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186 Cards in this Set
- Front
- Back
four components of the skeltetal system
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bones, carilage, tendons, and ligaments
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function of the skeletal system is to
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provide support and protection, allow body movements, store minerals and fats, and is site of blood cell production
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bones are good for support because
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they are rigid and strong allowing them to support major tissue in body
carilage - firm yet flexable support ligaments - hold bones together |
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ligaments
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strong bands of fiberous connective tissue. allow some movement between bones but prevent excessive movements
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bones are good for protection because
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hard thereby able to protect organs it surrounds
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bones are good for movements because
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contractions of skeletal muscle moves bondes
joints - allow movement smooth cartilage covers ends of bones within some joints and helps allow movement ligaments provide some movement but prevents excessive movements |
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tendons
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strong bands of conective tissue
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joints
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formed where two or more bones come together and allow movement between the bones
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bones are good for storage because
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some minerals in the blood are taken to the bone and stored and then used when needed. mostly calcium and phosphorus. sometimes fats
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if needed fats are released from bone into the ___ and __.
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blood and used by other tissues as a source of energy.
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bones are good for blood cell production because
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many bones contain cavities filled with red bone marrow which gives rise to blood cells and platelets
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types of carilage
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hyaline cartilage, fibrocartilage, and elastic cartilage
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which type of carilage is most intimately associated with bone?
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hyaline cartilage
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most of the bones in the body develop from
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hyaline cartilage
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hyaline cartilage is also important to growth in bone because
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growth in length of bones and bone repair often involve the production of hyaline cartilage until it is then replaced with bone
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hyaline cartilage consistes of specialized cells that
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produce a matrix surrounding the cells
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cells that produce new cartilage matrix are called
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chondroblast
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when a matrix surrounds a chondroblast it becomes a
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chondrocyte
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a chondrocyte is
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a rounded cell that occupies a space called a lacuna within the matrix
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matrix contains __ which do ___ and ___ which do ___.
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collagen which provides strength and proteoglycans which make cartilage resilient by trapping water
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what is a perichondrum
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a double-layered connective tissue sheath covering most cartilage
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outer layer of the perichondrum is
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dense irregular connective tissue containing fibroblasts
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what do nutrients have to do to reach the chondrocytes and why
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blood vessels and nerves penetrate the outer layer of the perichondrium but do not enter the cartilage matrix so that nutrients must diffuse through the cartilage matrix to reach the chondrocytes
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the inner layer of the perichondrum differs from the outer layer in that...
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is more delicate and has fwer fibers and contains chondroblast
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articular cartilage
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is cartilage covering the ends of bones where they come together to form joints and has no perichondrium, blood vessels, or nerves.
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two ways in which cartlilage grows
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appositional growth and intersitial growth
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appositional growth
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chondroblasts in the perichondrium lay down new matrix and add new chondrocytes to outside of tissue
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interstitial growth
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chondrocytes within the tissue divide and add more matrix between the cells
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the composition of the bone matrix is responsible for
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the characterisitics of bone`
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bone cells produce the bone matrix become
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entrapped within it, break it down so that new matrix can replace the old matrix
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by weight mature bone matrix is normally what percent organic and inorganic?
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35% organic and 65% inorganic material
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organic material consists primarly of
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collagen and proteoglycans
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inorganic material consists primarily of
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calcium phosphate crystal called hydroxyapatite whos formula is Ca10(PO4)6(OH)2
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___ and ___ are responsible for the major functional characteristics of the bone
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collagen and mineral components
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bone matrix might be said to resemble
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reinforced concrete
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collagen might be said to resemble
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reinforcing steel bars, because it lends flexible strength to the matrix
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mineral components can be said to resemble
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concrete because it gives the matix compression (weight-bearing) strenght
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if all mineral is removed from a long bone..
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collagen becomes the primary consituent and bone becomes overly flexable
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if all the collagen is removed from a long bone...
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mineral becomes the main consituent and the bone becomes very brittle and is easily shattered
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bone cells are catergorized as...
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osteoblasts, osteocytes, and osteoclasts
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osteoblasts
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have extensive endoplasmic reticulum and numerous ribosomes
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osteoblast produce
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collagen and proteoglycans which are packaged into vesicles by Golgi apparatus and released from the cell by exocytosis
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osteoblasts release
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matrix vesicles
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matrix vesicles
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are membrane-bound sacs formed when the plasma membrane buds or protrudes outward and pinches off
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matrix vesicles concentrate
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Ca^2+ and PO4^3- and form needlelike hydroxyapatite crystals
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when hydroxyapatite crystals are released from the matrix vesicles
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they act as templates or "seeds" whuch stimulate further hydroxapatite formation and mineralization fo the materix
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ossification/ osteogenesis
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the formation of bone by osteoblasts
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ossification occurs by
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appositional growth on the surface of previously existing bone or cartilage
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elongated cell processed from osteoblast connect to
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cell procceses of other osteoblasts through gap junctions
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bone matrix produced by the osteoblasts cover the
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older bone surface and surrounds the osteoblast cell bodies and processes. the result is a new layer of bone.
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osteoctye
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an osteoblast that has become surrounded by bone matrix. it is now a mature bone cell
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osteocytes become relatively
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inactive compared with most osteoblast but they can produce the components needed to maintain the bone matrix
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lacunae
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the spaces occupied by the osteocyte cell bodies
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canliculi
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the spaces occupied by the osteoctye cell process
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cells and their proccessed form
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a "mold" around which the matrix is formed
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bones differ from cartilage in that
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the procceses of bone cells are in contact wih one another through canaliculi. instead of diffusing through the mineralized matrix nutrients and gases can pass through the small amount of fluid surrounding the celss in the canaliculi and lacunae or pass from cell to cell through the gap junctions connection the cell process
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osteoclasts
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large cells with several nuclei and are responsible for reorption
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reorption
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breakdown of bone
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ruffled border
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where the plasma membrane or osteoclasts contacts bone matrix and forms many projections
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osteoclasts also release
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enzymes that digest the protein components of the matrix
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through the process of endocytosis some of the breakdown products of bone resorption are
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taken into the osteoclast
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osteoclast break down bone best when
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they are in direct contact with mineralized bone matrix
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osteoblasts assist in the
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resorption fo bone by osteoclasts by production enzymes that break down the thin layer of unmineralized organic matrix normally covering bone.
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removeal of the thin layer of unmineralized organic matrix by osteoblast enables
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the obsteoclasts to come into contact with the mineralized bone
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connective tissue develops
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embryologically from mesenchymal cells
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some mesenchymal cells become
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stem cells
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stem cells can
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relicate and give rise to more specialized cell types
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osteochondral progenitor cells
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stem cells that can become osteoblast or chondroblast
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osteochondral progenitor cells are located
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in the inner layer of the perichondrium, the inner layer of the periosteum, and the endosteum
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osteoblasts are derived from
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osteochondral progenitor cells
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osteocytes are derived from
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osteoblasts
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osteoclast are derived from
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stem cells that give rise to a type of white blood cell called a monocyte
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multinucleated osteoclast probably results from
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the fusion of many stem cell descendants
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bone tissue is classified as either
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woven or lamellar bone according to the organization of collagen fibers within the bone matrix
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woven bone
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the collagen fibers are randomly oriented in many directions
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woven bone is first formed
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during fetal development or during the repair of a fracture
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remodeling
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the process of removing old bone and adding new bone
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woven bone is remodeled to form
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lamellar bone
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lamellar bone
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is mature bone that is organized into thin sheetw or layers called lamellae
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collagen fibers of one lamella lie __ to one another but ___ to the collagen fibers in the adjacent lamellae
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parallel
at an angle |
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bones can also be classified according to
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the amount of bone matrix relative tot the amount of space present within the bone
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concellous bone
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consists of interconnecting rods or plates of bone called trabeculae
has less bone matrix and more space than compact bone is sometimes called spongy bone |
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between the trabeculae are spaces that
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are filled with bone marrow and blood vessels
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usually no blood vessels penetrate the trabeculae so
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osteocytes must obtain nutrients through their canaliculi
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trabeculae are located
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along the lines of stress within a bone
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compact bone
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is denser and has fewer spaces than cancellous bone
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in compact bone blood vessesls enter
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the substance of the none itself
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lamellae of compact bone are pimarily oriented
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blood vessels that run parrallel to the long axiz of the bone and are contained withine central or haversain canals
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in compact bone central cannals are lined with
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endosteum and contain blood vessels, nerves, and loose connective tissue
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concentric lamellae
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circular layers of bone latrix that surroung a common center, the central cannal
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osteon or haversain system
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a unit-- a singe central canal, its contents, and associated concentric lamellae and osteocytes--the bulls eye
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in compact bone, osteocytes are located
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in lacunae between the lamellar rings and canaliculi radiate between lacunaw accros the lamellae
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the outer surfaces of compact bone are formed by
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circumferential lamellae
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circumferential lamellae
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thin plates that extend around the bone
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in compact bone--in between osteons are
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intersitial lamellae
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intersitial lamellae
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remnants of concentric or circumferntial lamellae that were partially removed during bone remodeling
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in compact bone--osteocytes reviece nutrients and eliminate waste products through
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the canal system within compact bone
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blood vessels from the periosteum or medullary cavity enter the bone through
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perforating or Volkmann's cannals which run perpendicular to the lond axis of the bone
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perforating canals are not surrounded by concentric lamellae but
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can pass throught the concentric lamellae of osteons
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central canals recieve blood vesels from
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perforating canals
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individual bones are classified
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accorging to their shape as long, flat, or irregular
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long bones
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are longer than they are wide most of the bones of the upper and lower limbs are long bones
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short bones
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are about as broad as they are long they are nearly cube-shaped or round and are exemplified by the bones of the wrist and ankle
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flat bones
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have relativly thin, flattened shape and are usually curved. ex ribs, sternum and shoulder blades
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irregular bones
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have shapes that do not readily fit into the other three categories ex. vertebrae and facial bones
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diaphysis
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shaft of the long bone and is composed primarily of compact bone but can contain cancelous bone
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the end of the long bone is made mostly of
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cancellous bone with outer layer of compact bone
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withine joing, the end of the long bone is covered with hyaline cartilage called
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articular cartilage
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during bone formation and growth bones develop
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from centers of ossification
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primary center of ossification is in the
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diaphysis
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epiphysis
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a part of a long bone that develops from a center of ossification distinct from that of the diaphysis
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epiphyseal or growth plate
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seperates the epiphysis from the diaphysis
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growth in bone lenght occurs at
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the epiphyseal plate
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epiphyseal line
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when bone stops growing in lenght the epiphyseal plate becomes ossified and is called this
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the diaphysis of a long bone can have a large internal space called the
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medullary cavity
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cavities of cancellous bone and the medullary cavity are filled with
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marrow
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red marrow is
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the site of blood cell formation
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yellow marrow ia
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mostly adipose tissue
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in fetus spaces are mostly filled with __ marrow
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red marrow
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conversion of red marrow to yellow marrow begins
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just before birth and continues well into adulthood
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___ marrow completly replaces ___ marrow in the long bones of the limbs (ex. proximinal of arm and thigh bones)
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yellow replaces red
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which bone is used when donating red marrow?
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hip bone because it is a large bone with more marrow than smaller bones and accessed relatively easily
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periosteum
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a connective tissue membrane that covers the outer surface of a bone
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in a long bone, the outer fibrous layer is
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dense irregular collagenous connective tissue that contains blood vessels and nerves
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in a long bone, the inner layer is
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a single layer of bone cells which includes oseoblasts, osteoclasts, and osteochondral progenitor cells
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in long bones, where tendons and ligaments attach to bone
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the collagen fibers of the tendon or ligament become continuous with those of the perosteu
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perforating or Sharpey's fibers
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collagen fibers of the tendons or ligaments that penetrate the preriosteum into the outer part of the bone and they strengthen the attachment of the tendons or ligaments to the bone
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endosteum
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single layer of cells that lines the internal surfaces of all cavities within bones
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flat bones contain
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an interior framework of cancellous bone sandwiched between two layers of compact bone
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short and irregular bones have a compositions similar to the
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epiphysis of long bones
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which bones are not eglongated and have no diaphyses
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short and irregular
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which bones posses epiphyseal growth plates and therefore have small epiphyses
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some irregular
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sinuses
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air-filled spaces found is some in some of the flat and irregular bones of the skull which are lined by mucous membrane
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during fetal developemnt bone formation occurs in two patters..
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intramembranous and endochondral ossification
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intramembranous ossification takes place in
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connective tissue membranes
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endochondral ossification ossicifation takes place in
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cartilage
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both intramembranous and endochondral ossification initially produce
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woven bone which is then remodeled after remondeling
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at about the fifth week of development
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embryonic mesenchyme condenses around the developing brain to form a membrane of connective tissue with randomly oriented delicate collagen fibers
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intramembranous ossification of the membrane begins
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at about the eighth week of development and is completed by age 2
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centers of ossification
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locations in the membrane where ossification begins and they expand to form a bone by gradually ossifying the membrane
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fontanels
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the larger membrane-covered spaces between the developing skull bones that have not yet been ossified. are soft spots (bones eventually grow together and usually closed by 2 years old)
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intramembranous ossificationb begins when
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some of the mesenchymal celss in the membrane become osteochondral progenitor celss which specialise to become osteoblasts
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osteoblasts become osteocytes how?
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osteoblasts produce bone matirx that surroungs the collagen fibers of the connective tissue membrane and then the osteoblsts become osteocytes
(as a result many tiny tracevulae of woven hone develop) |
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the formation of caritlage begins
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at approximately the end of the fourth week of development
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endochondral ossification of some cartilage might not begin
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until as late as age 18-20 years
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bones of the base of the skull, part of the mandible, the epiphyses of the clavivles and most of the remaining skeletal system develop
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through the process of endochondral ossification
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unlike cartilage bones cannont grow by
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interstitial growth
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bones increase in size only by
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appositional growth
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appositional growth
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the formation of new bone on the surface of older bone or cartilage
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long bones and bony projections increase in length because of
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growth at the epiphyseal plate
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in a long bone the epiphyseal plate separates
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the epiphysis from the diaphysis
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growth at the epiphyseal plate involves
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the formation of new cartilage by intersitial cartilage growth followed by apposistional bone growth on the surface of the cartilage
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what are teh 4 zones of the epiphyseal plate?
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1. zone of resting cartilage
2. zone of proliferation 3. zone of hypertrophy 4. zone of calification |
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zone of resting cartilage
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nearest the epiphysis and contains randomly arranged chondrocytes that do not divide rapidly
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zone of perliferation
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the chondrocytes in this zone produce new cartilage though intersitial cartilage growth
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zone of hypertrophy
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the condrocytes produce in the zone of proliferation mature and enlarge. Thus a maturation gradient exists in each column: the cells nearer the epiphysis are younger and are actively proliferating whereas teh celss progressively nearer the diaphysis are older and are undergoing hypertrophy
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zone of calicification
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very thin and contains hypertrophied chondrocytes and calcified cartilage matrix. the hypertropheid condrocytes die and blood vessles contains osteoblasts from the endosteum. the osteoblasts line up on the surface of the calcified cartilage and through apposistional bone growth deposit new bone matrix which is later remodeled
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the process of cartilage calcification and ossification in the epiphyseal plate occurs by
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the same basic process as the calcification adn ossification of the cartilage model during endochondral bone formation
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the overall lenght of the diaphysis increases when
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new cartilage cells from in the zone of proliferation and as these celss enlarge in the zone of hyperthrophy
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why doesnt the thickness of the epiphyseal plate not increase
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because the rate of cartilage growth on the epiphyseal side of the plate is equal to the rate at which cartilage is replaced by none of the diaphyseal side of the plate
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as the bones achieve normal adult size, growth in bone length stopes because
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the epiphyseal plate is ossified and becomes the epiphyseal line (occures betweeen age 12 and 25)
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epiphyses increase in size because of
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growth at the articular cartilage
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bones that do not have an epiphysis, such as short bones, increase in size by
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growth at the epiphysis
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when epiphysis reach their full size the growth of ___ and its replaced by __ cease.
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cartilage
bone |
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what type of bone doesnt stop growing?
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articular cartilage
it persists through life and doesn not become ossified like the epiphyseal plate |
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when bone growth in width is rapid as in young bones or during puberty
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osteoblasts from the preiosteum lay down bone to form a series of ridges with grooves and one or more blood vessels of preiosteum lie within each groove
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when bone growth is slow
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the surface of the bone becomes smooth as osteoblast from the periosteum lay down even layers of bone to form circumferential lamellae
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potential shape and size of a bone and an idividual's final height are determined not only genetically but also by
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nutrition and hormmones
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any metabolic disorder that can affect the rate of cell proliferation or the production of collagen and other matrix can
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affect bone growth as does the avialibility of calcium or other minerals needed in the mireralization process
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arrested growth
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transverse regions of greater bone denisty crossing an otherwise normal bone
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vitamin D is nessisary in bone growth because
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it is nessiary for normal absorption of calcium from the intestines
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insufficient vitamin D in children causes
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rickets -- a disease resulting from reduced mineralization of the bone matrix
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osteomalacia
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a softening of bones as a result of calcium depletion
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____ is necessary for collagen synthesis by osteoblast
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vitamin C
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vitamin C deficancy results in
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bones and cartilage that are deficient in collagen because collagen synthesis is impaired and can result in scurvy
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scurvy
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marked by ulceration and hemorrhage in almost any area of the body because of a lack of normal collagen sythesis in connective tissues
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growth hormone
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from anterior pituitary increases general tissue growth including overall bone growth by stimulating intersitial cartilage growth and apposistional bone growth
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thyroid hormone
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required for normal growth of all tissues including cartilage--decrease in hormone can result in decrease in size of individual
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sex hormone
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can influence bone growth. decreased levels of testosterone or estrogen can prolong the growth pase of the epiphyseal plates
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bone remodeling converts ____ into ____
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woven bone
lamellar bone |
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bone has a mechanical advantage as a ____ rather than a ____
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cylinder
rod |
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the relative thickness of compact bone is maintained by
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the removal of bone on the inside by osteoclasts and the addition of bone to the out side by osteoblast
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basic multicellular unit (BMU)
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is a temporarry assembly of osteoclast and osteoblasts that travel through or across he surface of bone
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average life span of a BMU
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6 months
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BMU activity renews the entire skeleton
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every 10 years
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intersitial lamellae are
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remnants of osteons that were not completely removed when a BMU formed a tunnel
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