The Skeletal System

Flashcards about the skeletal system.

Parts of the Skeletal System

Bones (skeleton), Joints, Cartilages, Ligaments

Two Subdivisions of the Skeleton

Axial skeleton and Appendicular skeleton

Functions of the Bones

Support the body, Protection of soft organs, Allow movement via attached muscles, Store minerals and fats, Blood cell formation (hematopoiesis)

Compact Bone

Dense, smooth, and homogeneous

Spongy Bone

Small needlelike pieces of bone with many open spaces

Classification of Bones by Shape

Long, Flat, Short, Irregular

Long Bones

Typically longer than they are wide, contain mostly compact bone, examples include the femur and humerus.

Flat Bones

Thin, flattened, and usually curved; examples include most bones of the skull, ribs, and sternum.

Short Bones

Generally cube-shaped, contain mostly spongy bone with an outer layer of compact bone; examples include carpals and tarsals.

Sesamoid Bones

Bones that form within tendons

Irregular Bones

Irregular shape, do not fit into other bone classification categories; examples include vertebrae and hip bones.

Diaphysis (Shaft)

Makes up most of bone’s length and is composed of compact bone

Periosteum

Outside covering of the diaphysis made of fibrous connective tissue membrane

Epiphysis (Ends)

Composed mostly of spongy bone enclosed by a thin layer of compact bone

Articular Cartilage

Covers the external surface of the epiphyses, made of hyaline cartilage, and decreases friction at joint surfaces

Epiphyseal Line

Remnant of the epiphyseal plate seen in adult bones.

Epiphyseal Plate

Flat plate of hyaline cartilage seen in young, growing bone that causes lengthwise growth of a long bone.

Endosteum

Lines the inner surface of the shaft and is made of connective tissue.

Medullary Cavity

Cavity inside the shaft that contains yellow marrow (mostly fat) in adults and red marrow for blood cell formation until age 6 or 7.

Bone Markings

Sites of attachments for muscles, tendons, and ligaments; passages for nerves and blood vessels

Projections or Processes

Grow out from the bone surface

Depressions or Cavities

Indentations

Tuberosity

Large, rounded projection; may be roughened

Crest

Narrow ridge of bone; usually prominent

Trochanter

Very large, blunt, irregularly shaped process (the only examples are on the femur)

Line

Any bony prominence less prominent than a crest

Tubercle

Small, rounded projection or process

Epicondyle

Raised area on or above a condyle

Spine

Sharp, slender, often pointed projection

Process

Any bony prominence

Head

Bony expansion carried on a narrow neck

Facet

Smooth, nearly flat articular surface

Condyle

Rounded articular projection

Ramus

Armlike bar of bone

Groove

Furrow

Meatus

Canal- or tunnel-like passageway

Sinus

Cavity within a bone, filled with air and lined with mucous membrane

Fissure

Narrow, slitlike opening

Foramen

Round or oval opening through a bone

Notch

Indentation at the edge of a structure

Fossa

Shallow, basinlike depression in a bone, often serving as an articular surface

Trabeculae

Small, needlelike pieces of bone that compose spongy bone

Osteocytes

Mature bone cells situated in bone matrix

Lacunae

Cavities in bone matrix that house osteocytes

Lamellae

Concentric circles of lacunae situated around the central (Haversian) canal

Central (Haversian) Canal

Opening in the center of an osteon (Haversian system) that runs lengthwise through bone and carries blood vessels and nerves.

Osteon (Haversian System)

A unit of bone containing central canal and matrix rings that serves as the structural and functional unit of compact bone

Canaliculi

Tiny canals that radiate from the central canal to lacunae, forming a transport system connecting all bone cells to a nutrient supply.

Perforating (Volkmann’s) Canal

Canal perpendicular to the central canal that carries blood vessels and nerves.