Download - The Skeletal System Skeletal system includes: Skeletal system includes: –bones of the skeleton –cartilages, ligaments, and connective tissues

The Skeletal SystemThe Skeletal System• Skeletal system includes:Skeletal system includes:

– bones of the skeletonbones of the skeleton– cartilages, ligaments, and connective cartilages, ligaments, and connective

tissuestissues

Functions of the Functions of the Skeletal SystemSkeletal System1.1. SupportSupport2.2. Storage of minerals (calcium)Storage of minerals (calcium)3.3. Storage of lipids (Storage of lipids (yellow marrowyellow marrow))

Functions of the Functions of the Skeletal SystemSkeletal System4.4. Blood cell production (Blood cell production (red marrowred marrow))5.5. ProtectionProtection6.6. Leverage (force of motion)Leverage (force of motion)

Classification of BonesClassification of Bones• Bone are identified by:Bone are identified by:

– shapeshape– internal tissuesinternal tissues– bone markingsbone markings

Bone ShapesBone Shapes1.1. Long bonesLong bones2.2. Flat bonesFlat bones3.3. Sutural bonesSutural bones4.4. Irregular bonesIrregular bones5.5. Short bonesShort bones6.6. Sesamoid bonesSesamoid bones

Long BonesLong Bones

Figure 6–1a

Long BonesLong Bones• Are long and thinAre long and thin• Are found in arms, legs, hands, feet, Are found in arms, legs, hands, feet,

fingers, and toes fingers, and toes

Flat BonesFlat Bones

Figure 6–1b

Flat BonesFlat Bones• Are thin with parallel surfacesAre thin with parallel surfaces• Are found in the skull, sternum, ribs, Are found in the skull, sternum, ribs,

and scapulaand scapula

Sutural BonesSutural Bones

Figure 6–1c

Sutural BonesSutural Bones• Are small, irregular bonesAre small, irregular bones• Are found between the flat bones of Are found between the flat bones of

the skullthe skull

Irregular Bones Irregular Bones

Figure 6–1d

Irregular Bones Irregular Bones • Have complex shapes Have complex shapes • Examples:Examples:

– spinal vertebrae spinal vertebrae – pelvic bones pelvic bones

Short BonesShort Bones

Figure 6–1e

Short BonesShort Bones• Are small and thickAre small and thick• Examples:Examples:

– ankle ankle – wrist boneswrist bones

Sesamoid BonesSesamoid Bones

Figure 6–1f

Sesamoid BonesSesamoid Bones• Are small and flatAre small and flat• Develop inside tendons near joints of Develop inside tendons near joints of

knees, hands, and feetknees, hands, and feet

Bone MarkingsBone Markings• Depressions or grooves:Depressions or grooves:

– along bone surfacealong bone surface• Projections:Projections:

– where tendons and ligaments attachwhere tendons and ligaments attach– at articulations with other bones at articulations with other bones

• Tunnels:Tunnels:– where blood and nerves enter bonewhere blood and nerves enter bone

Bone MarkingsBone Markings

Table 6–1 (2 of 2)

Long BonesLong Bones• The The femurfemur

Figure 6–2a

Long BonesLong Bones• DiaphysisDiaphysis: :

– the shaft the shaft • EpiphysisEpiphysis: :

– wide part at each endwide part at each end– articulation with other bonesarticulation with other bones

• MetaphysisMetaphysis: : – where diaphysis and epiphysis meetwhere diaphysis and epiphysis meet

The DiaphysisThe Diaphysis• A heavy wall of A heavy wall of compact bonecompact bone, or, or

dense bonedense bone• A central space called A central space called marrow cavitymarrow cavity

The Epiphysis The Epiphysis • Mostly Mostly spongyspongy (cancellous)(cancellous) bonebone • Covered with compact bone (Covered with compact bone (cortexcortex))

Flat BonesFlat Bones• The The parietal boneparietal bone of the skull of the skull

Figure 6–2b

Flat BonesFlat Bones• Resembles a sandwich of spongy Resembles a sandwich of spongy

bonebone• Between 2 layers of compact boneBetween 2 layers of compact bone

Bone (Bone (OsseousOsseous) Tissue ) Tissue • Dense, supportive connective tissueDense, supportive connective tissue• Contains specialized cellsContains specialized cells• Produces solid matrix of calcium salt Produces solid matrix of calcium salt

depositsdeposits• Around collagen fibersAround collagen fibers

Characteristics of Bone Characteristics of Bone TissueTissue• Dense Dense matrixmatrix, containing:, containing:

– deposits of calcium saltsdeposits of calcium salts– bone cellsbone cells within within lacunaelacunae organized organized

around blood vesselsaround blood vessels

Characteristics of Bone Characteristics of Bone TissueTissue• CanaliculiCanaliculi: :

– form pathways for blood vesselsform pathways for blood vessels– exchange nutrients and wastesexchange nutrients and wastes

Characteristics of Bone Characteristics of Bone TissueTissue• PeriosteumPeriosteum: :

– covers outer surfaces of bones covers outer surfaces of bones – consist of outer consist of outer fibrousfibrous and inner and inner

cellularcellular layers layers

Matrix MineralsMatrix Minerals• 2/3 of bone matrix is 2/3 of bone matrix is calcium calcium

phosphatephosphate, Ca, Ca33(PO(PO44))22::– reacts with reacts with calcium hydroxidecalcium hydroxide, Ca(OH), Ca(OH)22 – to form crystals of to form crystals of hydroxyapatitehydroxyapatite, ,

CaCa1010(PO(PO44))66(OH)(OH)22

– which incorporates other calcium salts which incorporates other calcium salts and ionsand ions

Matrix ProteinsMatrix Proteins• 1/3 of bone matrix is protein fibers 1/3 of bone matrix is protein fibers

((collagencollagen))

Bone CellsBone Cells• Make up only 2% of bone mass:Make up only 2% of bone mass:

– osteocytesosteocytes– osteoblastsosteoblasts– osteoprogenitor cellsosteoprogenitor cells– osteoclastsosteoclasts

OsteocytesOsteocytes• Mature bone Mature bone

cells that cells that maintain the maintain the bone matrixbone matrix

Figure 6–3 (1 of 4)

OsteocytesOsteocytes• Live in Live in lacunaelacunae • Are between layers (Are between layers (lamellaelamellae) of ) of

matrixmatrix• Connect by cytoplasmic extensions Connect by cytoplasmic extensions

through through canaliculicanaliculi in lamellae in lamellae• Do not divideDo not divide

Osteocyte FunctionsOsteocyte Functions• To maintain protein and mineral To maintain protein and mineral

content of matrixcontent of matrix• To help repair damaged boneTo help repair damaged bone

OsteoblastsOsteoblasts • Immature bone Immature bone

cells that secrete cells that secrete matrix matrix compounds compounds ((osteogenesisosteogenesis))


OsteoidOsteoid• Matrix produced by osteoblasts, but Matrix produced by osteoblasts, but

not yet calcified to form not yet calcified to form bonebone• Osteoblasts surrounded by bone Osteoblasts surrounded by bone

become become osteocytesosteocytes

Osteoprogenitor CellsOsteoprogenitor Cells • Mesenchymal stem cells that divide Mesenchymal stem cells that divide

to produce osteoblaststo produce osteoblasts


Osteoprogenitor Cells Osteoprogenitor Cells • Are located in inner, cellular layer of Are located in inner, cellular layer of

periosteum (periosteum (endosteumendosteum))• Assist in fracture repairAssist in fracture repair

OsteoclastsOsteoclasts • Secrete acids and protein-digesting enzymesSecrete acids and protein-digesting enzymes


Osteoclasts Osteoclasts • Giant, mutlinucleate cellsGiant, mutlinucleate cells• Dissolve bone matrix and release Dissolve bone matrix and release

stored minerals (stored minerals (osteolysisosteolysis))• Are derived from stem cells that Are derived from stem cells that

produce macrophagesproduce macrophages

HomeostasisHomeostasis• Bone building (by osteocytes) and Bone building (by osteocytes) and

bone recycling (by osteoclasts) must bone recycling (by osteoclasts) must balance:balance:– more breakdown than building, bones more breakdown than building, bones

become weakbecome weak– exercise causes osteocytes to build exercise causes osteocytes to build

bonebone

Compact BoneCompact Bone

Figure 6–5

OsteonOsteon• The basic unit of mature compact The basic unit of mature compact

bonebone• Osteocytes are arranged in Osteocytes are arranged in

concentric lamellaeconcentric lamellae• Around a Around a central canalcentral canal containing containing

blood vesselsblood vessels

Perforating CanalsPerforating Canals• Perpendicular to the central canalPerpendicular to the central canal• Carry blood vessels into bone and Carry blood vessels into bone and

marrowmarrow

Circumferential LamellaeCircumferential Lamellae• Lamellae wrapped around the long Lamellae wrapped around the long

bonebone• Binds osteons togetherBinds osteons together

Spongy BoneSpongy Bone

Figure 6–6

Spongy BoneSpongy Bone• Does not have osteonsDoes not have osteons• The matrix forms an open network of The matrix forms an open network of

trabeculaetrabeculae• Trabeculae have no blood vesselsTrabeculae have no blood vessels

Red MarrowRed Marrow• The space between trabeculae is The space between trabeculae is

filled with filled with red bone marrowred bone marrow::– which has blood vesselswhich has blood vessels– forms red blood cellsforms red blood cells– and supplies nutrients to osteocytesand supplies nutrients to osteocytes

Yellow MarrowYellow Marrow• In some bones, spongy bone holds In some bones, spongy bone holds

yellow bone marrowyellow bone marrow::– is yellow because it stores fatis yellow because it stores fat

Weight–Bearing BonesWeight–Bearing Bones

Figure 6–7

Weight–Bearing BonesWeight–Bearing Bones• The femur transfers weight from hip The femur transfers weight from hip

joint to knee joint:joint to knee joint:– causing causing tensiontension on the lateral side of the on the lateral side of the

shaftshaft– and and compressioncompression on the medial side on the medial side

Periosteum and EndosteumPeriosteum and Endosteum• Compact bone is covered with Compact bone is covered with

membrane:membrane:– periosteumperiosteum on the outside on the outside – endosteumendosteum on the inside on the inside

PeriosteumPeriosteum

Figure 6–8a

PeriosteumPeriosteum• Covers all bones:Covers all bones:

– except parts enclosed in joint capsulesexcept parts enclosed in joint capsules• It is made up of:It is made up of:

– an outer, fibrous layeran outer, fibrous layer– and an inner, cellular layerand an inner, cellular layer

Perforating FibersPerforating Fibers• Collagen fibers of the periosteum:Collagen fibers of the periosteum:

– connect with collagen fibers in boneconnect with collagen fibers in bone– and with fibers of joint capsules, and with fibers of joint capsules,

attached tendons, and ligamentsattached tendons, and ligaments

Functions of PeriosteumFunctions of Periosteum1.1. Isolate bone from surrounding Isolate bone from surrounding

tissuestissues2.2. Provide a route for circulatory and Provide a route for circulatory and

nervous supplynervous supply3.3. Participate in bone growth and Participate in bone growth and

repairrepair

EndosteumEndosteum

Figure 6–8b

EndosteumEndosteum• An incomplete cellular layer:An incomplete cellular layer:

– lines the marrow cavitylines the marrow cavity– covers trabeculae of spongy bonecovers trabeculae of spongy bone– lines central canalslines central canals

EndosteumEndosteum• Contains osteoblasts, Contains osteoblasts,

osteoprogenitor cells, and osteoprogenitor cells, and osteoclastsosteoclasts

• Is active in bone growth and repairIs active in bone growth and repair

Bone DevelopmentBone Development• Human bones grow until about age Human bones grow until about age

2525• OsteogenesisOsteogenesis::

– bone formationbone formation• OssificationOssification: :

– the process of replacing other tissues the process of replacing other tissues with bonewith bone

OssificationOssification• The 2 main forms of ossification are:The 2 main forms of ossification are:

– intramembranous ossificationintramembranous ossification– endochondral ossificationendochondral ossification

Endochondral OssificationEndochondral Ossification• Ossifies bones that originate as Ossifies bones that originate as

hyaline cartilagehyaline cartilage• Most bones originate as hyaline Most bones originate as hyaline

cartilagecartilage

Endochondral OssificationEndochondral Ossification• Growth and ossification of long bones Growth and ossification of long bones

occurs in 6 stepsoccurs in 6 steps

Endochondral Endochondral Ossification: Step 1Ossification: Step 1

• Chondrocytes in the center Chondrocytes in the center of hyaline cartilage:of hyaline cartilage:– enlargeenlarge– form struts and calcifyform struts and calcify– die, leaving cavities in die, leaving cavities in

cartilagecartilage

Figure 6–9 (Step 1)

Endochondral Endochondral Ossification: Step 2Ossification: Step 2• Blood vessels grow around the edges Blood vessels grow around the edges

of the cartilage of the cartilage • Cells in the perichondrium change to Cells in the perichondrium change to

osteoblasts: osteoblasts: – producing a layer of superficial bone producing a layer of superficial bone

around the shaft which will continue to around the shaft which will continue to grow and become compact bone grow and become compact bone (appositional growth)(appositional growth)


• Blood vessels enter the Blood vessels enter the cartilage:cartilage:– bringing fibroblasts that bringing fibroblasts that

become osteoblastsbecome osteoblasts– spongy bone develops at spongy bone develops at

the the primary ossification primary ossification centercenter




• Remodeling creates a Remodeling creates a marrow cavitymarrow cavity::– bone replaces cartilage at bone replaces cartilage at

the the metaphysesmetaphyses


• Capillaries and Capillaries and osteoblasts enter the osteoblasts enter the epiphyses:epiphyses:– creating creating secondary secondary

ossification centersossification centers


Endochondral Endochondral Ossification: Step 6Ossification: Step 6• Epiphyses fill with spongy bone:Epiphyses fill with spongy bone:

– cartilage within the joint cavity is cartilage within the joint cavity is articulation cartilagearticulation cartilage

– cartilage at the metaphysis is cartilage at the metaphysis is epiphyseal cartilageepiphyseal cartilage

• Appositional growthAppositional growth::– compact bone thickens compact bone thickens

and strengthens long bone and strengthens long bone with layers of with layers of circumferential lamellaecircumferential lamellae

Endochondral OssificationPLAYFigure 6–9 (Step 2)

Endochondral OssificationEndochondral Ossification

Epiphyseal LinesEpiphyseal Lines

Figure 6–10

Epiphyseal LinesEpiphyseal Lines• When long bone stops growing, after When long bone stops growing, after

puberty:puberty:– epiphyseal cartilage disappears epiphyseal cartilage disappears – is visible on X-rays as an is visible on X-rays as an epiphyseal lineepiphyseal line

RemodelingRemodeling• The adult skeleton:The adult skeleton:

– maintains itselfmaintains itself– replaces mineral reserves replaces mineral reserves

• RemodelingRemodeling::– recycles and renews bone matrix recycles and renews bone matrix – involves osteocytes, osteoblasts, and involves osteocytes, osteoblasts, and

osteoclasts osteoclasts

Functions of CalciumFunctions of Calcium• Calcium ionsCalcium ions are vital to: are vital to:

– membranesmembranes– neuronsneurons– muscle cells, especially heart cellsmuscle cells, especially heart cells

Calcium RegulationCalcium Regulation• Calcium ions in body fluids:Calcium ions in body fluids:

– must be closely regulatedmust be closely regulated• Homeostasis is maintained:Homeostasis is maintained:

– by by calcitonincalcitonin and and parathyroid hormoneparathyroid hormone– which control storage, absorption, and which control storage, absorption, and

excretionexcretion

Calcitonin and Parathyroid Calcitonin and Parathyroid Hormone ControlHormone Control• Bones:Bones:

– where calcium is storedwhere calcium is stored• Digestive tract:Digestive tract:

– where calcium is absorbedwhere calcium is absorbed• Kidneys:Kidneys:

– where calcium is excretedwhere calcium is excreted

CalcitoninCalcitonin• Secreted by Secreted by C cellsC cells (parafollicular (parafollicular

cells)cells) in in thyroidthyroid•DecreasesDecreases calcium ion levels by: calcium ion levels by:

– inhibiting osteoclast activityinhibiting osteoclast activity– increasing calcium excretion at kidneysincreasing calcium excretion at kidneys


The Major Types of The Major Types of Fractures Fractures

• Pott’s fracturePott’s fracture


• Comminuted Comminuted fracturesfractures



• Transverse fracturesTransverse fractures



• Spiral fracturesSpiral fractures




• Displaced fracturesDisplaced fractures



• Colles’ fractureColles’ fracture



• Greenstick fractureGreenstick fracture



• Epiphyseal fracturesEpiphyseal fractures



• Compression fracturesCompression fractures

Download - The Skeletal System Skeletal system includes: Skeletal system includes: –bones of the skeleton –cartilages, ligaments, and connective tissues

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