Skeletal System

 

The skeleton system is made of 206 bones that are connected at joints or articulations.

• The skeleton is divided into 2 divisions
• • The axial skeleton (skull, vertebral column, ribs, and sternum)
  • The appendicular (arms and legs)
• Bone surfaces are not featureless and smooth.  Bones have bone markings, bumps, holes, and ridges.
• Bone markings fall into 2 categories, projections or processes that grow out from the bone and serve as the site of muscle attachment or helps form joints; and depressions or cavities, indentions or openings in the bone that serves as passageways for nerves and blood vessels.
• There are 2 basic types of osseous tissue:
• • Compact bones are dense and look homogenous
  • Spongy bones are composed of small trabeculae (needlelike bars) of bones and lots of open space.
• Bones also maybe classified by their gross anatomy into 4 groups (type):
• • Long bones: mostly compact, consists of a shaft with head at either end, with longer than they are wide (femur and finger bones)
  • Short bones: cubed-shaped, contains more spongy bone than compact bone (tarsal, carpals)
  • Flat bones: thin bones, contains a layer of spongy bones between 2 wafer-like layers of compact bones (skull bones)
  • Irregular bones: are bones that are compact in structure and do not fall into any of the three categories listed above (vertebrae)
• Nearly every bone in the body is connected to or forms a joint with at least one other bone.  Joints may be classified by structure or functions.
• Structural classification is based on what separates the articulating bones
• • Fibrous
  • Cartilaginous
  • Synovial
• Functional classification focuses on the amount of movement the joint allows
• • Synarthrose (immovable joint)
  • Amphiarthrose (slightly moveable joint)
  • Diarthrose (freely movable joint)

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