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64 Cards in this Set
- Front
- Back
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Bone tissue can be classified as either ____________ / __________ or _____/ _____/ _______
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compact / cortical or cancellous / trabecular / spongy
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What are the characteristics of compact bone?
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It is a dense solid mass
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What are the characteristics of cancellous bone?
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It is lattice like
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The shell of all bones is ________ bone
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compact
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The center of bones is __________ and contains __________
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cancellous/trabecular , marrow
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What percentage of the human skeleton is compact bone
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80%
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Define "diaphysis"
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The long cylindrical part of the bone. The shaft
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Define "epiphysis"
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The round end of the bone facing the joint cavity
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Define "metaphysis"
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the cone shaped portion in between the epiphysis and diaphysis
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What is the predominant structural make up of the diaphysis?
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Compact bone
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What is the predominant structural make up of the epiphysis?
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trabecular bone
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What is the predominant structural make up of the metaphysis?
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trabecular bone
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Define "periosteum" & identify where it is located.
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It is a fibrous connective tissue containing undifferentiated cells that covers the outer surface of most bones.
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What are "Sharpey's fibers" and what do they do?
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bundles of collagen fibers that emanate from the posterium and penetrate the bone matrix effectively anchoring the postereum to the bone
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What is endostiem and where is it found?
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It is a thin cellular layer and it is found in trabecular bone and the inner surface of the diaphysis facing the marrow cavity containing osteoprogenerator cells
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What type of cartilage is the epiphysis covered by?
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articular cartilage, a specialized hyaline cartilage.
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How does a developing long bone grow.
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It contains 1 or 2 growth plates (epiphyseal - metaphyseal complexes) about 90% trabecular bone, production and essentially all elongation takes place here.
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What is the epiphyseal - metaphyseal complex
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growth plate
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What is the growth plate replaced with in an adult?
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trabecular bone.
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Microscopically, bone can be classified in what ways?
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primary (immature, woven)
or secondary (mature, lamellar) |
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Where is Primary bone found?
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The embryo, select sites (eg. fractures) in adults, tooth sockets, and sutures of cranial bones.
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What are the physical characteristics of primary bone?
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It is temporary, the collagen fibers appear disorganized, and it contains more osteocytes and less minerals than secondary bone.
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What is the functional unit of compact bone?
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osteons, Haversian systems
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What is the functional unit of trabecular bone?
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trabecular packets
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What are the physical characteristics of Osteons?
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They are cylinders of concentrically arranged lamellae of collagen fibers (3-7 um). The innermost canal forms an Haversion canal (30-70 um) which contains nutrient vessels, nerves & connective tissue.
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Describe the structure of lamellae in Osteons?
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They are arranged parrallel to each other but at a slightly different pitch than adjacent lamellae. This arrangement provides great strength to bone.
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What is the predominant cell type found in mature bone? Where are
they? |
Osteocytes
trapped in lacunea |
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How do the osteocytes of
adjacent lacunae interact |
By cell processes that extend
through bone via canaliculi (small canals) |
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What is a cement line? Where is it found?
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A cement line (1-2 um),
which is mineralized matrix deficient in collagen, is found at the edge of the outermost lamella. |
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Where can Interstitial lamellae be found?
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Interstitial lamellae can be found between
osteons. They are remnants of older osteons. |
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Where can Inner and outer
circumferential lamellae be found? |
Inner and outer
circumferential lamellae are located adjacent to the marrow cavity and to the periosteum, respectively |
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How are Haversian canals connected, and to what are they connected to?
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Haversian canals are connected to
each other, to the marrow cavity, and to the periosteum by Volkmann's canals, which run roughly perpendicularly to the Haversian canals. |
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What are Volkmann's canals
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Haversian canals are connected to
each other, to the marrow cavity, and to the periosteum by Volkmann's canals, which run roughly perpendicularly to the Haversian canals. |
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What are the characteristics of trabecular packets?
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a. They are typically crescent shaped
b. Most are smaller than osteons (less than 200 um) c. They contain no blood vessels. d. The shape of their lamellae reflects that of the packet (triangular). e. Several trabecular packets can be held together by a cement line. f. *Exception = Some are large and have an osteon-like structure including a central blood vessel. |
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Where are osteocytes housed in trabecular bone?
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In lacunae along lamellae
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How do osteocytes communicate with each other in trabecular packets?
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They communicate with each other through cell processes housed in canaliculi
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How does trabecular bone receive nutrients?
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The bone receives its nutrients by diffusion through canaliculi that reach the surface of the packet so inner rings less readily supplied.
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What is the Composition of bone?
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24% organic (90% collagen)
76% inorganic |
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What inorganic substances are present in bone? (name 6)
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a) ***Hydroxyapatite (calcium phosphate crystal)
b) Bicarbonate c) Citrate d) Magnesium e) Potassium f) Sodium |
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What makes up the organic portions of the bone matrix?
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a) 90% of the organic material is collagen
b) the collagen is primarily type 1 collagen which contains one alpha-2 chain and 2 alpha-1 chains. |
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What brings about the hardness and rigidity of bone? How is it arranged?
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a) Hydroxyapatite (Ca10(PO4)6(OH)2) interacts with collagen and noncollagenous proteins.
b) It is arranged in needles, plates, or leaves |
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What are the different types of bone cells? (4)
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a) Osteoprogenitor cells (mesenchymal cells & hematopoietic stem cells)
b) Osteoblasts c) Osteocytes d) Osteoclasts |
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What do Osteoblasts secrete? (3)
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*Contain a lot of RER
a) Osteoid - which is unmineralized bone matrix (mostly type I collagen) b) alkaline phosphatase – aides in the mineralization of bone c) other proteins – osteocalcin, osteonectin, and osteopontin. |
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How are Osteoblasts regulated?
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They are regulated by and contain receptors for parathyroid hormone (PTH) and vitamin D.
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Osteoblasts are derived from ___________ cells.
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mesenchymal cells.
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How do osteocytes develop?
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As the osteoblasts become surrounded by osteoid, which eventually mineralizes, they differentiate into osteocytes.
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What is the principal cell of mature bone? What is its function?
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a) Osteocytes
b) Maintain and monitor the status of bone |
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How do osteocytes accomplish intercellular communication?
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Gap junctions at the end of the osteocytes' cell processes permit intercellular communication through canaliculi.
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What is the function of Osteoclasts
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They are cells that resorb bone.
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What are the characteristics of osteoclasts?
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a) multinucleated giant cells (can be 50 nuclei)
b) located in cavities on the surface of bone. c) The cell surface facing bone is called the ruffled border. It is the site of bone resorption. d) Contain a lot of mitochondria |
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How do osteoclasts resorb bone?
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a) A proton ATPase on the plasma membrane lowers the pH of the resorption cavity.
b) The low pH contributes to the solubilization of the hydroxyapatite. c) The low pH maintains the optimum activity for proteases (collagenases, metalloproteinases, cystiene proteinases, phosphatases). |
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How osteoclast activity regulated locally so that is does not countinuously dissolve bone?
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There is TGF-beta present in the bone and as the osteoclast dissolves the matrix it releases TGF-beta, which is a negative regulator for osteoclast activity.
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What happens to the dissolved matrix as a result of osteoclast activity?
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There is a transcytotic vesicle that carries the degraded material from the howship’s lacunae to the opposite surface to be released.
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What is the howship's lacunae
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The cavity created by the osteoclast during bone resorption
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How do osteoclasts attach to bone for the purpose of resorption? What does it create?
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a) RGB Integrin attaches the cell to the bone creating a sealing zone that seals off the howship’s lacunae from the rest of the ECM.
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How does calcitonin effect osteoclast activity?
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Osteoclasts display receptors for calcitonin on their cell surface.
Calcitonin inhibits bone resorption. (not as powerful as PTH) |
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Osteoclasts are derived from __________ stem cells
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hematopoietic (aka blood monocytes, related to the mononuclear phagocyte series)
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Where are Noncollagenous proteins are found in bone?
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In the ground substance of bone.
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What roles do non-collagenous proteins play pertaining to bone? (5)
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a) Signal transducers
b) Mineralization c) Cell-matrix interactions d) Firbril formation e) Markers |
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Name the non-collagenous proteins (6)
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a) Osteocalcin
b) Osteonectin c) Bone sialoprotein d) Osteopontin e) Decorin f) bone morphogenetic proteins |
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What is Osteocalcin and what does it do (2)?
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a) It is a bone glycoprotein
b) promotes calcification by binding calcium via its gamma-carboxyglutamic acid residues. (the glutamic acid has 2 carboxylic side chains instead of one, 2 neg charges for the 2 positive charges of calcium) c) binds hydroxyapatite via gamma-carboxyglutamic acid d) It attracts bone resorbing cells |
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What cell produces osteocalcin?
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Osteoblasts produce osteocalcin, which is clinically diagnostic for osteoblast function and active bone remodeling.
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What is Osteopontin and what does it do?
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a) It is a phosphorylated glycoprotein found in osteoid and at the mineralization front.
b) Helps to link the osteoclast to the surface of bone via inegrins c) Plays a role in mineralization, resorption, and is a signaling molecule. |
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What cells produce osteopontin?
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Made mostly by osteoblasts but also by Several types of cells, including osteoclasts,
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