Skeleton

Skeleton consists of 206 bones in adults, divided into the axial skeleton—skull, vertebral column, and rib cage—and the appendicular skeleton comprising the shoulders, pelvis, and limbs. Bones are living tissues, rich in blood supply, that grow, repair, and remodel throughout life. Joints between bones range from immovable sutures in the skull to freely moving synovial joints such as knees and wrists.

Bones protect vital organs: the skull guards the brain, the rib cage shields the heart and lungs, and the vertebral column encases the spinal cord. Long bones like the femur act as levers for muscles to generate motion. Within their medullary cavities lies marrow that produces blood cells and stores fat, linking the skeletal and circulatory systems.

The skeleton stores calcium and phosphorus, releasing them when blood levels drop and absorbing them when levels rise. Hormones such as parathyroid hormone, calcitonin, and vitamin D coordinate this mineral balance. The bones' outer cortical layer provides rigidity, while inner trabecular bone absorbs shock, making the structure both strong and relatively light.

Cartilage cushions joints, and ligaments connect bone to bone, stabilizing movement. As people age or experience heavy use, joints can wear down, leading to conditions like osteoarthritis. weight-bearing exercise, balanced nutrition, and safe movement help maintain bone density and joint health.

Scientists study the skeleton to understand evolution, diagnose diseases, and develop treatments such as joint replacements, bone grafts, and bioengineered scaffolds. Public health efforts encourage regular bone-density screenings, fall prevention, and adequate calcium and vitamin D intake to reduce fracture risk.