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Ch 6 Bones and Bone Tissue

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Terms in this set (20)

  • Major functions of the skeleton

    Protection, mineral storage (Ca, P, Mg), hematopoiesis (blood cell formation), movement, support, fat storage, and hormone production.

  • Classification of bones by shape

    Long bones (longer than wide), short bones (about as long as wide), flat bones (broad, flat, thin), irregular bones (shape does not fit other classes), and sesamoid bones (round, flat bones found within tendons).

  • Structure of a long bone

    Includes epiphysis (ends), diaphysis (shaft), periosteum (outer fibrous and osteogenic layers), articular cartilage, nutrient foramina, endosteum, medullary cavity, compact bone, and spongy (cancellous) bone.

  • Periosteum composition and function

    Outer dense irregular collagenous layer and inner osteogenic layer; collagen fibers extend into bone matrix as perforating fibers, providing attachment and bone growth/repair.

  • Bone marrow types and functions

    Red marrow: hematopoietic stem cell niche, highly vascularized. Yellow marrow: fat storage, also vascularized. Composition changes with age.

  • Bone matrix composition

    Inorganic matrix: mostly hydroxyapatite (calcium phosphate), provides compression resistance. Organic matrix (osteoid): mostly collagen and glycosaminoglycans (GAGs), provides tensile strength.

  • Effects of removing organic or inorganic matrix from bone

    Removing organic matrix (collagen) makes bone brittle and prone to shattering. Removing inorganic matrix (minerals) makes bone unable to resist compression.

  • Rickets and osteogenesis imperfecta

    Rickets: calcium deficiency causing soft, deformed bones. Osteogenesis imperfecta: collagen defect causing brittle bones.

  • Osteogenic cells

    Mesenchymal stem cells in periosteum and endosteum that differentiate into osteoblasts; important for fracture repair.

  • Osteoblasts

    Bone-forming cells found in inner periosteum and endosteum; secrete collagen, osteocalcin, calcium, and phosphate to form osteoid that mineralizes into bone.

  • Osteocytes

    Mature osteoblasts trapped in lacunae within bone matrix; over 90% of bone cells; have dendritic processes in canaliculi for sensing strain and cell communication.

  • Osteoclasts

    Multinucleated cells from bone marrow that resorb bone by secreting H+ ions and enzymes; release minerals into bloodstream.

  • Compact bone structure

    Organized into osteons (Haversian systems) with concentric lamellae around central canals; osteocytes in lacunae connected by canaliculi; perforating (Volkmann) canals connect osteons.

  • Lamellae in bone

    Rings of collagen fibers in bone matrix; collagen fibers alternate orientation between lamellae to increase strength.

  • Spongy (trabecular) bone structure

    Composed of trabeculae (rod or plate-like structures) with concentric lamellae but no osteons or canals; helps distribute stress efficiently.

  • Intramembranous ossification

    Bone formation within mesenchymal membrane; mesenchymal stem cells differentiate into osteoblasts forming osteoid; forms skull and clavicles.

  • Endochondral ossification

    Bone formation within hyaline cartilage scaffold; chondrocytes die, cartilage calcifies, osteoblasts form bone collar and spongy bone; forms most other bones.

  • Longitudinal vs appositional bone growth

    Longitudinal growth: lengthening at epiphyseal plate, stops after adolescence. Appositional growth: width growth by bone deposition under periosteum, continues throughout life.

  • Wolff's Law of Bone

    Bone architecture adapts to mechanical stresses placed on it; bone mass and density increase in response to greater load.

  • Bone remodeling

    Continuous process replacing about 10% of bone per year; balances bone resorption by osteoclasts and formation by osteoblasts to maintain strength and mineral homeostasis.