:Title:

Introduction to the Skeleton

Copyright 2010 Pearson Education, Inc.Bones and Skeletal TissueThe human skeleton is made of both cartilage and bone tissue.An infants skeleton is primarily cartilage but as the infants grows it is replaced by bone.Copyright 2010 Pearson Education, Inc.Figure 6.17 Fetal primary ossification centers at 12 weeks.

Parietal boneRadiusUlnaHumerusFemurOccipital boneClavicleScapulaRibsVertebraIliumTibiaFrontal boneof skull MandibleCopyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.Skeletal CartilageCartilage consists primarily of water. This provides resilience and compressibility that protects the bones.There are three types:Copyright 2010 Pearson Education, Inc.Skeletal CartilageCartilage consists primarily of water. This provides resilience and compressibility that protects the bones.There are three types:HyalineElasticFibrocartilageCopyright 2010 Pearson Education, Inc.Hyaline CartilageMost abundantChondrocytes appear sphericalCollagen is the only fiberLocations:Articular cartilageCostal cartilageRespiratory cartilageNasal cartilage

Copyright 2010 Pearson Education, Inc.Fibro elastic CartilageVery compressible, chondrocytes are found in parallel rowsFound only in vertebral discs and meniscus of the knee.

Copyright 2010 Pearson Education, Inc.Elastic CartilageSimilar to hyaline but contains elastic fibersFound in areas where there is repeated bendingTwo locations:External earEpiglottis

Copyright 2010 Pearson Education, Inc.Figure 6.1 The bones and cartilages of the human skeleton.

Axial skeletonAppendicular skeletonHyaline cartilagesElastic cartilagesFibrocartilagesCartilagesBones of skeletonEpiglottisLarynxTracheaCricoidcartilageLungRespiratory tube cartilagesin neck and thoraxThyroidcartilageCartilage inexternal earCartilages innoseArticularCartilageof a jointCostalcartilageCartilage inIntervertebraldiscPubicsymphysisArticular cartilageof a jointMeniscus (padlikecartilage inknee joint)Copyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.PerichondriumThis supplies nutrients via diffusion to the avascular cartilage.This limits the thickness of the cartilage.

Copyright 2010 Pearson Education, Inc.ChondrocytesThe chondrocyte is the cell responsible for the maintenance and growth of the cartilage.They reside in lacunae

Copyright 2010 Pearson Education, Inc.Cartilage GrowthCartilage can grow two ways:Appositional growth Interstitial growthCopyright 2010 Pearson Education, Inc.Appositional GrowthAppositional growth (from the edges) occurs where cells from the perichondrium lay down new a cartilage matrix.

Copyright 2010 Pearson Education, Inc.Interstitial GrowthGrowth from inside the cartilage. The chondrocytes divide in the lacunae laying down more matrix.

Copyright 2010 Pearson Education, Inc.Skeletal ClassificationThere are 206 bones in the adult skeleton.

Copyright 2010 Pearson Education, Inc.Skeletal ClassificationThe skeleton is divided into the:Axial SkeletonAppendicular Skeleton

Copyright 2010 Pearson Education, Inc.Axial SkeletonForms the long axis of the body.Its primary roll is support and protection of the organs.

Copyright 2010 Pearson Education, Inc.Appendicular SkeletonBones of the upper and lower limbs including the shoulder and hips. It is involved in locomotion.

Copyright 2010 Pearson Education, Inc.Bone Classification Bones are further classified by shape. There are 4 types:Long BonesShort BonesFlat BonesIrregular BonesCopyright 2010 Pearson Education, Inc.Long BonesAre longer than wide. It consists of a shaft plus two ends.

Copyright 2010 Pearson Education, Inc.Long BonesAre longer than wide. It consists of a shaft plus two ends.Found on the Appendicular Skeleton.

Copyright 2010 Pearson Education, Inc.Long BonesAre longer than wide. It consists of a shaft plus two ends.Found on the Appendicular Skeleton.Size doesnt matterFemur vs phalanges

Copyright 2010 Pearson Education, Inc.Short BonesTypically cube shape. These are found on the wrist (carpals) and ankle (tarsals)

Copyright 2010 Pearson Education, Inc.Flat BonesAre flat and thin in 1 dimension.Often have a curve edgeExamples include ribs, scapula and skull

Copyright 2010 Pearson Education, Inc.Irregular ShapeNo specific shape, examples include the pelvic bones and vertebrae.

Copyright 2010 Pearson Education, Inc.Figure 6.2 Classification of bones on the basis of shape.

(a)Long bone(humerus) (b)Irregular bone(vertebra), rightlateral view(d)Short bone(talus) (c)Flat bone(sternum) Copyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.Function of the Skeletal SystemSupport- respirationProtection-skullMovement-Appendicular skeletonMineral Storage-calcium phosphateBlood Cell Formation- HematopoiesisFat StorageCopyright 2010 Pearson Education, Inc.Gross anatomy of BoneThe surface of the bone is covered by projections and ridges that serve as attachment points for ligaments and tendons.Examples include:TrochantersSpines &GroovesCopyright 2010 Pearson Education, Inc.

Copyright 2010 Pearson Education, Inc.Gross anatomy of BoneBone is can be classified as compact or spongy bone.

Copyright 2010 Pearson Education, Inc.Gross anatomy of BoneCompact bone is dense and has a smooth outer surface.

Copyright 2010 Pearson Education, Inc.Gross anatomy of BoneSpongy bone has a honey comb structure made up of small projections called trabeculae.

Copyright 2010 Pearson Education, Inc.Structure of the long boneDiaphysis is the long central shaft of a long boneCopyright 2010 Pearson Education, Inc.Structure of the long boneDiaphysis is the long central shaft of a long boneEpiphyses are the ends of the boneCopyright 2010 Pearson Education, Inc.Structure of the long boneDiaphysis is the long central shaft of a long boneEpiphyses are the ends of the boneMembranes cover the exterior and interior of the bonesCopyright 2010 Pearson Education, Inc.Structure of the long boneDiaphysis is the long central shaft of a long boneEpiphyses are the ends of the boneMembranes cover the exterior and interior of the bonesComposed both of compact and spongy boneCopyright 2010 Pearson Education, Inc.Structure of the long bone The diaphysis has a large central cavity and is filled with fat (yellow marrow).

Copyright 2010 Pearson Education, Inc.Structure of the long bone The epiphyses are filled with hematopoietic tissue (red marrow) which gives rise to the blood cells.

Copyright 2010 Pearson Education, Inc.Structure of the long boneThe periosteum covers the exterior of the bone.

It contains bone forming cells and is involved with bone growing wider.Copyright 2010 Pearson Education, Inc.

Proximal epiphysis(a)Epiphyseal lineArticularcartilagePeriosteumSpongy boneCompact boneMedullarycavity (linedby endosteum)DiaphysisDistal epiphysisCopyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.

(c)Yellowbone marrowEndosteumCompact bonePeriosteumPerforating(Sharpeys) fibersNutrientarteriesFigure 6.3c The structure of a long bone (humerus of arm).Copyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.Microscopic Anatomy of BoneFour cell types populate the bone tissues.These are: Osteogenic cells Osteoblasts Osteocytes OsteoclastsCopyright 2010 Pearson Education, Inc.Microscopic Anatomy of Bone Osteogenic cells are stem cells that give rise to other bone forming cellsCopyright 2010 Pearson Education, Inc.Microscopic Anatomy of BoneOsteoblasts are bone forming cells

Osteocytes maintains the bone matrix

Osteoclasts destroy bone

Copyright 2010 Pearson Education, Inc.Figure 6.4 Comparison of different types of bone cells.

(a) Osteogenic cell(b) Osteoblast(c) OsteocyteStem cellMature bone cellthat maintains thebone matrixMatrix-synthesizingcell responsiblefor bone growth(d) OsteoclastBone-resorbing cellCopyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.Microscopic Anatomy Compact BoneThe structural unit of the compact bone is the osteon or Haversian System.

It consists of a central canal that contains blood vessels and nerves.Copyright 2010 Pearson Education, Inc.Microscopic Anatomy Compact BoneBranches from the nerves and blood vessels go transversely through Volkmann's canals.Copyright 2010 Pearson Education, Inc.Figure 6.7 Microscopic anatomy of compact bone.

Endosteum lining bony canalsand covering trabeculaePerforating (Volkmanns) canalPerforating (Sharpeys) fibersPeriosteal blood vesselPeriosteumLacuna (withosteocyte) (a)(b)(c)LacunaeLamellaeNerveVeinArteryCanaliculiOsteocytein a lacunaCircumferentiallamellaeOsteon(Haversian system)Central(Haversian) canalCentralcanalInterstitial lamellaeLamellaeCompactbone Spongy boneCopyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.Microscopic Anatomy Compact BoneOsteocytes are found in the lacunae.

Copyright 2010 Pearson Education, Inc.Figure 6.7c Microscopic anatomy of compact bone.

Lacuna (with osteocyte) (c)LacunaeLamellaeCentralcanalInterstitial lamellaeCopyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.Bone Formation (Remodeling)Bone has an inorganic and organic component.

The inorganic component is calcium phosphate.The organic component is made up of collagen and proteoglycans.Copyright 2010 Pearson Education, Inc.Bone Formation (Remodeling)Bone is unique because is can repair itself and adjust to mechanical stresses.

Copyright 2010 Pearson Education, Inc.Bone Formation (Remodeling)Bone is unique because is can repair itself and adjust to mechanical stresses.

This is a complex process involving a tug of war between Osteoclasts and Osteoblasts.

Copyright 2010 Pearson Education, Inc.Bone Formation (Remodeling)Hormones such as Calcitonin (PHT), sex and growth hormones and vitamins such as Vitamin D are involved in this process.

Copyright 2010 Pearson Education, Inc.Figure 6.12 Parathyroid hormone (PTH) control of blood calcium levels.

Osteoclastsdegrade bonematrix and release Ca2+into blood.ParathyroidglandsThyroidglandParathyroidglands releaseparathyroidhormone (PTH).StimulusFalling bloodCa2+ levelsPTHCalcium homeostasis of blood: 911 mg/100 mlBALANCEBALANCECopyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.Bone Formation (Remodeling)Wolfs law governs how a bone remodels.

Compression and tension work together to shape a bone.

For example, a persons dominate arm has a thicker bone structure.

Copyright 2010 Pearson Education, Inc.Figure 6.13 Bone anatomy and bending stress.

Load here (body weight)Head offemurCompressionherePoint ofno stressTensionhereCopyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.Figure 6.14 Vigorous exercise can lead to large increases in bone strength.

Cross-sectionaldimension of the humerusAddedbone matrixcounteractsadded stress(b) Serving arm(a)Nonserving armCopyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.Bone Formation (Remodeling)Bones can grow two ways:1) Longitudinal growth occurs in long bones between the diaphysis and epiphysis, along a region called the epiphyseal plate.

Cartilage expands and is replaced by bone.

Copyright 2010 Pearson Education, Inc.Bone Formation (Remodeling)Bones can grow two ways:2) Appositional growth (width) occurs between the periosteum and endosteum.

Copyright 2010 Pearson Education, Inc.Figure 6.11 Long bone growth and remodeling during youth.

Bone growthBone remodelingArticular cartilageEpiphyseal plateCartilagegrows here. Cartilageis replacedby bone here.Cartilagegrows here. Bone isresorbed here. Bone isresorbed here. Bone is addedby appositionalgrowth here. Cartilageis replacedby bone here.Copyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.Diseases & Injuries of the BoneFractures are the most common injury to bone. Most fractures will heal with time.Copyright 2010 Pearson Education, Inc.Diseases & Injuries of the BoneFractures are the most common injury to bone. Most fractures will heal with time.

Copyright 2010 Pearson Education, Inc.Diseases & Injuries of the Bone

Copyright 2010 Pearson Education, Inc.Diseases & Injuries of the Bone

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Table 6.2 Common Types of Fractures (1 of 3)Copyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.66

Table 6.2 Common Types of Fractures (2 of 3)Copyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.67

Table 6.2 Common Types of Fractures (3 of 3)Copyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.68Diseases & Injuries of the BoneOsteoporosis is a disease of old age and is a major cause of hip fractures. The bone mass decreases. It is typically diagnosed with a bone density test.Copyright 2010 Pearson Education, Inc.

Figure 6.16 The contrasting architecture of normal versus osteporotic bone.Copyright 2010 Pearson Education, Inc.Copyright 2010 Pearson Education, Inc.70Diseases & Injuries of the Bone

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Copyright 2010 Pearson Education, Inc.Diseases & Injuries of the BoneRickets and Osteomalacia results in soft bones. Ricketts is a child hood disease while Osteomalacia is in adults.

Rickets is often due to a Vitamin D deficiency.Copyright 2010 Pearson Education, Inc.Diseases & Injuries of the Bone

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