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25 Cards in this Set
- Front
- Back
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Osteon
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Basic functional unit of the Haversian system
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Components of the Haversian System
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Lamellae, Lacunae, Canaliculi, Haversian canal, Volkmann's canals
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Lamallae
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Ring-like layers of ground substance
Laid down on collagen fiber framework |
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Lacunae
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Spaces between lamellae containing osteocytes
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Canaliculi
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Minute canals radiating from lacunae
Mechanism for communication and transport |
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Haversian canal
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(AKA. Centeral Canal)
Contains blood vessels and nerves Runs "vertically" |
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Volkmann's canals
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Perpendicular channels connecting to Haversian canals
Contains blood vessels and nerves |
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Diaphysis
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Cylinder of compact bone in long bone(shaft) with medullary cavity
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Intermedullary contains
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yellow marrow (adipose)
is enclosed in diaphysis |
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Epiphysis
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Enlarged end of long bone with compact and trabecular bone
Site of red bone marrow at birth (but only in head of humenis and femur in adults) Filled with spongy tissue |
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Metaphysis
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Between diaphysis and epiphysis
Band of cartilage serving as growth plate |
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Periosteum
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Dense irregular connective tissue covering
Covers all compact bone except articular surfaces External surface on which ligaments and tendons attatch |
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Endosteum
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Dense irregular connective tissue covering
Covers all compact bone except articular surfaces Internal (medullary cavity); contains osteoprogenator cells, osteoblasts, and osteoclasts Generally more osteoclastic activity than osteoblast |
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Articular Cartilage
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Layer of hyaline cartilage on articular surface of epiphyses
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Medullary Cavity
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Centeral portion of diaphysis; contains yellow marrow in adults
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Nutrient Foramen
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Opening through compact bone; allows passage of artery into medullary cavity
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Ossification pathways
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Endochondral/Intramembranous
Embryonic bone dvelops from connective tissue model which becomes ossified Ossification is initiated by the invasion of connective tissue by blood vessels Osteoblasts turn connective tissue into trabecular bone at ossification center (non-lamellar--> trabecular) Periosteum develops around connective tissue model Sub-periosteal osteoblasts lay down compact bone on connective tissue model |
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Time frame for ossification
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3-4 months prenatal: primary ossification begins
Birth-5 years: secondary ossification present Adult size and shape starts when the epiphesis and parts of neocranium begin to fuse together |
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Endochondrial Ossification
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Bone forms in hyaline cartilage precursor
Vascularization via nutrient foramen initiates ossification Begins at primary ossification located in the diaphysis, and 1 or more secondary ossification centers located in the ephyses |
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Function of cartilagenous metaphysic
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in Endrochondrial ossification, joins ephisyses and diaphysis of growing long bone (aka growth plate)
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Intramembraneous Ossification
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Bones form within loose or dense connective tissue membrane
Mesencymal cells differentiate into osteoblasts; put out osteoid fluid Initially produces trabecular bone, then compact bone Development path for clavicle, mandible, flat cranial bones |
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Purpose of continuing remodeling, rebuilding post-ossification
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Maintain calcium and phosphate levels in the body
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How post-ossification bone change works
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Deposition and reabsorption occurs on periosteal and endosteal surfaces off the skeletal element
Osteoblast/clast activity regulated by hormones Diamater increases through deposition>eating |
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Osteopenia and Osteoporosis
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Increased absorption and decreased production with age leads to loss of bone mass
Linked to estrogen production Underlies loss in height, teeth and brittle bones When normal function is impaired=osteoperosis |
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Osteomalcia
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(AKA Rickets) Due to vitamin D deficencies
Also lack of calcium and phosphorus absorption=reduced mineral content in bones Can occur in children or adults |
