Skeletal System

slideshow

skeletal system

  • composed of the body’s bones and associated ligaments, tendons, and cartilages
  • functions:
    • ^^support^^
    • the bones of the legs, pelvic girdle, and vertebral column support the weight of the erect body
    • the mandible (jawbone) supports the teeth
    • other bones support various organs and tissues
    • ^^protection^^
    • the bones of the skull protect the brain
    • ribs and sternum (breastbone) protect the lungs and the heart
    • vertebrae protect the spinal cord
    • ^^movement^^
    • skeletal muscles use the bones as levers to move the body
    • ^^reservoir for minerals and adipose tissue^^
    • 99% if the body’s calcium is stored in bone
    • 85% of the body’s phosphorous is stored in the bone
    • adipose tissue is found in the marrow of certain bones
      • energy is really being stored
    • ^^hematopoiesis^^
    • aka blood cell formation
      • red blood cells only last about 120 days
    • all blood cells are made in the marrow of certain bones
  • there are 206 named bones in the human body
  • each one belongs to one of 2 large groups
    • axial skeleton
    • forms long axis of the body
    • includes the bones of the skull, vertebral column, and rib cage
    • these bones are involved in protection, support, and other parts of the body
    • appendicular skeleton
  • 4 types of bones
    • ^^long bones^^
    • much longer than they are wide
    • all bones of the limbs except for the patella (kneecap) and the bones of the wrist and ankle
    • consists of a shaft plus 2 expanded ends
    • ^^short bones^^
    • roughly cube shaped
    • bones of the wrist and the ankle
    • ^^flat bones^^
    • thin, flattened, and usually a bit curved
    • scapulae, sternum, ribs, and most bones of the skull
    • ^^irregular bones^^
    • have weird shapes that fit none of the 3 previous classes
    • vertebrae, hip bones, 2 skull bones (sphenoid and the ethmoid bones)
  • bones are organs, composed of multiple tissue types
  • composed of
    • bone tissue (osseous tissue)
    • fibrous connective tissue
    • cartilage
    • vascular tissue
    • lymphatic tissue
    • adipose tissue
    • nervous tissue
  • ^^all^^ bones consist of a dense, solid outer layer known as ^^compact bone^^ and an inner layer of ^^spongy bone^^ - a honeycomb of flat, needle-like projections called trabeculae
  • bone is an extremely dynamic tissue

bone structure

  • bone tissue is a type of connective tissue, so it must consist of cells plus a significant amount of extracellular matrix
  • bone cells
    • osteoblasts
    • bone-building cells
    • osteocytes
    • mature bone cells
    • osteoclasts
    • huge cells derived from the fusion of as many as 50 monocytes

fractures

fracture types

  • open (compound) → bone ends penetrate the skin
  • closed (simple) → bone ends don’t penetrate the skin
  • comminuted → bone fragments into 3 or more pieces (common in elderly)
  • greenstick → bone breaks incompletely. one side bent, one side broken. common in children whose bone contains more collagen and are less mineralized
  • spiral → ragged break caused by excessive twisting forces. sports injury/injury of abuse
  • impacted → one bone fragment driven into the other