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Biology ch 6
| Question | Answer |
|---|---|
| Skeletal System Functions | Support Protection Movement Storage Blood Cell Production |
| •Support | Bone is hard and rigid; cartilage is flexible yet strong. Cartilage in nose, external ear, thoracic cage and trachea. Ligaments- bone to bone |
| •Protection | Skull around brain; ribs, sternum, vertebrae protect organs of thoracic cavity |
| •Movement | Produced by muscles on bones, via tendons. Ligaments allow some movement between bones but prevent excessive movement |
| •Storage | Ca and P. Stored then released as needed. Fat stored in marrow cavities |
| •Blood cell production | Bone marrow that gives rise to blood cells and platelets (RBC) |
| Components of Skeletal System | •Bone •Cartilage |
| •Cartilage | three types: No blood supply –Hyaline –Fibrocartilage –Elastic |
| –Hyaline | Ends of bones: articular cartilage; gives rise to bone |
| –Fibrocartilage | pelvic bone |
| –Elastic | Ear; Epiglottis |
| Hyaline Cartilage | •Consists of specialized cells that produce matrix |
| –Chondroblasts | form matrix |
| –Chondrocytes | surrounded by matrix; are lacunae |
| •Matrix | Collagen fibers for strength, proteoglycans for resiliency |
| •Perichondrium | Double-layered C.T. sheath. Covers cartilage except at articulations |
| –Inner Perichondrium | More delicate, has fewer fibers, contains chondroblasts |
| –Outer Perichondrium | Blood vessels and nerves penetrate. No blood vessels in cartilage itself |
| •Articular cartilage | Covers bones at joints; has no perichondrium (Also known as hyaline cartilage) |
| •Growth | –Appositional –Interstitial |
| –Appositional | New chondrocytes and new matrix at the periphery |
| –Interstitial | Chondrocytes within the tissue divide and add more matrix between the cells. |
| •Diaphysis | –Shaft –Compact bone |
| •Epiphysis | –End of the bone –Cancellous bone |
| •Epiphyseal plate | growth plate |
| –Hyaline cartilage | present until growth stops |
| •Epiphyseal line | bone stops growing in length |
| •Medullary cavity | In children medullary cavity is red marrow, gradually changes to yellow in limb bones and skull (except for epiphyses of long bones). Rest of skeleton is red. –Red marrow –Yellow marrow |
| •Periosteum | –Outer is fibrous –Inner is single layer of bone cells including osteoblasts, osteoclasts and osteochondral progenitor cells |
| •Periosteum | –Fibers of tendon become continuous with fibers of periosteum. |
| –Sharpey’s fibers | some periosteal fibers penetrate through the periosteum and into the bone. Strengthen attachment of tendon to bone. |
| •Endosteum | Similar to inner layer of periosteum. Lines all internal spaces including spaces in cancellous bone. |
| •Bone matrix | Like reinforced concrete. Rebar is collagen fibers, cement is hydroxyapetite |
| –Organic | collagen and proteoglycans |
| –Inorganic | hydroxyapetite. CaPO4 crystals |
| •Bone cells | –Osteoblasts –Osteocytes –Osteoclasts |
| –Stem cells or osteochondral | progenitor cells |
| •Woven bone | collagen fibers randomly oriented |
| •Lamellar bone | mature bone in sheets |
| •Cancellous bone | trabeculae (red bone marrow located here) |
| •Compact bone | dense |
| •If mineral removed | bone is too bendable |
| •If collagen removed | bone is too brittle |
| •Osteoblasts | –Formation of bone through ossification or osteogenesis. Collagen produced by E.R. and golgi. Released by exocytosis. Precursors of hydroxyapetite stored in vesicles, then released by exocytosis. |
| –Ossification | formation of bone by osteoblasts. Osteoblasts communicate through gap junctions. Cells surround themselves by matrix. |
| •Osteocytes | Mature bone cells. Stellate. Surrounded by matrix, but can make small amounts of matrix to maintain it. |
| –Lacunae | spaces occupied by osteocyte cell body |
| –Canaliculi | canals occupied by osteocyte cell processes –Nutrients diffuse through tiny amount of liquid surrounding cell and filling lacunae and canaliculi. Then can transfer nutrients from one cell to the next through gap junctions. |
| •Osteoclasts | Resorption of bone –Release enzymes that digest the bone. –Derived from monocytes (which are formed from stem cells in red bone marrow) –Multinucleated and probably arise from fusion of a number of cells |
| –Ruffled border | where cell membrane borders bone and resorption is taking place. |
| –H ions | pumped across membrane, acid forms, eats away bone. |
| •Stem Cells | Mesenchyme (Osteochondral Progenitor Cells) become chondroblasts or osteoblasts. |
| •Woven bone | Collagen fibers randomly oriented. |
| –Woven bone is formed | •During fetal development •During fracture repair •Remodeling –Removing old bone and adding new –Woven bone is remodeled into lamellar bone |
| –Lamellae | Mature bone in sheets is called Fibers are oriented in one direction in each layer, but in different directions in different layers for strength. |
| Cancellous (Spongy) Bone | •Trabeculae –Spaces filled with marrow. –Covered with endosteum. –Oriented along stress lines |
| •Trabeculae | interconnecting rods or plates of bone. Like scaffolding. |
| •Central or Haversian canals | parallel to long axis |
| •Lamellae | concentric, circumferential, interstitial |
| •Osteon or Haversian system | central canal, contents, associated concentric lamellae and osteocytes |
| •Perforating or Volkmann’s canal | perpendicular to long axis. Both perforating and central canals contain blood vessels. Direct flow of nutrients from vessels through cell processes of osteoblasts and from one cell to the next. |
| •Osteons (Haversian systems) | –Blood vessel-filled central canal (Haversian canal) –Concentric lamellae of bone surround central canal –Lacunae and canaliculi contain osteocytes and fluid |
| •Circumferential lamellae | on the periphery of a bone |
| •Interstitial lamellae between osteons. | Remnants of osteons replaced through remodeling |
| Circulation in Bone | •Perforating canals •Vessels of the central canal |
| •Perforating canals | blood vessels from periosteum penetrate bone |
| •Nutrients and wastes travel to and from osteocytes via | –Interstitial fluid of lacunae and canaliculi –From osteocyte to osteocyte by gap junctions |
| •Closure of epiphyseal plate | epiphyseal plate is ossified becoming the epiphyseal line. Between 12 and 25 years of age |
| •Articular cartilage | does not ossify, and persists through life |
| Growth at Articular Cartilage | •Increases size of bones with no epiphyses: e.g., short bones •Increases size of bones with no epiphyses: e.g., short bones |
| Factors Affecting Bone Growth | •Size and shape of a bone determined genetically but can be modified and influenced by nutrition and hormones |
| Factors Affecting Bone Growth | •Nutrition –Lack of calcium, protein and other nutrients during growth and development can cause bones to be small |
| –Vitamin D | •Necessary for absorption of calcium from intestines •Can be eaten or manufactured in the body |
| •Rickets | lack of vitamin D during childhood |
| •Osteomalacia | lack of vitamin D during adulthood leading to softening of bones |
| –Vitamin C | •Necessary for collagen synthesis by osteoblasts |
| •Scurvy | deficiency of vitamin C |
| •Lack of vitamin C | also causes wounds not to heal, teeth to fall out |
| •Hormones | –Growth hormone from anterior pituitary. Stimulates interstitial cartilage growth and appositional bone growth –Thyroid hormone required for growth of all tissues |
| Hormones | –Sex hormones such as estrogen and testosterone •Cause growth at puberty, but also cause closure of the epiphyseal plates and the cessation of growth |
| •Hematoma formation. | Localized mass of blood released from blood vessels but confined within an organ or space. Clot formation. |
| •Callus formation. Callus | mass of tissue that forms at a fracture site and connects the broken ends of the bone. |
| –Internal | blood vessels grow into clot in hematoma. |
| •Macrophages | clean up debris, osteoclasts break down dead tissue, fibroblasts produce collagen and granulation tissue. |
| •Chondroblasts from osteochondral | progenitor cells of periosteum and endosteum produce cartilage within the collagen. |
| •Osteoblasts invade. | New bone is formed. |
| –External- collar around opposing ends. | Periosteal osteochondral progenitor cells osteoblasts and chondroblasts. Bone/cartilage collar stabilizes two pieces. |
| •Callus ossification | Callus replaced by woven, cancellous bone |
| Bone remodeling | Replacement of cancellous bone and damaged material by compact bone. Sculpting of site by osteoclasts |
| Calcium Homeostasis | •Bone is major storage site for calcium •The level of calcium in the blood depends upon movement of calcium into or out of bone. –Calcium enters bone when osteoblasts create new bone; calcium leaves bone when osteoclasts break down bone |
| Calcium Homeostasis | –Two hormones control blood calcium levels- parathyroid hormone and calcitonin. |
| Effects of Aging on Skeletal System | •Bone matrix decreases. More brittle due to lack of collagen; but also less hydroxyapetite. •Bone mass decreases. Highest around 30. Men denser due to testosterone and greater weight. |
| Effects of Aging on Skeletal System | African Americans and Hispanics have higher bone masses than Caucasians and Asians. Rate of bone loss increases 10 fold after menopause. Cancellous bone lost first, then compact. • Increased bone fractures |
| •Bone loss causes | deformity, loss of height, pain, stiffness –Stooped posture –Loss of teeth |
| •Open (compound) | bone break with open wound. Bone may be sticking out of wound. |
| •Closed (simple) | Skin not perforated. |
| •Incomplete | doesn’t extend across the bone. Complete- does |
| •Greenstick | incomplete fracture that occurs on the convex side of the curve of a bone |
| •Hairline | incomplete where two sections of bone do not separate. Common in skull fractures |
| •Comminuted fractures | complete with break into more than two pieces |
| •Impacted fractures | one fragment is driven into the cancellous portion of the other fragment. |
| Impacted Fractures | • Classified on basis of direction of fracture •Linear •Transverse •Spiral •Oblique |
| •Dentate | rough, toothed, broken ends |
| •Stellate | radiating out from a central point. |
Created by:
Wendy Starks
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