Ch. 6- Skeletal System: Bones and Bone Tissue
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102 terms
Terms | Definitions |
|---|---|
 Ligament | are strong bands of fibrous connective tissue that attach to bones and hold them together. Connect bone to bone. |
| Tendon | Strong bands of connective tissue. Connect muscles to bone. |
| Chondroblasts | Produce a matrix surrounding themselves; Cartilage producing a cell/ matrix. |
| Chondrocyte | Mature cartilage cell. |
| Lacunae | Small space or cavity; potential space within the matrix of bone or cartilage normally occupied by a cell |
| Perichondrium | is a double-layered connective tissue sheath covering most cartilage. |
| Articular Cartilage | is the cartilage covering the ends of bones where they come together to form joints, has no perichondrium, blood vessels, or nerves. Within joints, the end of a long bone is covered with hyaline cartilage. |
| appositional growth | Chondroblasts in the perichondrium add new cartilage to the outside edge of the existing cartilage |
| interstitial growth | Chondrocytes within the tissue divide and add more matrix between the existing cells. |
| hydroxyapatite | The inorganic material of bone which is calcium phosphate crystal |
| Osteoblasts | form or create bone. |
| Matrix vesicles | membrane-bound sacs formed when the plasma membrane buds, or protrudes outward, and pinches off. |
| Ossification (osteogenesis) | is the formation of bone by osteoblasts. |
| Osteocyte | Mature bone cell surrounded by bone matrix. |
| Lacunae | The spaces occupied by the osteocyte cell bodies. |
| Canaliculi | The spaces occupied by the osteocyte cell processes. |
| Osteoclasts | are responsible for the reabsorption, or breakdown of bone. They are large cells with several nuclei |
| ruffled border | Where the plasma membrane of osteoclasts contacts bone matrix, it forms many projections. |
| Stem Cells | which can replicate and give rise to more specialized cell types. |
| Osteochondral Progenitor cells | are stem cells that can become osteoblasts or chondroblasts. They are located in the inner layer of the perichondrium and in layers of connective tissue that cover bone. |
| Woven bone | The collagen fibers are randomly oriented in many directions. |
| bone remodeling | The process of removing old bone and adding new bone. |
| Lamellar bone | is mature bone that is organized into thin sheets or layers approximately 3-7 micrometers (um) thick. |
| Lamellae | thin sheets or layers of bone. |
| Spongy bone | appears porous, has less bone matrix and more space than compact bone. It consists of interconnecting rods or plates of bone called trabeculae. |
| Trabeculae | interconnecting rods or plates of bone. |
| Compact bone | is denser and has fewer spaces than spongy bone. |
| Central canals | Vessels that run parallel to the long axis of the bone. They are lined with endosteum and contain blood vessels, nerves, and loose connective tissue. Also called harversian. |
| Concentric lamellae | are circular layers of bone matrix that surround a common center, the central canal. |
| Osteon | or haversian system, consists of a single central canal, its contents, and associated concentric lamellae and osteocytes. |
| Circumferential lamellae | are thin plates that extend around the bone. |
| interstitial lamellae | are remnants of concentric or circumferential lamellae that were partially removed during bone remodeling. |
| Perforating canals | run perpendicular to the long axis of the bone. Also known as volkmann canals. |
| Long bones | are longer than they are wide. Most of the bones of the upper and lower limbs are long bones. |
| Short bones | are round or nearly cube-shaped. ex) wrist and ankle bones. (carpals and tarsals). |
| Flat bones | have a relatively thin, flattened shape and are usually curved. ex) certain skull bones, ribs, breastbone (sternum), and shoulder blades (scapulae). |
| Irregular bones | have shapes that do not fit readily into the other 3 categories, such as the vertebrae, and facial bones. |
| diaphysis | shaft of a long bone. |
| epiphysis | Portion of a bone developed from a secondary ossification center and separated from the remainder of the bone by the epiphyseal plate. |
| epiphyseal Plate | or growth plate, separates the epiphysis from the diaphysis. Site at which bone growth in length occurs. Also called metaphysis or growth plate. |
| epiphyseal line | When bone stops growing in length, the epiphyseal plate becomes ossified. |
| Medullary cavity | Large, internal marrow-filled cavity/ space in the diaphysis of a long bone. |
| Red marrow | is the site of blood cell formation. |
| Yellow marrow | is mostly adipose tissue. |
| Periosteum | is a connective tissue membrane that that covers the outer surface of a bone. |
| Perforating fibers | Some collagen fibers of tendons and ligaments penetrate the periosteum into the outer part of the bone. Also called Sharpey fibers, they strengthen the attachment of the tendons or ligaments to the bone. |
| endosteum | is a single layer of cells that lines the internal surfaces of all cavities within bones, such as the medullary cavity of the diaphysis and the smaller cavities in spongy and compact bone. |
| Sinuses | air-filled spaces which are lined by mucous membranes. |
| intramembranous ossification | is a form of bone pattern during which bone is formed during fetal development. takes place in connective tissue membranes |
| endochondral ossification | is a form of bone pattern during which bone is formed during fetal development. takes place in cartilage. |
| Centers of ossification | The locations in the membrane where ossification begins. |
| fontanels | The larger, membrane-covered spaces between the developing skull bones that have not yet been ossified. |
| Cartilage Model | having the approximate shape of the bone that will later be formed. As the chondroblasts are surrounded by cartilage matrix, they become chondrocytes. It is surrounded by perichondrium, except where a joint will form connecting one to to another bone |
| bone collar | The osteoblasts produce compact bone on the surface of the cartilage model. |
| hypertrophy | enlarge |
| Calcified cartilage | The chondrocytes also release matrix vesicles, which initiate the formation of hydroxyapatite crystals in the cartilage matrix. The chondrocytes in the calcified area eventually die, leaving enlarged lacunae with thin walls of calcified matrix. |
| Primary ossification center | The osteoblasts produce bone on the surface of calcified cartilage, forming bone trabeculae, which changes the calcified cartilage of the diaphysis into spongy bone. |
| Secondary ossification center | In long bones, the diaphysis is the primary ossification center, and additional sites of ossification, appear in the epiphyses. |
| Zone of resting cartilage | is nearest the epiphysis and contains randomly arranged chondrocytes that do not divide rapidly. |
| Zone of Proliferation | Produce new cartilage through interstitial cartilage growth. The chondrocytes divide and form columns resembling stacks of plates or coins. |
| Zone of hypertrophy | The chondrocytes produced in the zone of proliferation mature and enlarge. Thus, a maturation gradient exists in each column: The cells nearer the epiphysis are younger and actively proliferating, whereas the cells progressively nearer the diaphysis are older and undergoing hypertrophy. |
| Zone of Calcification | is very thin and contains hypertrophied chondrocytes and calcified cartilage matrix. The hypertrophied chondrocytes die, and blood vessels from the diaphysis grow into the area. |
| Vitamin D | Fat-soluable vitamin produced from precursor molecules in skin exposed to ultraviolet light; increases calcium and phosphate uptake from the intestines. Is necessary for the normal absorption of calcium from the intestines. The body can either synthesize or ingest it. Its rate of synthesis increases when the skin is exposed to sunlight. |
| rickets | A disease resulting from reduced mineralization of the bone matrix. |
| Osteomalacia | A softening of the bones as a result of calcium depletion. |
| Vitamin C | is necessary for the collagen of synthesis by osteoblasts. |
| Scurvy | which is marked by ulceration and hemorrhage in almost any area of the body because normal collagen synthesis is not occurring in connective tissues. |
| Growth hormone | From the anterior pituitary increases general tissue growth, including overall bone growth, by stimulating interstitial cartilage growth and appositional bone growth. |
| Thyroid hormone | is also required for normal growth of all tissues, including cartilage; therefore, a decrease in this hormone can result in a smaller individual. |
| Sex hormone | also influence bone growth. Estrogen (a class of female sex hormones) and testosterone ( a male sex hormone) initially stimulate bone growth, which accounts for the burst of growth at puberty; when production of these hormones increases. |
| bone remodeling | is a process where bone that becomes old is replaced with new bone. |
| basic multicellular unit (BMU) | A temporary assembly of osteoclasts and osteoblasts that travels through or across the surface of bone, removing old bone matrix and replacing it with new bone matrix. |
| hematoma | is a localized mass of blood released from blood vessels but confined within an organ or space. |
| Callus | is a mass of tissue that forms at a fracture site and connects the broken ends of the bone. |
| internal callus | forms between the ends of the broken bone, as well as in the marrow cavity if the fracture occurs in the diaphysis of a long bone. |
| nonunion of the bone | the 2 ends of the bone do not rejoin. |
| external callus | forms a collar around the opposing ends of the bone fragments. Is a bone-cartilage collar that stabilizes the ends of the broken bone. |
| Parathyroid hormone (PTH) | Peptide hormone produced by the parathyroid gland; increases bone breakdown and blood calcium levels. |
| Calcitonin | hormone released from parafollicular cells that acts on tissues to cause a decrease in blood levels of calcium ions. Secreted from the thyroid gland when blood calcium levels are too high, decreases osteoclast activity by binding to receptors on the osteoclasts. |
| receptor for activation of nuclear factor kappaB ligand (RANKL). | is expressed on the surface of the osteoblasts and stem cells and can combine with RANK. |
| receptor for activation of nuclear factor kappaB (RANK) | found on the cell surfaces of osteoclast precursor cells. |
| Osteoprotegerin (OPG) | which is secreted by osteoblasts and stem cells. |
| Open fracture | (formally called compound) occurs when an open wound extends to the site of the fracture or when a fragment of the bone protrudes through the skin. |
| Closed fracture | if the skin is not proliferated. (formally called simple) |
| complicated fracture | If the soft tissues around a closed fracture are damaged. |
| Incomplete fracture | does not extend completely across the bone. |
| Complete fracture | is one in which the bone is broken into at least 2 fragments |
| greenstick fracture | An incomplete fracture that occurs on the convex side of the curve of the bone. |
| Hairline fracture | are incomplete fractures in which 2 sections of bone do not separate; are common in the skull. |
| comminuted fracture | is a complete fracture in which the bone breaks into more than 2 pieces - usually 2 major fragments and a smaller fragment. |
| impacted fracture | one fragment is driven into the spongy portion of the other fragment. |
| Linear fracture | run parallel to the long axis of the bone. |
| Transverse fracture | are at right angles to the long axis. |
| Spiral fracture | take a helical course around the bone. |
| oblique fracture | run obliquely in relation to the long axis. |
| Dentate fracture | have rough, toothed, broken ends. |
| Stellate fracture | have breakage lines radiating from a central point. |
| Osteoporosis | or porous bone, results from a reduction in the overall quality of bone tissue. It occurs when the rate of bone reabsorption exceeds the rate of bone formation. |
| hormone replacement therapy (HRT) | With estrogen decreases osteoclast numbers by inhibiting the production of RANKL. |
| Selective estrogen receptor modulators (SERMs) | A class of drugs that bind to estrogen receptors. These drugs may protect against bone loss without increasing the risk for breast cancer. |
| Statins | are drugs that inhibit cholesterol synthesis; they also stimulate osteoblast activity, and some evidence indicates that they can reduce the risk for fractures. |
| bisphosphonates | which concentrate in bone. When osteoclasts break down bone, the bisphosphonates are taken up by the osteoclasts. |
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