Skeletal System and Bone Structure

Flashcards about the skeletal system and bone structure for exam review.

Skeletal System

Includes all of the bones, cartilages, and ligaments of the body that support and give shape.

Axial Skeleton

The vertical, central axis of the body, including bones of the head, neck, chest, and back.

Appendicular Skeleton

Includes bones of the upper and lower limbs, plus the bones that attach each limb to the axial skeleton.

Pectoral Girdle

Anchors the upper limb to the thoracic cage of the axial skeleton.

Pelvic Girdle

Attaches the lower limb to the vertebral column.

Long Bone

Cylindrical shape and longer than it is wide, functions as levers.

Short Bone

Cube-like shape, approximately equal in length, width, and thickness, provides stability and support.

Flat Bone

Typically thin, often curved, serves as points of attachment for muscles and often protects internal organs.

Irregular Bone

Does not have any easily characterized shape and therefore does not fit any other classification.

Sesamoid Bone

Small, round bone shaped like a sesame seed, protects tendons by helping them overcome compressive forces.

Diaphysis

Tubular shaft that runs between the proximal and distal ends of the bone.

Epiphysis

Proximal and distal ends of the bone.

Medullary Cavity

Hollow region in the diaphysis, filled with yellow marrow in adults.

Compact Bone

Dense and hard type of bone that composes the walls of the diaphysis.

Endosteum

Delicate membranous lining of the medullary cavity, where bone growth, repair, and remodeling occur.

Periosteum

Fibrous membrane covering the outer surface of the bone, contains blood vessels, nerves, and lymphatic vessels.

Articular Cartilage

Thin layer of cartilage that reduces friction and acts as a shock absorber where epiphyses meet other bones.

Diploë

Spongy bone in flat bones, lined on either side by a layer of compact bone.

Articulation

Where two bone surfaces come together.

Projection

Area of a bone that projects above the surface of the bone, attachment points for tendons and ligaments.

Hole

Opening or groove in the bone that allows blood vessels and nerves to enter the bone.

Hydroxyapatite

Crystallized matrix of collagen fibers and inorganic salt crystals that gives bones hardness and strength.

Osteogenic Cells

Undifferentiated bone cells with high mitotic activity, found in the deep layers of the periosteum and the marrow.

Osteoblasts

Responsible for forming new bone, found in the growing portions of bone, including the periosteum and endosteum.

Osteocyte

Primary cell of mature bone, maintains the mineral concentration of the matrix.

Osteoclast

Cell responsible for bone resorption, or breakdown.

Osteon (Haversian System)

The microscopic structural unit of compact bone.

Lamellae

Concentric rings of calcified matrix in compact bone.

Central Canal

Contains blood vessels, nerves, and lymphatic vessels in compact bone.

Lacunae

Spaces where osteocytes are located in compact bone.

Canaliculi

Connects with the canaliculi of other lacunae and eventually with the central canal in compact bone.

Trabeculae

Network of matrix spikes in spongy bone.