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72 Cards in this Set
- Front
- Back
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Name the 5 functions of bone.
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1) Maintain shape of the body
2) Protect soft tissues 3) Provide framework for bone marrow 4) Transmit the force of muscle contraction 5) Serve as reservoir for ions, especially calcium |
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Compact Bone
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-AKA cortical bone
-Dense, solid mass -Makes up the shell of all bones -~80% of human skeleton is compact |
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Cancellous Bone
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-AKA trabecular or spongy
-Lattice-like -Center of bones--contains marrow |
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Diaphysis
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In long bone, the long, cylindrical part of the bone
-Mostly compact bone |
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Epiphysis
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In long bone, the round end of the bone that faces the joint cavity
-Mostly trabecular bone |
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Metaphysis
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In long bone, this is cone-shaped
-Found between the epiphysis and the diaphysis -Mostly trabecular bone |
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Periosteum
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Fibrous CT containing undifferentiated cells
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Sharpey's Fibers
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-bundles of collagen fibers that emante from periosteum and penetrate the bone matrix.
-Serve as anchor for periosteum to bone |
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Endosteum
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Thin cellular layer of CT that lines the inner surface of the diaphysis facing the marrow cavity and the surface of trabecular bone
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Articular cartilage
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A specialized hyaline cartilage that covers the epiphyses
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Growth plates
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Epiphyseal-metaphyseal complexes in developing long bone where ~90% of tribecular bone production occurs and essentially all bone elongation occurs.
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What replaces the growth plate in adults?
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trabecular bone
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Describe primary bone
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-immature, woven
-Temporary -Found in the embryo and at select sites in adults (e.g. fractures) -Usually placed by secondary bone, except in tooth sockets and in sutures of cranial bones |
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What is the appearance of collagen fibers in primary bone vs secondary bone?
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Primary-Appear disorganized
Secondary-have a regular pattern |
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Describe secondary bone
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-mature, lamellar
-Regular pattern of collagen fibers |
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How does the cell density and mineral content of primary and secondary bone differ?
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Primary bone contains MORE osteocytes and has LESS mineral content than secondary bone
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What are osteons?
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-Also known as Haversian systems
-functional units in compact bone -Cylinders of concentrically arranged lamellae |
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What are lamellae?
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concentric arrangement of cylinders made of collagen fibers in osteons
-3-7 microns in diameter? |
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What is a Haversian canal?
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The innermost lamellae in an osteon
-About 30-70 microns in diameter -Contains nutrient vessels, nerves, and CT |
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How does the arrangement of collagen fibers in lamellae provide great strength to bone?
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Arranged parallel to each other, but have a pitch different from that of fibers in adjacent lamellae
-Resembles plywood |
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What are lacunae?
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Cavities within the lamellae that contain osteocytes
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What is the purpose of the canaliculi
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-They are small canals in bone that the cell processes of osteocytes extend through to interact with adjacent lacunae
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Where is the cement line located?
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-At the edge of the outermost lamella
-About 1-2 microns thick -Made of a mineralized matrix deficient in collagen |
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Where are interstitial lamellae located and where did they come from?
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Found between osteons
-They are remnants of older osteons |
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Where is the inner circumferential lamellae located?
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adjacent to the marrow cavity
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Where is the outer circumferential lamellae located?
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adjacent to the periosteum
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What is the purpose of the Volkmann's canals?
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Connect the Haversian canals to each other, to the marrow cavity, and to the periosteum
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How are the Volkmann's canals situated in bone?
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Run roughly perpendicularly to the Haversian canals
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How do the functional units of compact bone differ from those of trabecular bone?
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Trabecular packets are crescent shaped, are smaller than osteons, and contain no blood vessels
-Shape of lamellae reflects shape of packet |
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What are lacunae?
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Cavities within the lamellae that contain osteocytes
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What is the purpose of the canaliculi
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-They are small canals in bone that the cell processes of osteocytes extend through to interact with adjacent lacunae
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Where is the cement line located?
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-At the edge of the outermost lamella
-About 1-2 microns thick -Made of a mineralized matrix deficient in collagen |
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Where are interstitial lamellae located and where did they come from?
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Found between osteons
-They are remnants of older osteons |
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Where is the inner circumferential lamellae located?
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adjacent to the marrow cavity
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Where is the outer circumferential lamellae located?
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adjacent to the periosteum
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What is the purpose of the Volkmann's canals?
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Connect the Haversian canals to each other, to the marrow cavity, and to the periosteum
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How are the Volkmann's canals situated in bone?
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Run roughly perpendicularly to the Haversian canals
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How do the functional units of compact bone differ from those of trabecular bone?
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Trabecular packets are crescent shaped, are smaller than osteons, and contain no blood vessels
-Shape of lamellae reflects shape of packet |
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Do the lamellae in trabecular bone contain osteocytes?
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Yes, they communicate with each other through cell processes housed in canaliculi
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How does trabecular bone receive its nutrients?
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By diffusion through canaliculi that reach the surface of the packet.
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T/F: Only one trabecular packet is held together by a cement line
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False-several trabecular packets can be held together by a cement line.
Additional info: Some trabecular packets are large and have an osteon-like structure including a central blood vessel. |
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T/F: Bone is highly vascularized but not innervated
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False-Bone is both highly vascularized and innervated. Blood vessels penetrate the epiphyses and metaphyses. Haversian canals, periosteum, and medullary vessels are innervated.
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How much of bone is composed of organic material?
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20%
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What makes up the majority of organic material in bone?
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Collagen (90%)
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What is the main type of collagen in bone?
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Type 1, which contains one alpha-2 chain and two alpha-1 chains.
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What comprises the amorphous ground substance in bone?
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Noncollagenous proteins which play roles in fibrillogenesis and mineralization
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How is Hydroxyapatite important to bone?
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Interacts with collagen and noncollagenous proteins to bring about hardness and rigidity
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What is Hydroxyapatite composed of?
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Calcium, Phosphate, and Hydroxide
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What other minerals are found in bone?
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Bicarbonate, citrate, magnesium, potassium, and sodium
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What are osteoprogenitor cells?
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Two types of mitotically active cells that differentiate into either osteoblasts or osteoclasts
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What are osteoblasts?
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bone forming cells that secrete osteoid
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What is osteoid?
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Unmineralized bone matrix secreted by osteoblasts
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What is secreted by osteoblasts?
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Osteoid-unmineralized bone matrix
-Alakline phosphatase-protein that aids in mineralization of bone -Type I collagen -Noncollagenous bone proteins: osteocalcin, osteonectin, and osteopontin |
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How do the noncollagenous bone proteins secreted by osteoblasts play a role in bone formation?
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Osteocalcin, osteonectin, and osteopontin participate in calcification and regulate the calcium and phosphate content of bone
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How are osteoblasts regulated?
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have receptors for parathyroid hormone and vitamin D
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Where are osteoblasts derived from?
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Mesenchymal cells
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What are osteocytes?
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Osteoblasts that have differentiated after they have become surrounded by osteoid
-Principal cells of mature bone |
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How do osteocytes communicated with each other?
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Through gap junctions at the end of the osteocytes' cell processes
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What is the role of osteoclasts?
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Bone resorption
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Where are osteoclasts located?
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They are multinucleated giant cells that are located in the cavities on the surface of bone
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What is the ruffled border?
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The cell surface facing bone which serves as the site of bone resorption
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How does pH relate to bone resorption?
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low pH in the resorption cavity contributes to the solubilization of the mineral phase. The low pH is maintained by a proton ATPase on the plasma membrane
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How are osteoclasts regulated?
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Display receptors for calcitonin on their cell surface
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What is calcitonins effect on bone resorption?
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inhibits
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Where are osteoclasts derived from?
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Hematopoietic stem cells related to the mononuclear phagocyte series.
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Where are noncollagenous proteins found and what is their role in bone?
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In the ground substance.
Play important roels in synthesis and turnover of bone |
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What is osteocalcin?
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Noncollagneous protein, bone glycoprotein that promote calcification by binding caclium via its gamma-carboxyglutamic acid residues
-Produced by osteoblasts -Presence of osteocalcin is clinically diagnostic for osteoblast function and active bone remodeling -Osteocalcin also attract bone resorbing cells |
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What is osteonectin (SPARC)?
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-Noncollagenous glycoprotein that binds calcium, hydroxyapatite and collagen.
-May play a role in mineralization, assembly of fibrillar network of collagens, and in the regulation of cell growth. -Produced by many cell types, including bone cells |
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What is bone sialoprotein?
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Noncollagenous protein
-Binds calcium, promotes mineralization, and anchors osteoclasts to surface of bone -Synthesized by osteoblasts and osteoclasts and is found in osteoid, especially at the mineralization front |
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What is osteopontin?
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Phosphorylated glycoprotein found in osteoid and at mineralization front. May promote attachment of bone cells to bone matrix and act as a signaling molecule.
-Secreted by many types of cells, including osteoblasts and osteoclasts. |
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What is Decorin?
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Noncollagenous protein
-Small proteoglycan that regulates collagen formation by binding to type I and II collagen and inhibiting fibrillogenesis -May also regulate cell proliferation |
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What are bone morphogenetic proteins and how many are there?
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7 (BMPs 1-7)
-Act as differentiation factors and are involved in development of nearly all organs and tissues. -Also involved in maintaining and repairing bone |
