Anatomy 101: Skeletal System

Skeletal System

The organ system consisting of bones, cartilage, ligaments, and joints that provides structural support, protection, movement, and mineral storage.

Bone (Osseous Tissue)

A dense, living connective tissue that forms the rigid framework of the skeleton, composed of collagen fibers and calcium phosphate minerals.

Axial Skeleton

The 80 bones forming the central axis of the body, including the skull, vertebral column, and rib cage.

Appendicular Skeleton

The 126 bones of the limbs, pectoral girdle (shoulders), and pelvic girdle (hips) that facilitate movement.

Compact Bone

Dense, hard outer layer of bone tissue organized into osteons (Haversian systems) that provides strength and protection.

Spongy (Cancellous) Bone

Lightweight, porous bone tissue found inside bones that contains trabeculae and red bone marrow for blood cell production.

Periosteum

A tough, fibrous membrane covering the outer surface of bones that contains blood vessels, nerves, and osteoblasts for bone growth and repair.

Osteoblast

A bone-forming cell that synthesizes and secretes the organic matrix of bone (osteoid) and initiates mineralization.

Osteoclast

A large multinucleated cell that breaks down (resorbs) bone tissue, releasing calcium and phosphate into the bloodstream.

Osteocyte

A mature bone cell embedded in the bone matrix that maintains bone tissue and communicates with other bone cells through canaliculi.