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SKELETAL SYSTEM
SKELETAL SYSTEM
__________________________________________Developed byDeveloped by
Will KleinelpWill KleinelpAssociate ProfessorAssociate Professor
Department of BiologyDepartment of Biology©2006©2006
__________________________________________Developed byDeveloped by
Will KleinelpWill KleinelpAssociate ProfessorAssociate Professor
Department of BiologyDepartment of Biology©2006©2006
FunctionsFunctions1. Support
A. Body Framework2. Movement
A. Muscle attachment to skeletonB. Movable Joints
3. ProtectionA. Vital Organs
4. Mineral ReservoirA. Storage of Calcium, Phosphorus, Sodium,
Potassium5. Hemopoiesis
A. Bone Marrow produces blood cells 5. Triglyceride storage
A. yellow bone marrow
1. SupportA. Body Framework
2. MovementA. Muscle attachment to skeletonB. Movable Joints
3. ProtectionA. Vital Organs
4. Mineral ReservoirA. Storage of Calcium, Phosphorus, Sodium,
Potassium5. Hemopoiesis
A. Bone Marrow produces blood cells 5. Triglyceride storage
A. yellow bone marrow
Classifications
Classifications
Axial SkeletonAxial Skeleton Appendicular SkeletonAppendicular Skeleton
Classes of Bones
Classes of Bones
LongLong ShortShort
FlatFlat
IrregularIrregular
SesamoidSesamoid
Gross
Structure
Gross
Structure
articular cartilagearticular cartilage
epiphyseal plateepiphyseal plate
red bone marrowred bone marrow
cancellous bonecancellous bone
endosteumendosteum
compact bonecompact bone
periosteumperiosteum
medullary canalmedullary canal
nutrient artery & foramennutrient artery & foramen
articular cartilagearticular cartilage
proximal epiphysisproximal epiphysis
metaphysismetaphysis
diaphysisdiaphysis
metaphysismetaphysis
distal epiphysisdistal epiphysis
Microscopic StructureStructure
Microscopic StructureStructure
blood vesselblood vessel
lamellaelamellae
concentric lamellaeconcentric lamellae
interstitial lamellaeinterstitial lamellae
circumferential lamellae
circumferential lamellae
central Haversian canalcentral Haversian canal
osteocyteosteocyte
canaliculicanaliculi
lacnuaelacnuae
Volkman’s canalVolkman’s canal
osteonosteon
compact bonecompact bone
spongy bonespongy bone
trabeculaetrabeculae
Bone CellsBone CellsBone CellsBone Cells
osteogenic cellosteogenic cell
osteoblastosteoblast
osteocyteosteocyte
osteoclastosteoclast
Blood Supply - Long BonesBlood Supply - Long BonesBlood Supply - Long BonesBlood Supply - Long Bones
articular cartilagearticular cartilage
epiphyseal artery & veinepiphyseal artery & vein
epiphyseal lineepiphyseal line
metaphyseal artery & veinmetaphyseal artery & vein
periosteumperiosteum
periosteal artery & veinperiosteal artery & vein
medullary cavitymedullary cavity
nutrient foramennutrient foramen
nutrient artery & veinnutrient artery & vein
epiphysisepiphysis
metaphysismetaphysis
diaphysisdiaphysis
OsteogenesisOsteogenesisOsteogenesisOsteogenesis
There are two major forms of ossificationThere are two major forms of ossification
A. Intramembranous Ossification• originating tissue is fibrous membranous connective tissue• involves the bones of skull, mandible and clavicle• first process to begin roughly 4-6 weeks in utero
A. Intramembranous Ossification• originating tissue is fibrous membranous connective tissue• involves the bones of skull, mandible and clavicle• first process to begin roughly 4-6 weeks in utero
B. Intramembranous Ossification• originating tissue is hyaline cartilage• involves all bones other than skull, mandible and clavicle
B. Intramembranous Ossification• originating tissue is hyaline cartilage• involves all bones other than skull, mandible and clavicle
Fetus is comprised of loose mesenchymal cells shaped like little bones and provide a template for the
overall process of ossification. Ossification begins at about six weeks and continues until final closure at 20-25 years.
Fetus is comprised of loose mesenchymal cells shaped like little bones and provide a template for the
overall process of ossification. Ossification begins at about six weeks and continues until final closure at 20-25 years.
Intramembranous Intramembranous OssificationOssification
Intramembranous Intramembranous OssificationOssification
★Ossification Center DevelopmentOssification Center Development
★ Calcification Calcification
★Trabecular Formation Trabecular Formation
★Periosteum FormationPeriosteum Formation
★Ossification Center DevelopmentOssification Center Development
★ Calcification Calcification
★Trabecular Formation Trabecular Formation
★Periosteum FormationPeriosteum Formation
Four Process Involved:Four Process Involved:Four Process Involved:Four Process Involved:
Ossification Center Ossification Center DevelopmentDevelopment
Ossification Center Ossification Center DevelopmentDevelopment✴ the bone model consists of fibrous membranous connective tissue
✴ under specific chemical messengers fetal mesenchymal cells condense and begin to differentiate
✴ some differentiate into blood vessels while other differentiate into osteoblasts - committed bone forming cells
✴ the osteoblasts secrete collagen-proteoglycan tendriles that are able to bind to calcium salts
✴ through this binding, the PREBONE or OSTEOID matrix becomes calcified
✴ the bone model consists of fibrous membranous connective tissue
✴ under specific chemical messengers fetal mesenchymal cells condense and begin to differentiate
✴ some differentiate into blood vessels while other differentiate into osteoblasts - committed bone forming cells
✴ the osteoblasts secrete collagen-proteoglycan tendriles that are able to bind to calcium salts
✴ through this binding, the PREBONE or OSTEOID matrix becomes calcified
CalcificationCalcificationCalcificationCalcification✴ the secretion of the extracellular matrix stops and the osteoblasts are separated from the calcified matrix by a layers of the osteoid matrix they secrete
✴ the osteoblasts become trapped in the calcified matrix and become osteocytes - or bone cells
✴ as calcification proceeds, bony spicules radiate out from the region where ossification began
✴ the secretion of the extracellular matrix stops and the osteoblasts are separated from the calcified matrix by a layers of the osteoid matrix they secrete
✴ the osteoblasts become trapped in the calcified matrix and become osteocytes - or bone cells
✴ as calcification proceeds, bony spicules radiate out from the region where ossification began
Trabecular FormationTrabecular FormationTrabecular FormationTrabecular Formation✴ as the calcified spicules form, they fuse and develops large spacial areas called trabeculae
✴Trabeculae fuse with one another and form the spongy bone where blood vessels fill the trabecular spaces
✴connective tissue associated with the blood vessels in the trabeculae differentiates into red one marrow
✴ as the calcified spicules form, they fuse and develops large spacial areas called trabeculae
✴Trabeculae fuse with one another and form the spongy bone where blood vessels fill the trabecular spaces
✴connective tissue associated with the blood vessels in the trabeculae differentiates into red one marrow
Periosteum Periosteum FormationFormationPeriosteum Periosteum FormationFormation
✴ the entire region of calcified spicules become surrounded by compact mesenchymal cells that form the periosteum
✴the cells on the surface become osteoblasts and deposit an osteoid matrix to that of the pre-exiting spicules forming the layers of compact bone on the outside
✴ the entire region of calcified spicules become surrounded by compact mesenchymal cells that form the periosteum
✴the cells on the surface become osteoblasts and deposit an osteoid matrix to that of the pre-exiting spicules forming the layers of compact bone on the outside
Endochondral OssificationEndochondral OssificationEndochondral OssificationEndochondral OssificationCARTILAGE MODEL DEVELOPMENT
•The original model is mesenchymal connective tissue•Specific chemical messengers cause the mesenchymal cells to crowd together in the shape of the future bone•The mesenchymal cells differentiate into chrondroblasts - cartilage forming cells•The chondroblasts secrete and extracellular matrix producing a cartilage model consisting of hyaline cartilage•A membrane called the perichondium forms around the perimeter of the model
CARTILAGE MODEL GROWTH
•The chondroblasts become embedded in the cartilage extracellular matrix•Interstitial growth - or growth in length - occurs by continuous cell division of the chondrocytes and additional matrix secretion.•Appositional growth - or growth in diameter - is accomplished by adding more extracelllar matrix to the perimeter of the cartilage model and on the surface.•As the cartilage template grows chondrocytes in the mid-region increase in size (hypertrophy) and the surrounding extracellular matrix begins to calcify•Chondrocytes now lying within the calcified matrix die and their empty spaces now form lacunae. The lacunae merge together and form small cavities within the bone.
CARTILAGE MODEL DEVELOPMENT
•The original model is mesenchymal connective tissue•Specific chemical messengers cause the mesenchymal cells to crowd together in the shape of the future bone•The mesenchymal cells differentiate into chrondroblasts - cartilage forming cells•The chondroblasts secrete and extracellular matrix producing a cartilage model consisting of hyaline cartilage•A membrane called the perichondium forms around the perimeter of the model
CARTILAGE MODEL GROWTH
•The chondroblasts become embedded in the cartilage extracellular matrix•Interstitial growth - or growth in length - occurs by continuous cell division of the chondrocytes and additional matrix secretion.•Appositional growth - or growth in diameter - is accomplished by adding more extracelllar matrix to the perimeter of the cartilage model and on the surface.•As the cartilage template grows chondrocytes in the mid-region increase in size (hypertrophy) and the surrounding extracellular matrix begins to calcify•Chondrocytes now lying within the calcified matrix die and their empty spaces now form lacunae. The lacunae merge together and form small cavities within the bone.
PRIMARY OSSIFICATION CENTERPRIMARY OSSIFICATION CENTER
•Nutrient arteries now penetrate the perichondrium and the calcifying cartilage model through a nutrient foramen in the mid-region of the model•this stimulates the osteogenic cells in the perichondrium to differentiate into osteoblasts•Once the periosteum starts to from bone it becomes the periosteum•In the midsection, periosteal capillaries grow into the disintegrating calcified cartilage and form the primary ossification center•It is at this center that bone tissue will replace most of the cartilage•The osteoblasts begin to deposit bone extracellular matrix over the remaining calcified cartilage forming the spongy trabeculae
PRIMARY OSSIFICATION CENTERPRIMARY OSSIFICATION CENTER
•Nutrient arteries now penetrate the perichondrium and the calcifying cartilage model through a nutrient foramen in the mid-region of the model•this stimulates the osteogenic cells in the perichondrium to differentiate into osteoblasts•Once the periosteum starts to from bone it becomes the periosteum•In the midsection, periosteal capillaries grow into the disintegrating calcified cartilage and form the primary ossification center•It is at this center that bone tissue will replace most of the cartilage•The osteoblasts begin to deposit bone extracellular matrix over the remaining calcified cartilage forming the spongy trabeculae
Endochondral OssificationEndochondral OssificationEndochondral OssificationEndochondral Ossification
Endochondral OssificationEndochondral OssificationEndochondral OssificationEndochondral Ossification
Medullary Canal FormationMedullary Canal Formation
•osteoclasts start to break down some of the newly formed spongy bone in the mid section•this destruction results in a cavity in the middle of the bone called the medullary cavity in the diaphysis of the forming bone•the walls of the diaphysis will be replaced by compact bone
Medullary Canal FormationMedullary Canal Formation
•osteoclasts start to break down some of the newly formed spongy bone in the mid section•this destruction results in a cavity in the middle of the bone called the medullary cavity in the diaphysis of the forming bone•the walls of the diaphysis will be replaced by compact bone
Secondary Ossification Center FormationSecondary Ossification Center Formation
•Epiphyseal arteries enter the epiphyses of the bone and cause the development of secondary ossification centers at the proximal and distal epiphyses•Secondary ossification begins shortly after birth•Development occurs in the same mode as the primary ossification center BUT the spongy bone remains in the interior of the epiphyses•Secondary ossification proceeds outward towards the outer surface of the bone.
Secondary Ossification Center FormationSecondary Ossification Center Formation
•Epiphyseal arteries enter the epiphyses of the bone and cause the development of secondary ossification centers at the proximal and distal epiphyses•Secondary ossification begins shortly after birth•Development occurs in the same mode as the primary ossification center BUT the spongy bone remains in the interior of the epiphyses•Secondary ossification proceeds outward towards the outer surface of the bone.
Endochondral OssificationEndochondral OssificationEndochondral OssificationEndochondral Ossification
Articular Cartilage FormationArticular Cartilage Formation
•The hyaline cartilage that coves the ends of the bone forms the articular cartilage•Hyaline cartilage also remains between the diaphysis and the epiphyseal ends forming the epiphyseal plate, and will remain until adulthood
Articular Cartilage FormationArticular Cartilage Formation
•The hyaline cartilage that coves the ends of the bone forms the articular cartilage•Hyaline cartilage also remains between the diaphysis and the epiphyseal ends forming the epiphyseal plate, and will remain until adulthood
Bone GrowthBone GrowthBone GrowthBone GrowthArticular Cartilage FormationArticular Cartilage Formation
•During childhood bone grows in thickness by appositional growth•The long bones increase in length by the addition of bone material of the diaphyseal side of the epiphyseal plate by interstitial growth
Articular Cartilage FormationArticular Cartilage Formation
•During childhood bone grows in thickness by appositional growth•The long bones increase in length by the addition of bone material of the diaphyseal side of the epiphyseal plate by interstitial growth
epiphyseal endepiphyseal end
dipahyseal enddipahyseal end
zone of resting cartilagezone of resting cartilage
zone of proliferating cartilagezone of proliferating cartilage
zone of hypertrophic cartilagezone of hypertrophic cartilage
zone of calcified cartilagezone of calcified cartilage
diaphysisdiaphysis
•this zone is nearest the epiphysis•contains scatted chondrocytes•cells are non-functional•function to anchor epiphyseal plate to epiphysis
•this zone is nearest the epiphysis•contains scatted chondrocytes•cells are non-functional•function to anchor epiphyseal plate to epiphysis
•contains chondrocytes•arranged like coin stacks•function to replace dying chondrocytes at the diaphyseal end of the epiphyseal plate
•contains chondrocytes•arranged like coin stacks•function to replace dying chondrocytes at the diaphyseal end of the epiphyseal plate
•consists of large maturing chondrocytes structured in columns•consists of large maturing chondrocytes structured in columns
•only a few cells in thickness of dean chondrocytes•extracellular matrix surrounding chondrocytes is calcified•osteoclasts dissolve calcified cartilage replacing with osteoblasts and bone•osteoblasts lay down new bone forming a new diaphysis
•only a few cells in thickness of dean chondrocytes•extracellular matrix surrounding chondrocytes is calcified•osteoclasts dissolve calcified cartilage replacing with osteoblasts and bone•osteoblasts lay down new bone forming a new diaphysis
Factors Affecting Bone Factors Affecting Bone GrowthGrowth
Factors Affecting Bone Factors Affecting Bone GrowthGrowth
•Minerals•Calcium•Phosphorous•Fluoride•magnesium•iron•manganese
•Vitamins•C•K•B-12
•Hormones•IGF•thyrocalcitonin•thyroxin•parathyroid hormone•testosterone•estrogen
•Minerals•Calcium•Phosphorous•Fluoride•magnesium•iron•manganese
•Vitamins•C•K•B-12
•Hormones•IGF•thyrocalcitonin•thyroxin•parathyroid hormone•testosterone•estrogen
FracturesFracturesFracturesFractures