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17 Cards in this Set
- Front
- Back
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six functions of the skeletal system |
- support: soft parts anchored to bones give body its general shape - protection: important organs housed within bony structures - movement & locomotion: bones serve as system of levels/fulcra that are manipulated by muscles, cartilages provide surfaces for joints - mineral sink: bones made up of mineral salts that play imp. roles in other systems (nervous/muscular/circular) -site of hemopoietic tissue: red marrow; blood cell & osteoclast production - site of energy storage: yellow marrow for fat storing |
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two components of skeletal system |
cartilage & bone are connective tissues that include large quantities of matrix composed of protein fibers and a ground substance that may be gelatinous or mineralized |
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cartilage structure |
- surface invested with layer of dense, irregular connective tissue called perichondrium where blood vessels/nerves reside - cells called chondrocytes located in spaces called lacunae - matrix of protein fibers (collagen, elastic, reticular) w/ ground substance called chondroitan sulfate - cells nourished by diffusion through matrix *sometimes calcified by deposition of calcium salts in matrix; not ossification* |
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bone structure |
- a type of connective tissue that consists of living cells (osteocytes) and collagen fibers embedded in a matrix heavily impregnated with calcium salts - surface is covered by periostium - protein fibers give bone resilience, resistance to tensilve forces, torsion - give slight ability to bend - Ca salts give it great strength, resistance to compression forces - two types: spongy and compact |
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compact bone |
- laid down as a series of concentric layers of matrix called lamellae - a group of lamella that sourrounds a Haversian canal called osteon - osteocytes occupy lacunae and are connected by canaliculi |
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spongy bone (= cancellous) |
- consists of trabeculae (thin bony splits that traverse inner space w/in bone) - no osteons but osteocytes still located in lacunae w/ canaliculi - form along lines of stress, adding strength by serving as struts w/o the weight - spaces in spongy bone are filled with red marrow; contains highly vascularized hemopoietic tissue |
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long bone (wtf?) |
within hollow space of the shaft of a long bone, there's yellow marrow filled with adipose tissue for energy storage structure: diaphysis ; epiphysis ; metaphysis ; articular cartilage ; periosteum ; medullary (marrow) cavity ; endosteum |
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osteogenesis |
bone formation develops in two distinct ways: - dermal bone - endochondral ossification |
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three categories of bone cells & definitions |
osteocytes: occupy lacunae within mature bone osteoblasts: secrete bone matrix around themselves, producing new bone; dervied from osteogenic cells osteoclasts: actively dissolve bone |
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dermal bone |
= membrane bone; ossifies directly in connective tissue of fibrous membranes - originate as centers of ossification where collagen fibers are deposited in an irregular mesh work - calcium salts precipitate out & around collagen fibers, producing trabeculae which continue to be formed from center -- out until functional size reacher - oter portions of trab. are remodeled as compact bone |
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diploe |
in flattened bones |
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endochondral ossification |
- originate as cartilagiouns models (formed from mesenchyme), complete with perichondrium - osteoblasts form on the inner surface of the pericho. and begin to lay down bone in a cylinder called the periostial collar - cartilage of diaphysis is invaded by bone-forming tissues that lay down meshwork of trabec. - primary ossification center - cartilaginous metaphyses remain at the ends of the diaphysis - secondary ossification centers develop in ends of bone and give rise to epiphyses |
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bone growth: thickness |
bone grows in thickness as osteoblasts continue to lay down new lamellae on inner/outer surfaces differential growth: outer surface grows rapidly, inner surface undergoes negative growth as more bone is resorbed than deposited |
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bone growth: length |
- growth occurs in metaphyses - new cartilage continues to be produced on epiphyseal side - chondrocytes swell and die as they are further removed from the blood vessels of the epiphysis on the diaphyseal side - cartilage around dead chondrocytes become calcified ; invaded by new bone forming tissue from below(w/ blood vessels, osteoclasts, osteoblasts) -these lay down new osteons in diaphyseal side; diaphysis increases in length |
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bone growth: epiphyseal plates |
growth ceases when chondrocytes in the epiphyseal plates stop dividing cartilage of E plate is then entirely replaced w/ bone, often leaving a telltale groove called the epiphyseal line |
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bone growth: remodelling |
- bone is continuously resorbed and deposited even after closure of epiphyses - usually occurs in response to external stimuli (nutrition, exercise, injury, etc) - bone resorbed when osteoclasts release protein digesting enzymes and acids (former break down collagen fibers in bone while latter dissolves calcified matrix) - osteoclats phagocytize whole bone fragments; bone redepositied in areas that need strengthening |
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distribution of bone types in the skeleton |
dermal bone: clavicles, interclavicles, sesamoids (scales of fish, osteoderms of reptiles, most of turtle shells, external skull bones) endochondral bone: the entire rest of the skeleton |
