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Skeletal System Notes Anatomy

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Skeletal System Notes Anatomy Powered By Docstoc
					                               Bones and Skeletal Tissues
 Cartilage: our skeleton is initially made of cartilage but most of it is replaced by bone.
   Chondrocytes: cartilage cells found in lacunae, matrix made of ground substances
     and fibers
   Hyaline: support w/flexibility and resilience. Most abundant skeletal cartilage;
     covers bone ends at joints, connects ribs to sternum, larynx (voice box), trachea,
     external nose
   Elastic: bending and stretching; external ear, epiglottis
   Fibrocartilate: compressible, great tensile strength; knee, vertebral disks
   Cartilage growth
      Appositional: expands cartilage from external side
      Interstitial: expands cartilage from within
 Bones
   Functions:
      Support: limbs act as pillars, rib cage
      Protection: skull, vertebrae, rib cage
      Movement: muscles attached to the bone by tendons
      Mineral Storage: calcium, phosphate
      Blood cell formation: hematopoeisis (in bone marrow)
   Bone Classification:
      Dense ourter smooth later = compact bone
      Honeycomb of trabeculae (needle like pieces)= spongy bone
      Long bones: longer than wide; limbs
      Short bones: cubelike; wrist, ankles
           Sesamoid bone-embeded with in tendon; patella
      Flat bones: thin, flat, curved; sternum, ribs, skull
      Irregular bones: vertebrae, hips
   Structure:
      Gross anatomy:
           Long bones:
               Diaphysis- tubelike shaft; compact bone around yellow bone marrow
                  cavity fat
               Epiphyses- bone ends; exterior is compact bone, interior is spongy;
                  joint surfaces have articular cartilage
           Membranes:
               Periosteum-external, covers diaphysis
                   Osteoblasts- make bone
                   Osteoclasts- break down bone
                   Osteocytes-mature bone cells
                   Sharbey’s fibers: collagen fivers that extend from fibrous layer into
                      bone matrix
               Endosteum: covers trabeculae of cpony bone, lines canals in compact
                  bone (internal)
                   Short, Irregular, and Flat bones-thin plates of compact bone on
                      outside, spongy bone within.
                       Not cylindrical-rib shaft, no epiphyses
                      Have bone marrow but no marrow cavity
                      internal layer of spongy bone = diploe
          Red Marrow: found in cavities of spongy bone in compact bones and
             diploe of flat bones.
              In adults, hematopoiesis usually occurs in head of femur and humerus
   Microscopic Anatomy (histology):
      Compact bone: arranged in haverstian systems (osteons)
          Matrix tubes called lamella (rings
          Haversian (central) canal in middle of osteon contains blood vesels and
             nerves
          Volkman’s canals occur at right angles
          Osteocytes are in lacunae; canaliculi connect lacunae
      Spongy bone: made of trabeculae, looks poorly organized at first glance; no
         osteons
          Bone struts; lamellae and osteocytes connected by canaliculi
 Chemical composition of bone:
   Organic: cells (osteoblasts, osteocytes, & osteoclasts) and osteoid (matrix) of
     collagen fibers
   Inorganic: (65%) hydroxyapaties (mineral salts), calcium phosphates-crystals in
     extracellular matrix
 Bone markings:
   External surfaces of bones have bulges, depressions, and holes where muscles,
     ligaments, and tendons attach, as well as blood vessels and nerves enter, some
     help form joints
 Bone Development: osteogenesis, ossification
   Intremembranes: skull, clavicles, flat bones, steps involve formations of
     ossification center bone matrix woven bone and periosteum compact bone
     plats and red marrow = 8th week of development
   Endochondrial: uses hyaline cargilage as model; bone collar forms around
     diaphysis of hyaline cargilagecartilage in center calcifiesperiosteal bud
     invades cavities, spongy bone formsmedullary cavity formsepiphyses ossify
     = 2nd month of development
   Epiphyseal plates- growth plates
   Postnatal bone growth:
      Infancy and youth- long bones lengthen at epiphyseal plates, bones also grow
         in thickness; hormones regulate
      Adolescence/adulthood- bones stop growing except for facial bones
      Epiphyseal plate closure happens at age 18 in females and 21 in males