SKELETAL SYSTEM _____________________ Developed by Will Kleinelp Associate Professor Department of...

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


proximal epiphysisproximal epiphysis

metaphysismetaphysis

diaphysisdiaphysis


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


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


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


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.


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


•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


•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

SKELETAL SYSTEM _____________________ Developed by Will Kleinelp Associate Professor Department of...

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