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14 Cards in this Set
- Front
- Back
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What is periosteum?
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-is a layer of noncalcified connective tissue covering bone on its external surfaces, except at synovial joints
-it is composed of an outer dense fibrous collagenous layer and an inner cellular osteoprogenitor (osteogenic) layer -sharpy fibers (type I collagen) attach the periosteum to the bone surface -the periosteum functions to distribute blood vessels to bone |
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What is endosteum?
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-is a thin specialized connective tissue that lines the marrow cavities and supplies osteoprogenitor cells and osteoblasts for bone growth & repair
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Describe the regions in a bone & whether they contain trabecular or cortical bone
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✦Diaphysis (shaft) – exclusively cortical bone surrounding a marrow cavity
✦Epiphysis at each end – mostly trabecular surrounded by thin shell of cortical bone ✦Metaphysis – between diaphysis and epiphysis – transition mostly cortical to mostly trabecular |
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Describe the blood supply of bone
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✦nutrient artery enters diaphysis to supply the marrow & cortical bone (enters through nutrient foramen)
✦metaphyseal arteries ✦epiphyseal arteries -vessel anastamose in mature bone except between epiphyseal and metaphyseal region |
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What is the bone matrix composed of?
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-type I collagen
-glycoproteins -hydroxapatite (mainly calcium & phosphorus) -organized in layers (lamellae) in mature bone --> lamellae occur at right angles to each other -disorganized in immature (woven) bone (often found in developing & healing bone) (not as strong) |
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Describe the appearance & function of osteoblasts:
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Osteo“B”lasts “B”uild bone
-round cells found on bone surfaces -derived from mesenchymal stem cells -secrete osteoid (mixture of bone matrix proteins) which then become mineralized -become osteocytes as they are embedded in the matrix they secrete |
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Describe the appearance & function of osteocytes:
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-small round cells surrounded by bone matrix
-posses fine processes extending into canaliculi -sense mechanical strain |
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Describe the appearance & function of bone lining cells:
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-flattened cells covering resting bone surfaces (in periosteum & endosteum)
-capable of differentiating into osteoblasts |
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Describe the appearance & function of osteoclasts:
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-large multinucleate cells
-derived from monocyte/macrophage linage -sparsely scattered on bone surfaces -responsible for bone resorption: -adhere to bone through sealing zone, creating microenvironment between cell and bone surface -secrete hydrogen ions and lysosomal enzymes to degrade bone matrix |
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Describe the organization of bone
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✦Trabecular bone
-network of bone spicules -interspersed with spaces containing bone marrow & blood vessels ✦Cortical bone -organized into Haversian systems (osteons) -osteons are long cylindrical structures that run approximately parallel to the long axis of the diaphysis -they are composed of 4-20 lamellae surrounding a central haversian canal, which contains blood vessels, nerves, and loose connective tissue. They are lined by osteoprogenitor cells and osteoblasts -they are often surrounded by an amorphous cementing substance -they are interconnected by Volkmann canals, which also connect to the periosteum and endosteum & carry the neurovascular supply -interstitial lamellae are irregularly shaped lamellae between haversian systems -they are remnants of remodeled haversian systems |
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What cells are found in cartilage?
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-chondrocytes – the only cells present in cartilage
-encased in lacunae within extracellular matrix -proliferation results in occasional pairs of chondrocytes within lacunae (‘interstitial growth’) |
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What makes up the extracellular matrix of cartilage?
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-type II collagen (almost exclusive to cartilage)
-amorphous extracellular material made up of proteoglycans and hyaluronan -proteoglycans are composed of core protein and sulphated glycosaminoglycans (GAG) side chains (polysaccharides) -proteoglycans form large aggregates with hyaluronan (a large GAG) -GAGs have multiple negative charges, therefore strongly hydrophilic -swelling pressure of hydrophilic proteoglycan aggregates counteracted by tension of collagen fibers, resulting in extremely high resistance to compression |
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What are the different types of cartilage & their differences?
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What is perichondrium?
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Perichondrium is a layer of dense irregular connective tissue which surrounds the cartilage of developing bone. It consists of two separate layers: an outer fibrous layer and inner chondrogenic layer. The fibrous layer contains fibroblasts, which produce collagenous fibers. The chondrogenic layer remains undifferentiated and can form chondroblasts or chondrocytes. Perichondrium can be found around the perimeter of elastic cartilage and hyaline cartilage. Fibrocartilage and articular cartilage both lack perichondrium.
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