Human musculoskeletal system

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

The human musculoskeletal system, also called the locomotor system, lets us move and stay upright. It includes bones, muscles, cartilage, tendons, ligaments, joints, and other connective tissues. Its main jobs are to give the body shape and support, allow movement, and protect vital organs. The skeleton also stores minerals and helps make blood.

Two big parts make up the skeleton: the axial skeleton (the skull, spine, and rib cage) and the appendicular skeleton (the shoulders, arms, hips, and legs). Bones come in five general types: long, short, flat, irregular, and sesamoid. When we are born, we have more than 300 bones, but many fuse as we grow, so adults usually have about 206 bones.

Bones hold the body up and protect organs. They store minerals like calcium and phosphorus. Inside some bones is red bone marrow, which makes blood cells. Other bone marrow (yellow marrow) stores fat and can be used for energy if needed.

Muscles power movement and come in three kinds: skeletal, cardiac, and smooth. Skeletal muscles attach to bones and move the body; cardiac muscle pumps the heart; smooth muscles control the movement of substances inside hollow organs. Only skeletal muscles are under conscious control.

Tendons are strong bands that connect muscles to bones. When a muscle contracts, the tendon pulls on the bone, making movement. Tendons can stretch and act like springs, helping save energy during movement.

Joints are where bones meet. They can be highly mobile (diarthroses), somewhat movable (amphiarthroses), or mostly immovable (synarthroses). Most movable joints are lubricated by synovial fluid inside a joint capsule, which reduces friction. Ligaments are tough bands that connect bones at joints and help stabilize them, while cartilage covers the ends of bones to prevent grinding.

Bursae are small fluid-filled sacs near joints that cushion movement between bones and soft tissues.

Because the musculoskeletal system works with other body systems, problems in one area can affect movement and health. Common issues include joint disorders, muscle diseases, and nerve-related problems. Treatments for complex cases are usually provided by specialists in physical medicine and rehabilitation or by orthopedic surgeons.

Occasionally, conditions such as pelvic girdle pain during pregnancy involve multiple factors—nerves, muscles, ligaments, and posture—leading to pain and reduced function.