Skeletal System

Skeletal System

The body’s framework of bones and connective tissues providing support, protection, and movement.

Axial Skeleton

Skull, vertebral column, ribs, and sternum; supports and protects vital organs.

Appendicular Skeleton

Limbs and girdles; allows movement.

Functions of Skeleton

Support, protection, movement, mineral storage, blood cell formation, fat storage.

Hematopoiesis

Formation of blood cells in red bone marrow.

Compact Bone

Dense bone tissue forming the outer layer of bone.

Spongy Bone

Porous bone tissue that contains red bone marrow.

Osteocyte

Mature bone cell that maintains bone tissue.

Osteoblast

Bone-forming cell.

Osteoclast

Bone-destroying cell that breaks down bone matrix.

Diaphysis

Shaft of a long bone.

Epiphysis

Ends of a long bone.

Metaphysis

Region between diaphysis and epiphysis.

Periosteum

Tough outer covering of bone.

Endosteum

Inner lining of bone cavity.

Medullary Cavity

Central cavity of bone that contains marrow.

Articular Cartilage

Smooth cartilage covering bone ends; reduces friction in joints.

Lamellae

Concentric layers in compact bone.

Haversian Canal

Central canal in bone containing blood vessels and nerves.

Long Bone

Bone longer than it is wide (e.g., femur, humerus).

Short Bone

Cube-shaped bone (e.g., carpals, tarsals).

Flat Bone

Thin, flat bone (e.g., skull, ribs).

Irregular Bone

Complex-shaped bone (e.g., vertebrae).

Sesamoid Bone

Bone embedded in tendon (e.g., patella).

Synarthrosis

Immovable joint (e.g., skull sutures).

Amphiarthrosis

Slightly movable joint (e.g., vertebrae).

Diarthrosis

Freely movable joint (e.g., synovial joints).

Synovial Joint

Joint cavity filled with fluid allowing free movement.

Ball-and-Socket Joint

Joint allowing movement in all directions (shoulder, hip).

Hinge Joint

Joint allowing bending and straightening (knee, elbow).

Pivot Joint

Joint allowing rotation (atlas-axis).

Gliding Joint

Joint allowing sliding movement (carpals).

Saddle Joint

Joint in thumb allowing grasping.

Condyloid Joint

Joint in wrist allowing circular motion.

Fracture

Break in bone.

Osteoporosis

Loss of bone density.

Arthritis

Inflammation of joints.

Scoliosis

Lateral curvature of the spine.

Kyphosis

Hunchback curvature of spine.

Lordosis

Excessive inward curvature of spine.

Rickets

Bone softening due to vitamin D deficiency.