Skeletal System:Skeletal System:Osseous Tissue & Osseous Tissue & Skeletal StructureSkeletal Structure

Chapter 6Chapter 6

28 million Americans have 28 million Americans have OSTEOPOROSISOSTEOPOROSIS

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Skeletal System: IntroSkeletal System: Intro Includes: bones, cartilage, ligaments, & Includes: bones, cartilage, ligaments, &

other connective tissuesother connective tissues Functions:Functions:

1.1. SupportSupport2.2. StorageStorage: :

– Mineral reserve (CaMineral reserve (Ca2+2+ & P ions) & P ions)– Lipid (fat) in yellow marrowLipid (fat) in yellow marrow

3.3. Blood Cell ProductionBlood Cell Production4.4. ProtectionProtection: brain, spinal cord, lungs: brain, spinal cord, lungs5.5. Movement & LeverageMovement & Leverage

Histology of Bone: Matrix & CellsHistology of Bone: Matrix & Cells MatrixMatrix= ground substance & protein fibers= ground substance & protein fibers

– SolidSolid calcium salts (i.e. Calcium Phosphate) calcium salts (i.e. Calcium Phosphate)– Protein fibers: collagen and othersProtein fibers: collagen and others

3 types of cells:3 types of cells:1.1. OsteoblastsOsteoblasts

– Imp. for fracture repairImp. for fracture repair– Osteogenesis-bone birthOsteogenesis-bone birth

2.2. OsteoclastsOsteoclasts: Osteolysis (bone break down) / re-: Osteolysis (bone break down) / re-absorptionabsorption

3.3. OsteocytesOsteocytes– Lay down mineral content of matrixLay down mineral content of matrix– MaturedMatured osteoblasts trapped in bone matrix osteoblasts trapped in bone matrix

Histological DifferencesHistological Differences Compact BoneCompact Bone1.1. OsteonOsteon: basic : basic

unitunit– Central Central

Haversian Haversian CanalCanal

– LacunaeLacunae– OsteocyteOsteocyte– LamellaeLamellae

Calcified Calcified matrix matrix layerslayers

– Canaliculi Canaliculi

Spongy BoneSpongy Bone1.1. No OsteonsNo Osteons

– Lamellae= Lamellae= trabeculaetrabeculae

– Osteocytes in lacuna Osteocytes in lacuna connected by connected by canaliculicanaliculi

2.2. Marrow spaces: inside Marrow spaces: inside spongy bonespongy bone– nutrients & wastes nutrients & wastes

diffusediffuse– Blood cell formationBlood cell formation

Spongy Bone

Compact Bone

Compact Bone= Cortex•Covers spongy bone•Osteons parallel to long axis•Good unidirectional support

Diaphysis= shaft•Compact•Spongy•Marrow

MetaphysisEpiphysis= ends

Spongy Bone= ends & flat bones•Lines marrow & lighter to move•Trabeculae cross-bracing•Good multidirectional support

Articular Cartilage•Joint surfaces

Long Bone Layers ArrangementLong Bone Layers Arrangement PeriosteumPeriosteum

– Fibrous outer layer (dense regular C.T.)Fibrous outer layer (dense regular C.T.)– Binds to joint capsule & tendonsBinds to joint capsule & tendons

Compact BoneCompact Bone Spongy BoneSpongy Bone: trabeculae: trabeculae EndosteumEndosteum

– Covers trabeculae, lines marrow cavityCovers trabeculae, lines marrow cavity– Cells: osteoclasts, osteoblastsCells: osteoclasts, osteoblasts

Medullary CavityMedullary Cavity (AKA marrow cavity) (AKA marrow cavity)– Red marrow in spongy boneRed marrow in spongy bone

Function: Function: Hemopoiesis-Hemopoiesis- blood cell formation blood cell formation– Yellow marrow in marrow cavity: fat storageYellow marrow in marrow cavity: fat storage

Periosteum

Endosteum

Osteoblasts

Osteoclast

Compact Bone

Spongy

Osteocytes

Long Bone StructureLong Bone Structure

Bone: Development & Growth Bone: Development & Growth TermsTerms

Skeletal growth Skeletal growth – Determines size & proportion of Determines size & proportion of

bodybody– Starts 6 wks. after egg fertilization Starts 6 wks. after egg fertilization

until approx. 18-25 years olduntil approx. 18-25 years old

Types of Bone GrowthTypes of Bone Growth Ossification: Ossification:

– Process of replacing other tissues w/ bone Process of replacing other tissues w/ bone Developing New BoneDeveloping New Bone

Increasing Diameter (width) of BoneIncreasing Diameter (width) of Bone1.1. Appositional growthAppositional growth

Lengthening Bones (growing taller)Lengthening Bones (growing taller)1.1. Epiphyseal plate endochondral ossificationEpiphyseal plate endochondral ossification

Appositional GrowthAppositional Growth Increases diameter by forming new Increases diameter by forming new

osteonsosteons

Epiphyseal Plate LengtheningEpiphyseal Plate Lengthening Epiphyseal plate: cartilageEpiphyseal plate: cartilage

Cartilage plate in metaphysis Cartilage plate in metaphysis Grows & divides pushing epiphyses away from Grows & divides pushing epiphyses away from

diaphysisdiaphysis Matrix calcifiesMatrix calcifies chrondrocytes eventually die chrondrocytes eventually die

Osteoblasts replace calcified cartilage with Osteoblasts replace calcified cartilage with bone bone

When bone growth> cartilage growthWhen bone growth> cartilage growth stop stop growing growing epiphyseal plate becomes ossifiedepiphyseal plate becomes ossified epiphyseal line epiphyseal line

InvadingCalcium

Osteoblasts

Chondrocytes: New & Old

Requirements for Normal Bone Requirements for Normal Bone GrowthGrowth

Dietary minerals especially CaDietary minerals especially Ca2+2+ & P & P Vitamin DVitamin D rickets rickets Vitamin A & CVitamin A & C scurvy (decreases scurvy (decreases

collagen synthesis)collagen synthesis) HormonesHormones

HGHHGH Thyroid hormonesThyroid hormones Sex hormonesSex hormones Calcium metabolism: parathormone, Calcium metabolism: parathormone,

calcitonincalcitonin

Hormone Regulation of Bone GrowthHormone Regulation of Bone Growth Human Growth HormoneHuman Growth Hormone (HGH) (HGH)

Released by pituitary glandReleased by pituitary gland GigantismGigantism: overproduce HGH b4 puberty: overproduce HGH b4 puberty Pituitary DwarfismPituitary Dwarfism: inadequate HGH : inadequate HGH

Sex hormonesSex hormones Speed up bone growth osteoblast activitySpeed up bone growth osteoblast activity

cartilage formationcartilage formation epiphyseal lineepiphyseal line Growth spurtsGrowth spurts Treatment for osteoporosisTreatment for osteoporosis

Calcitonin & parathyroid hormone: Calcitonin & parathyroid hormone: regulate [Caregulate [Ca2+2+] ]

Hormone Regulation of Hormone Regulation of CalciumCalcium [Ca[Ca2+2+] depends on activities of: ] depends on activities of:

– bones (osteoclasts)bones (osteoclasts) Store in bone or release to bloodStore in bone or release to blood

– intestinal tract (absorption)intestinal tract (absorption)– kidneys (excretion)kidneys (excretion)

[Ca[Ca2+2+] maintained by 2 hormones:] maintained by 2 hormones: Calcitonin: Calcitonin: thyroid glandthyroid gland Parathyroid:Parathyroid: parathyroid gland parathyroid gland

Calcitonin & ParathormoneCalcitonin & Parathormone CalcitoninCalcitonin: :

Secreted by thyroidSecreted by thyroid Responds to Responds to

[Ca[Ca2+2+] ] Net effect: [CaNet effect: [Ca2+2+]]

Inhibit Inhibit osteoclastsosteoclasts

Ca intestinal Ca intestinal absorption rateabsorption rate

Ca excretion Ca excretion rate at kidneysrate at kidneys

Parathyroid Parathyroid hormonehormone:: Secreted by Secreted by

parathyroidparathyroid Responds to [CaResponds to [Ca2+2+] ] Net effect: [CaNet effect: [Ca2+2+] ]

Stimulate Stimulate osteoclastsosteoclasts

Ca intestinal Ca intestinal absorption rateabsorption rate

Ca excretion at Ca excretion at kidneyskidneys

Remodeling & Homeostatic Remodeling & Homeostatic MechanismsMechanisms

Osteoblast/ osteoclast activity balancedOsteoblast/ osteoclast activity balanced 18% bone content replaced every year18% bone content replaced every year [Ca[Ca2+2+] must be closely controlled] must be closely controlled

– Hormone Regulation: Calcitonin & Hormone Regulation: Calcitonin & ParathormoneParathormone 30%30% nerves & muscle unresponsive nerves & muscle unresponsive 35%35% convulsions b/c nerves excitable convulsions b/c nerves excitable 50%50% death death

Aging & Skeletal SystemAging & Skeletal System OsteopeniaOsteopenia:: decreasing ossification decreasing ossification

– Reduce bone mass in 30’s & 40’sReduce bone mass in 30’s & 40’s– Osteoblast activity, osteoclast activity normalOsteoblast activity, osteoclast activity normal– Normally, females lose (8% mass), males (3%) Normally, females lose (8% mass), males (3%)

per decadeper decade OsteoporosisOsteoporosis: significant loss of bone mass : significant loss of bone mass

to compromise normal functionto compromise normal function– More in females after menopauseMore in females after menopause– fragilityfragility fx’s & healing impaired (esp. fx’s & healing impaired (esp.

vertebrae)vertebrae)– Treatments (sex hormones: estrogen), Treatments (sex hormones: estrogen),

exercise: slow effects, but can’t preventexercise: slow effects, but can’t prevent

OsteoporosisOsteoporosis

NormalNormal Compression Compression FractureFracture

Bone Repair1.1. BleedBleed fx hematoma fx hematoma2.2. Endosteum & Periosteum cells divideEndosteum & Periosteum cells divide callus callus3.3. Callus middleCallus middle cartilage forms, callus edges cartilage forms, callus edges bone bone4.4. Osteoblasts replace cartilageOsteoblasts replace cartilage spongy bone spongy bone5.5. Bone remodelling by osteoclasts/ blasts x 4 mo- yearBone remodelling by osteoclasts/ blasts x 4 mo- year6.6. Bone starts to Bone starts to remodel with weight bearingremodel with weight bearing

Callus InternalEdge: Bone

Callus ExternalEdge: Bone

Callus Middle:Cartilage

Spinal Fusion w/Spinal Fusion w/Bone GraftBone Graft

Bone Graft

Pedicle Screws

Rod Placement for Displaced Rod Placement for Displaced FxFx

FRACTURES

Anatomy of Bones:Anatomy of Bones:Classification of BonesClassification of Bones

Types/ Types/ Shapes:Shapes:– LongLong– ShortShort– FlatFlat– IrregularIrregular

Examples:Examples:– Humerus, Humerus,

femurfemur– Carpals, Carpals,

tarsalstarsals– Scapula, Scapula,

sternumsternum– VertebraeVertebrae

Examples of Bone ShapesExamples of Bone Shapes

Articulations (joints): Articulations (joints): ClassificationClassification

Functional Classification:Functional Classification: SynarthrosisSynarthrosis: immovable joint: immovable joint

Skull, teeth, epiphyseal plateSkull, teeth, epiphyseal plate AmphiarthrosisAmphiarthrosis: slightly movable: slightly movable

Between tibia & fibula, front of pelvisBetween tibia & fibula, front of pelvis DiarthrosisDiarthrosis: freely movable: freely movable

SynovialSynovial: joint capsule & synovial fluid filled : joint capsule & synovial fluid filled joints (e.g. knee, shoulder, hip)joints (e.g. knee, shoulder, hip)

Types of Diarthrotic JointsTypes of Diarthrotic Joints UniaxialUniaxial

– One directionOne direction– Hinge: elbow, Hinge: elbow,

kneeknee

BiaxialBiaxial– Two directionsTwo directions– Wrist Wrist

Triaxial: Triaxial: 3 directions3 directions– Ball & Socket: hip, Ball & Socket: hip,

shouldershoulder Flex/ ExtendFlex/ Extend Abduct/ AdductAbduct/ Adduct Internal/ External Internal/ External

RotationRotation

– Freely moving joints Freely moving joints are less stableare less stable

– DislocationDislocation= when = when articulating surfaces articulating surfaces are forced out of are forced out of positionposition

General Structures in Diarthrotic General Structures in Diarthrotic JointsJoints

MenisciMenisci: fibrocartilage discs : fibrocartilage discs b/w joint surfacesb/w joint surfaces

Fat padsFat pads: protection & : protection & paddingpadding

Joint capsuleJoint capsule: joint synovial : joint synovial membranemembrane

LigamentsLigamentsBursaeBursae: synovial fluid pockets: synovial fluid pockets

Marrow CavitySpongy Bone

Synovial MembraneArticular CartilageJoint Cavity

Compact Bone

Joint CapsuleBursaMeniscusExtracapsular LigamentIntracapsular Ligament

OsteoarthritisOsteoarthritis

Total Knee & Hip Total Knee & Hip ReplacementsReplacements

Joint Movement Clinical NamesJoint Movement Clinical Names Flexion/ Extension Flexion/ Extension

RotationRotation– Internal or externalInternal or external

Abduction/ AdductionAbduction/ Adduction Specialties:Specialties:

– WristWrist: ulnar & radial deviation: ulnar & radial deviation– Ankle/ footAnkle/ foot: inversion/ eversion: inversion/ eversion– AnkleAnkle: dorsiflexion/ plantarflexion: dorsiflexion/ plantarflexion– ForearmForearm: pronation/ supination: pronation/ supination– ScapulaScapula: elevate/ depress: elevate/ depress