Skeletal System

Skeletal System

The framework of the body consisting of bones, joints, cartilages, and ligaments.

Axial Skeleton

The subdivision of the skeletal system that includes the skull, vertebral column, and ribcage.

Appendicular Skeleton

The subdivision of the skeletal system that includes the bones of the limbs, pectoral girdle, and pelvic girdle.

Compact Bone

Dense bone tissue that is homogeneous and forms the outer layer of bones.

Spongy Bone

Bone tissue that consists of small needle-like pieces with many open spaces.

Long Bones

Bones that are typically larger than they are wide and have a shaft with heads at both ends.

Short Bones

Cube-shaped bones that contain mostly spongy bone.

Flat Bones

Thin, flattened, and usually curved bones that have two thin layers of compact bone surrounding a layer of spongy bone.

Irregular Bones

Bones that have an irregular shape and do not fit into other bone classification categories.

Diaphysis

The shaft of a long bone composed of compact bone.

Epiphysis

The ends of a long bone composed of mostly spongy tissue.

Periosteum

The outside covering of the diaphysis, a fibrous connective tissue membrane.

Articular Cartilage

The hyaline cartilage that covers the external surface of the epiphysis, decreasing friction at joint surfaces.

Epiphyseal Plate

A flat plate of hyaline cartilage seen in young, growing bones.

Medullary Cavity

The cavity inside the shaft of a long bone that contains yellow marrow in adults and red marrow in infants.

Osteon (Haversian System)

A unit of bone containing a central canal and matrix ring.

Lacunae

Cavities in bone tissue that contain bone cells (osteocytes) and are arranged in concentric rings.

Canaliculi

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

Bone Fracture

A break in a bone.

Reduction

The process of realigning broken bone ends and immobilizing them for proper healing.

Hematoma

A blood-filled swelling that forms at the site of a bone fracture.

Callus

Fibrocartilage that splints the broken bone to form a temporary patch.

Bony Callus

The replacement of the fibrocartilage callus with hard bone tissue during the repair of a bone fracture.

Pectoral Girdle

The shoulder girdle composed of the clavicle and scapula bones.

Pelvic Girdle

The hip girdle formed by the two coxal bones.

Femur

The thigh bone, the longest and strongest bone in the body.

Tibia

The shinbone, the larger and medial bone of the lower leg.

Fibula

The thin and sticklike bone of the lower leg.

Tarsals

The bones of the ankle.

Metatarsals

The bones of the foot between the ankle and the toes.

Synarthroses

Immovable joints.

Amphiarthroses

Slightly movable joints.

Diarthroses

Freely movable joints.

Fibrous Joints

Joints where bones are united by fibrous tissue, allowing little to no movement.

Cartilaginous Joints

Joints where bones are connected by cartilage, allowing limited movement.

Synovial Joints

Freely movable joints where articulating bones are separated by a joint cavity filled with synovial fluid.

Articular Cartilage

The hyaline cartilage that covers the ends of bones in synovial joints.

Bursae

Flattened fibrous sacs lined with synovial membranes and filled with synovial fluid, providing cushioning and reducing friction in joints.

Tendon Sheath

An elongated bursa that wraps around a tendon, reducing friction as the tendon moves.

Osteoporosis

A bone-thinning disease that makes bones fragile and prone to fractures, commonly affecting older individuals.