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)
Microsoft Word Version of this document
return to top | next page