The Skeletal System Divisions, Functions, and Classification

(pages 134-137)

axial skeleton

the bones that form the longitudinal axis of the body

appendicular skeleton

the bones of the limbs and girdles that are “appended” (attached) to the axial skeleton

ligaments

fibrous cords that bind the bones together at joints

joints

sites that give the body flexibility and allow movement to occur

Support

function where bones form the internal framework that supports the body and cradles its soft organs

Protection

function where bones protect soft body organs

Movement

function where skeletal muscles use the bones as levers to move the body and its parts

Storage

function where fat is stored in the internal (marrow) cavities of bones, and bone itself serves as a storehouse for minerals, the most important of which are calcium and phosphorus

Blood cell formation (hematopoiesis)

process that occurs within the marrow cavities of certain bones

osseous

relating to bone tissue

Compact bone

dense bone tissue that looks smooth and homogeneous

Spongy bone

bone tissue composed of small needlelike pieces of bone and lots of open space

Long bones

bones typically longer than they are wide, having a shaft with heads at both ends, and mostly composed of compact bone

Short bones

bones that are generally cube-shaped and contain mostly spongy bone (e.g., bones of the wrist and ankle)

Sesamoid (ses′ah-moyd) bones

a special type of short bone that forms within tendons

Flat bones

bones that are thin, flattened, and usually curved, having two thin layers of compact bone sandwiching a layer of spongy bone between them

Irregular bones

bones that do not fit one of the preceding categories (e.g., the vertebrae