Skeletal system

Cards (19)

  • Skeletal system
    Includes the varied bones of the skeleton and the cartilages, ligaments, and other connective tissues that stabilize or interconnect them
  • Divisions of the skeletal system
    • Axial skeleton (bones of the skull, vertebral column, sternum, and ribs)
    • Appendicular skeleton (bones of the limbs and the associated bones that connect the limbs to the trunk at the shoulders and pelvis)
  • Functions of the skeleton
    • Support
    • Storage of minerals
    • Blood cell production
    • Protection
    • Leverage
  • Bone structure
    Contains specialized cells and an extracellular matrix consisting of protein fibers and a ground substance
  • Bone matrix
    • Calcium phosphate (Ca3(PO4)2) accounts for almost two-thirds of the weight of bone, interacting with calcium hydroxide to form hydroxyapatite (Ca10(PO4)6(OH)2)
    • Roughly one-third of the weight of bone is from collagen fibers and non-collagenous proteins, which contribute tensile strength
  • Cells of mature bone
    • Osteoprogenitor cells
    • Osteoblasts
    • Osteocytes
    • Osteoclasts
  • Osteoblasts
    • Secrete the organic components of the bone matrix
    • Found in a single layer on the inner or outer surfaces of a bone
    • Responsible for the production of new bone, a process called osteogenesis
  • Osteocytes
    • Maintain and monitor the protein and mineral content of the surrounding matrix
    • Occupy small chambers called lacunae
    • Channels called canaliculi interconnect the osteocytes situated in adjacent lacunae
  • Osteoclasts
    • Large, multinucleate cells found at sites where bone is being removed
    • Secrete acids to dissolve the bony matrix and release amino acids and the stored calcium and phosphate
  • The balance between the activities of osteoblasts and osteoclasts is very important
  • Compact bone
    • The basic functional unit is the cylindrical osteon or Haversian system
    • Contains a central canal (Haversian canal) that contains blood vessels
    • Perforating canals (Volkmann's canals) extend roughly perpendicular to the surface for blood vessel passage
  • Spongy bone
    • Also termed trabecular bone or cancellous bone
    • Arrangement of parallel struts or thick, branching plates called trabeculae or spicules
    • Numerous interconnecting spaces between the trabeculae
  • Periosteum
    • The outer surface of a bone usually covered by a periosteum
    • Isolates and protects the bone from surrounding tissues
    • Provides a route and a place of attachment for circulatory and nervous supply
    • Actively participates in bone growth and repair
    • Attaches the bone to the connective tissue network of the deep fascia
  • Endosteum
    • Cellular endosteum lines the medullary cavity
    • Contains osteoprogenitor cells, covers the trabeculae of spongy bone, and lines the inner surfaces of the central canals and perforating canals
  • Red and yellow bone marrow
    • Red marrow functions in the formation of red blood cells, white blood cells and blood platelets
    • In infants, red marrow is found in the bone cavities, but is largely replaced by yellow marrow for fat storage in adults
  • Intramembranous ossification
    1. Mesenchymal cells aggregate and differentiate into osteoblasts within embryonic or fibrous connective tissue
    2. Occurs in the deeper layers of the dermis, forming dermal bones like the roofing bones of the skull, mandible, and clavicle
    3. Sesamoid bones form within tendons
  • Factors regulating bone growth
    • Calcium and phosphate salts
    • Magnesium, citrate, carbonate, and sodium ions
    • Vitamins A and C
    • Steroids (e.g. vitamin D)
    • Hormones (e.g. parathyroid, calcitonin, growth hormone, estrogen, testosterone)
  • Cartilage characteristics
    • Mostly water; no blood vessels or nerves
    • Tough, resilient
    • New cartilage forms from chondroblasts
    • Heals poorly
  • Types of skeletal cartilage
    • Hyaline cartilage
    • Elastic cartilage
    • Fibrocartilage