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Ch. 6: Bone & Skeletal TissueBone Homeostasis: Remodeling & Repair

RemodelingAt periosteum & endosteumRemodeling unit w/ osteoblasts, osteoclastsOsteocytes (stimulated by osteoblasts) secrete matrixControl of remodeling

By hormones to regulate plasma [Ca]PTH ↑when [Ca] ↓, stimulates osteoclasts

In response to mechanical stressBone strongest where stress acts

Long bone hollow ctr; shaft thickest at middleCurved bones thickest where most likely to breakSpongy bone trabeculae line up along stress linesProjections (tuberosity, crest,…) where muscles attach

Page 29: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Ch. 6: Bone & Skeletal TissueBone Homeostasis: Remodeling & Repair

Remodeling animation with description of osteoporosis (54 s):http://www.youtube.com/watch?v=5uAXX5GvGrI

Page 30: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.12

Page 31: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.13

Page 32: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Ch. 6: Bone & Skeletal TissueBone Homeostasis: Remodeling & Repair

RepairClassification of fractures

Bone end positions: displaced or nondisplacedComplete or incompleteOrientation: linear (long axis) or transverseSkin penetration: open (compund) or closed (simple)By nature, location of break – see Table 6.2

Repair process – see Fig 6.15

Page 33: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Table 6.2

Page 34: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Table 6.2

Page 35: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Radiograph Showing a Subtrochanteric Stress Fracture. Kwek et al., NEJM 359:316, 2008.

Not the most common site for stress fracture. Common stress fracture sites: tibia (runners), metatarsals (dancers, skaters), fibula…) From article about possible increase in fracture risk in patients on bisphosphonates (osteoporosis drugs). See also JAMA 305: 783-789, 2011.Some data suggests that the risk of rare fractures is a lot higher after 6-8 years on bisphosphonates than after 2 yrs; some suggest a bisphosphonate holiday after 5 yrs (NYT 2011-03-06).

A current debate: Do some osteoporosis drugs increase the rate of “rare” fractures?

Page 36: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.15

Page 37: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Ch. 6: Bone & Skeletal TissueHomeostatic Imbalances of Bone

OsteomalachiaFailure to mineralize; weak bonesRickets in childrenDue to Ca deficiency, maybe secondary to vit D deficiency

OsteoporosisResorption > formation; ↓ bone density, massElderly susceptible; vertebral, femoral neck fxEstrogen, testosterone slow osteoclasts, stimulate blastsPost-menopausal fall in estrogenRemodeling animation with description of osteoporosis (41 s):http://www.youtube.com/watch?v=NKVKNqIOnh0&feature=related

Paget’s diseaseDisorganized (Pagetic) bone; spongy/compact too highElderly susceptible; affected bone weak

Page 38: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Figure 6.16

Page 39: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Hip Fractures

• 300,000 hip fractures annually in US• Majority related to osteoporosis and falls in older people• Enormous public health implications and economic burden• A top cause of immobilization in elderly• Patients who have sustained a hip fracture

• 2-year mortality rate of 36%

• Immobility → increased bone resorption, predisposition to 2nd hip fracture

• Many don’t regain prefracture level of mobility; lose independence, QOL

• Risk of subsequent skeletal fracture up 2.5x

• Risk of new hip fracture up 5x – 10x

Editorial: Calis KA, Pucino F, NEJM 2007: Sep 17, epub ahead of print

Page 40: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

College or Department name here

Drug therapy for osteoporosisCa, Vitamin D supplementationBisphosphonates

Many have names ending in –dronateFosamax/alendronate, Actonel/risedronate, etc.

Reduce activity of osteoclastsReduce bone remodelingSide effects: osteonecrosis of jaw, uncommon fractures, etc.

PTH analogsForteo/teriparatide34 aa fragment of PTH (84 aa)Mechanism of action mysterious

Page 41: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Further reading:

NYTimes Sep 23 2009Can vitamin D improve athletic performance?http://well.blogs.nytimes.com/2009/09/23/phys-ed-can-vitamin-d-improve-your-athletic-performance/

Vitamin D essential for absorption of Ca from gut; it also helps other cells including muscle cells use Ca. Many of us with a “normal” diet and occasional outdoor time are vitamin D deficient and we may benefit from more D.

Vitamin D Status and Its Relation to Muscle Mass and Muscle Fat in Young Women. 59% of sample (16-22 yo ♀ in Calif) had insufficient 25OH-D (<30 ng/ml), including 24% who were deficient in 25OH-D (<20 ng/ml) (surprisingly large %). Vitamin D insufficiency was associated with increased fat infiltration in muscle. Gilsanz, …, Kremer. J Clin Endocrinol Metab 2010; DOI: 10.1210/jc.2009-2309

Page 42: Ch. 6: Bone & Skeletal Tissue Skeletal Cartilages Classification of Bones Functions of Bones

Further reading:

NY Times Sep 1 2009Does ibuprofen help or hurt during exercise?http://well.blogs.nytimes.com/2009/09/01/phys-ed-does-ibuprofen-help-or-hurt-during-exercise/

Many athletes regularly take ibuprofen. Article describes increasing evidence that "vitamin I" has negative side effects including blunted growth response of bone to applied stress, decreased post-workout collagen production, etc. One scientist wrote recently in Brit J Sports Med that regular ibuprofen use around the time of exercise diminishes the expected increase in skeletal strength that otherwise comes from exercise. http://bjsm.bmj.com/cgi/content/full/43/8/548