Physiology of Bone Formation, Remodeling, and Metabolism.pdf
stages of bone formation
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Transcript of stages of bone formation
Growth and Growth and Development of BoneDevelopment of Bone
IntroductionIntroduction
Bone is a relatively hard and lightweight Bone is a relatively hard and lightweight composite material, formed mostly of composite material, formed mostly of calcium phosphate calcium phosphate
Bone can be either Bone can be either compactcompact or or cancellouscancellous (spongy). (spongy). CorticalCortical (outer (outer layer) bone is compact layer) bone is compact
Cortical bone accounts for 80% of the total Cortical bone accounts for 80% of the total bone mass of the adult skeleton bone mass of the adult skeleton
Types Of BonesTypes Of Bones
Long BonesLong Bones Short BonesShort Bones Flat BonesFlat Bones Irregular BonesIrregular Bones Pneumatic BonesPneumatic Bones Sessamoid BonesSessamoid Bones
Bone cellsBone cells OsteoblastsOsteoblasts are typically viewed as bone forming cells. are typically viewed as bone forming cells. OsteocytesOsteocytes originate from osteoblasts which have originate from osteoblasts which have
migrated into and become trapped and surrounded by migrated into and become trapped and surrounded by bone matrix which they themselves produce. bone matrix which they themselves produce.
OsteoclastsOsteoclasts are the cells responsible for bone are the cells responsible for bone resorption. Osteoclasts are large, multinucleated cells resorption. Osteoclasts are large, multinucleated cells located on bone surfaceslocated on bone surfaces
Lining Cells Lining Cells come from osteoblasts which have become come from osteoblasts which have become flattenedflattened. . Bone lining cells have flat organelles so they Bone lining cells have flat organelles so they can easily cover the bone without interfering with other can easily cover the bone without interfering with other cells functionscells functions. .
Developmental ClassificationDevelopmental Classification Membranous BonesMembranous Bones ossify in membrane ossify in membrane
(intramembramous or mesenchymal Ossification). Eg. (intramembramous or mesenchymal Ossification). Eg. Bones of Vault of Skull & Facial BonesBones of Vault of Skull & Facial Bones
Cartilagenous BonesCartilagenous Bones ossify in cartilage ossify in cartilage (intracartelagenous or endochondral Ossification). Eg. (intracartelagenous or endochondral Ossification). Eg. Bones of Limbs, Vertebral Column & Thoracic CageBones of Limbs, Vertebral Column & Thoracic Cage
Membrano-Cartilagenous BonesMembrano-Cartilagenous Bones ossify partly in ossify partly in membrane and partly in cartilage. Eg. Clavicle, Mandible, membrane and partly in cartilage. Eg. Clavicle, Mandible, Occipital, Temporal, SphenoidOccipital, Temporal, Sphenoid
Intramembranous OssificationIntramembranous Ossification
Intramembranous ossificationIntramembranous ossification is one of is one of the two essential processes the two essential processes duringduring fetalfetal development of the development of the skeletal skeletal systemsystem by which rudimentaryby which rudimentary bone bone tissuetissue is created.is created.
Stages of Intramembranous Stages of Intramembranous OssificationOssification
Stages of Intramembranous Stages of Intramembranous OssificationOssification
Stages of Intramembranous Stages of Intramembranous OssificationOssification
Stages of Intramembranous Stages of Intramembranous OssificationOssification
Endochondral OssificationEndochondral Ossification
Begins in the second month of Begins in the second month of developmentdevelopment
Uses hyaline cartilage “bones” as models Uses hyaline cartilage “bones” as models for bone constructionfor bone construction
Requires breakdown of hyaline cartilage Requires breakdown of hyaline cartilage prior to ossificationprior to ossification
Formation of bone collar around hyaline cartilage model.
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Cavitation of the hyaline cartilage within the cartilage model.
Invasion of internal cavities by the periosteal bud and spongy bone formation.
5 Ossification of the epiphyses; when completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages
Formation of the medullary cavity as ossification continues; appearance of secondary ossification centers in the epiphyses in preparation for stage 5.
Hyaline cartilage
Primary ossification center
Bone collar
Deteriorating cartilage matrix
Spongy bone formation
Blood vessel of periosteal bud
Secondary ossification centerEpiphyseal
blood vessel
Medullary cavity
Epiphyseal plate cartilage
Spongy bone
Articular cartilage
Stages of Endochondral OssificationStages of Endochondral Ossification
Bone ResorptionBone Resorption While osteoblasts and osteocytes are adding While osteoblasts and osteocytes are adding
new bone to the outer surface, osteoclasts are new bone to the outer surface, osteoclasts are removing bone at the inner surface and removing bone at the inner surface and enlarging the marrow cavityenlarging the marrow cavity
Osteoclasts make contact with the bone through Osteoclasts make contact with the bone through a region referred to as ruffled border and a region referred to as ruffled border and subsequently have the ability to degrade both subsequently have the ability to degrade both inorganic and organic matrices of the boneinorganic and organic matrices of the bone
Types of MarrowTypes of Marrow
Red marrow – chief blood cell forming Red marrow – chief blood cell forming organ of the adult and is found in spongy organ of the adult and is found in spongy bone of the epiphysis of long bones and bone of the epiphysis of long bones and main bodies of ribs, sternum and main bodies of ribs, sternum and vertebraevertebrae
Yellow marrow – composed mainly of Yellow marrow – composed mainly of adipose tissue and found in the medullary adipose tissue and found in the medullary cavity of bonescavity of bones
Bone RemodelingBone Remodeling Osteoblasts form osteons (basic functional unit of Osteoblasts form osteons (basic functional unit of
compact bone) by osteogenesis whereas osteoclasts compact bone) by osteogenesis whereas osteoclasts destroy osteons by resorption. destroy osteons by resorption.
The balance between these two yields net bone The balance between these two yields net bone depositiondeposition
As animals age, bone resorption may exceed formation As animals age, bone resorption may exceed formation and bone mass decreasesand bone mass decreases
Bones grow through a process of Appositional Growth- Bones grow through a process of Appositional Growth- Formation of new bone on the surface of older bone or Formation of new bone on the surface of older bone or cartilagecartilage
Long Bone Growth and RemodelingLong Bone Growth and Remodeling
Osteoblasts beneath the periosteum secrete bone matrix, forming ridges that follow the course of periosteal blood vessels.
1 2 3 4As the bony ridges enlarge and meet, the groove containing the blood vessel becomes a tunnel.
The periosteum lining the tunnel is transformed into an endosteum and the osteoblasts just deep to the tunnel endosteum secrete bone matrix, narrowing the canal.
As the osteoblasts beneath the endosteum form new lamellae, a new osteon is created. Meanwhile new circumferential lamellae are elaborated beneath the periosteum and the process is repeated, continuing to enlarge bone diameter.
Artery Periosteum Penetrating canalCentral canal of osteonPeriosteal ridge
Appositional Growth of BoneAppositional Growth of Bone
Bone Formation Of MandibleBone Formation Of Mandible
Factors affecting bone growth and Factors affecting bone growth and remodelingremodeling
A lot of bone remodeling is a result of A lot of bone remodeling is a result of hormonal action.hormonal action.
Hormones involved in bone growth and Hormones involved in bone growth and remodeling is remodeling is PTHPTH and and CalcitoninCalcitonin
CalcitoninCalcitonin is released by the thyroid gland is released by the thyroid gland that decreases osteoclasts yielding that decreases osteoclasts yielding decreased mobilization of calcium from decreased mobilization of calcium from bone and decreasing blood calcium bone and decreasing blood calcium concentrationsconcentrations
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