The Skeletal System

Flashcards covering the key vocabulary and concepts related to the skeletal system.

Skeletal System

Consists of bones, joints, cartilages, and ligaments. It is divided into the axial and appendicular skeleton.

Functions of Bones

Support the body, protect soft organs, allow movement, store minerals and fats, and facilitate blood cell formation (hematopoiesis).

Compact Bone

Dense, smooth, and homogeneous bone tissue.

Spongy Bone

Bone tissue with small needlelike pieces and many open spaces.

Long Bones

Typically longer than they are wide, consist of a shaft with enlarged ends, and contain mostly compact bone with spongy bone at the ends (e.g., femur, humerus).

Flat Bones

Thin, flattened, and usually curved, with two thin layers of compact bone sandwiching a layer of spongy bone (e.g., skull bones, ribs, sternum).

Short Bones

Generally cube-shaped and contain mostly spongy bone with an outer layer of compact bone (e.g., carpals, tarsals).

Irregular Bones

Bones with irregular shapes that do not fit into other classification categories (e.g., vertebrae, hip bones).

Diaphysis

The shaft of a long bone, composed of compact bone.

Periosteum

The outside covering of the diaphysis, made of fibrous connective tissue.

Epiphysis

The ends of a long bone, composed mostly of spongy bone enclosed by a thin layer of compact bone.

Articular Cartilage

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

Epiphyseal Line

Remnant of the epiphyseal plate in adult bones.

Epiphyseal Plate

Flat plate of hyaline cartilage seen in young, growing bone. 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 of a long bone, containing yellow marrow (mostly fat) in adults and red marrow for blood cell formation until age 6 or 7.

Tuberosity

Large, rounded projection; may be roughened.

Crest

Narrow ridge of bone; usually prominent.

Trochanter

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

Line

Narrow ridge of bone; 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.

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.

Fossa

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

Foramen

Round or oval opening through a bone.

Trabeculae

Small, needlelike pieces of bone that make up 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, running lengthwise through bone, carrying blood vessels and nerves.

Osteon (Haversian System)

A unit of bone containing a central canal and matrix rings; the structural and functional unit of compact bone.

Canaliculi

Tiny canals radiating 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, carrying blood vessels and nerves.