Term
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Definition
- Lining cells retract to expose bone.
- Osteoclasts resorb bone.
- Osteoclasts undergo apoptosis.
- Osteoblasts lay down minerals and matrix.
- Osteblats undergo eithe rof their 3 fates.
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Term
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Definition
Childhood:
- Bone Modeling
- Formation > Resorption
- Osteoblasts > Osteoclasts
Adulthood
- Bone Remodeling
- Formation = Resorption
- Osteoblast = Osteoclasts
Senescence
- Bone Remodeling
- Resorption > Formation
- Osteoclasts > Osteoblasts
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Term
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Definition
- Human RANK: A protein receptor expressed osteoclast precursors
- Human RANK-LIgand: The RANK/RANK-L interactaction in bones stimulate osteoclast activation and differentiation and inhibits osteoclast apoptosis, it promotes bone resorption.
- Osteoprotegrin (OPG):
- OPPOSES RANK/RANL-L
- A decoy receptor for RANK-L made by pre-osteoblasts
- The OPG-RANK interaction causes osteoclasts to undergo apoptosist to promote bone formation
- Sclerostin
- Produced by osteocytes and supresses bone formation
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Term
Fibrodysplasia Ossificans Progressiva (FOP) |
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Definition
- A condition where there is excessive bone growth. Muscle progressively transforms into bone (pathological metamorphosis), creating a 2nd skeleton.
- Ribbons and sheets of bone fuse the jonts of the asiam and appendicular skeleton, entombing the patient in a skeleton of heterotopic (abnormal location) bone.
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Term
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Definition
Fetal skeleton is initially made up of fibrous membranes and hyaline cartilage which begins to ossify at approximatley 7-9 weeks of gestation.
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Term
Intramembranous Ossification |
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Definition
Bone developes from a fibrous membrane from center outwards = membrane bone
Ossification of flat bones, cortical bone, and diploe
- Mesenchymal cells cluster and differentiate into osteoblasts, forming an ossification center in the fibrous conective tissue membrane.
- The osteoblasts begin to secrete osteoid, which is calcified within a few days. Trapped osteoblasts become osteocytes.
- Accumulating osteoid is laid down between embryonic blood vesssels in a random manner. The result is a network of trabeculla called woven bone. Vascularized mesenchyme condesnes on the external face of the woven bone and becomes the periosteum.
- Trabeculae just deep to the periosteum thickens and are later replaced with mature lamellar bone, formign compact bone plates. Diploe persists internally and its vascular tissue beomes red marrow.
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Term
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Definition
Soft spots on a baby's head which , during birth, enable the bony plates of the skull to flex, allowing the child's head to pass through the birth canal.
- If fontanels close too soon the chld will get craniosynotosis (premature cranial suture fusion). Often causes abnormall skull shape, blindness, and mental retardation.
- Noggin, a bone morphogenic protein antagonist, regulates cranial fusion. Found in open, but not fusing together, cranial sutures.
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Term
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Definition
- Bone forms by replacing hyaline cartilage (echondrial bone)
- Begins in the second month of development.
- Uses hyaline cartilage as models for bone construction.
- Requires breakdown of hyaline cartilage prior to ossification.
- Ossification center forms in the center of the bone and a bone collar forms around hyaline cartilage model.
- A cavity forms at the ossification center of the cartilage model.
- internal cavities invade from a periosteal bud and spongy bone forms.
- Mediullar cavity orms; Secondary ossification centers form at epiphyseaes.
- Epiphyses ossify. When completeed hyaline cartilage remain only in the epiphyseal plates and articular cartilage.
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